Astronomy

Is it possible that Titan is a kuiper object captured by Saturn?

Is it possible that Titan is a kuiper object captured by Saturn?


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I think Titan may be just captured by Saturn, not formed with Saturn together, because:

  1. It has so much nitrogen and methane, which is similar to Pluto and Triton

  2. Except Titan, other moons of Saturn are very small, which other moons may be ejected by Titan during capturing process, similar to Triton and Neptune

  3. According to Nice model, Neptune swapped position with Uranus, while Saturn pulled Jupiter away from the Sun, so I think the orbit of Neptune and Saturn is quite close at past, so if Neptune can capture kuiper object, Saturn also can

Is it possible that Titan was a Kuiper object?


Titan is roughly ten times more massive than Pluto or Eris, the most massive known Kuiper Belt objects (KBOs). (Titan is in fact more massive than any other moon in the Solar System except Ganymede.) It would be a rather strange coincidence if the object that was by far the most massive of the KBOs was in orbit around Saturn, well interior to the Kuiper Belt.

Titan's orbit is prograde (it orbits in the same direction that Saturn rotates) and barely tilted with respect to Saturn's equator (less than half a degree), the rings, and most of the other moons. That strongly suggests it formed out of an accretion disk around Saturn, as the Galilean moons formed around Jupiter.

Titan also has an extremely dense atmosphere, unlike any of the KBOs.

So it's rather unlikely that Titan is a captured KBO.

(Neptun's moon Triton, by the way, is thought to be a captured KBO. But it is only slightly more massive than Eris or Pluto, and it has a peculiar retrograde orbit that is very difficult to explain if it formed around Neptune, but easier to explain if it was captured. And since Neptune is the furthest out of the (known) major planets, it's not that surprising that it could have captured a KBO.)


What Has Cassini-Huygens Discovered on Titan?

Titan has captivated people since its discovery by Christiaan Huygens in 1656. Not much headway was made into the moon until the 1940s when scientists found that Titan had an atmosphere. After 3 flybys (Pioneer 11 in 1979, Voyager 1 in 1980, and Voyager 2 in 1981), scientists wanted even more data (Douthitt 50). And though they had to wait nearly a quarter of a century, the wait has been worth it.

Huygens landed on the moon Titan on January 14, 2005. The probe was a near failure, however, because of communication difficulties. Two radio channels were designed to relay data from Huygens to Cassini, but only 1 was operating properly. That meant half of the data would be lost. The reason for the goof was even worst: The engineers had simply forgotten to program Cassini to listen in for the other channel (Powell 42).

Fortunately, radio technology had improved so much that the team on Earth was able to instruct Huygens to send most of that data from the other channel straight to Earth. The only casualty would be the photographs, so only half were retrievable. This made panorama shots difficult at best (43).

The probe, which weighed in at 705 pounds, fell through Titan&aposs atmosphere at a nice pace of 10 miles per hour. When it landed, it hit a hard layer about half an inch in thickness, then sank in about 6 inches further. Huygens found that Titan has a primarily methane atmosphere, a surface pressure reading of 1.5 bars, 1/7 Earth&aposs gravity, air density that is four times as much as Earth&aposs, winds measure at 250 mph in the upper atmosphere and the surface has many Earth-like features such as riverbeds, hillsides, coastlines, sandbars, and also erosion. At first, it was not clear what was causing this, but after noting the temperatures near negative 292 degrees F, that the hard crust was observed to give off methane and water vapor, and chemical analysis, it was found that Titan has a precipitation system based off methane. Titan is so cold that methane, normally a gas on Earth, was able to achieve liquid state. Further data indicated that a type of volcanism could be occurring involving ammonia and water-ice. This was based off trace amounts of argon found in the air (Powell 42-45, Lopes 30).

Many of these revelations of Titan are just coming to light because of that thick atmosphere. The SAR instrument on Cassini revealed details of the surface at a rate of 2% coverage during each pass as it probes through all the atmosphere. In fact, it is so thick that little sunlight makes it to the surface. Yet after the second flyby of Cassini in February of 2005 and close-ups of the equator in October of 2005, Titan was found to have parallel line features that were in fact dunes. But those require winds and therefore sunlight, of which little should reach the surface. So what causes the winds? Possibly Saturn&aposs gravity. The mystery is ongoing, but those winds are powerful (only 1.9 miles per hour, but remember Titan has a dense atmosphere) yet are only 60% as strong as what the dunes require. Despite that, Titan actually loses some of its atmosphere to the high polar winds, according to Cassini&aposs CAPS instrument. It detected up to 7 tons of hydrocarbons and nitrates every day escaping the clutches of Titan&aposs poles, floating off into space. Some of that haze does fall back to the surface, where through the erosion of methane rain could form the sand and possible wind systems (Stone 16, Howard "Polar," Hayes 28, Lopes 31-2, Arizona State University).

Further flybys revealed that the dunes do indeed change shape and seem to travel in a process known as saltation, or "jumping," which needs high wind velocities and dry material. Some models indicate that as sand strikes other sand particles, the collision sends enough flying into the air that the jump can occur, but only for those particles near the surface of the dune. And depending on the direction of the wind, different dunes can form. If they blow in one direction, you get transverse dunes which run perpendicular to the direction of the wind. However, if multiple winds are present, then you get longitudinal dunes, whose line matches the average wind direction (Lopes 33).

On Titan, a majority of the dunes are longitudinal in nature. Dunes make up 12-20% of the surface of Titan and with 16,000+ seen, there is no shortage of variety. In fact, a majority can be found +/- 30 degrees above and below the equator with some even being as far as 55 degrees. And based on the overall pattern of the dunes, the winds on Titan should be west to east. However, rotation models (which transfer angular momentum to surface direction) point to a east to west wind system. And Huygens measured winds going in a SSW direction. What gives? The key is remembering the majority of the winds are longitudinal and therefore have many different winds at play. In fast, models built by Tetsuya Tokano (from the University of Colongne in Germany) and Ralph Lorenz (from John Hopkins) show that indeed the moon should have east to west direction but that occasional west to east winds do occur near equator and form the dunes we have seen (Lopes 33-5).

A piece to the puzzle may surprise you: static electricity. Theory shows that as the sands of Titan blow around, they rub and generate a slight charge. But given the right interactions, the sands can accumulate and lose their charge, being dumped in certain locations. And the hydrocarbons present on the surface are not good conductors, encouraging the sands to discharge only with each other. How this fully interplay with the winds on Titan remains to be seen (Lee).

The entre surface of Titan revealed.


An image of Saturn, taken by the Cassini probe on Feb. 19, 2016. The spacecraft captured this image from roughly 1.2 million miles, at 7 degrees above the ring plane using its wide-angle camera. The moon Dione can be seen in the lower left of the image. Read the full story here.

Saturn's dark side looms large in this image taken by the Cassini spacecraft in January 2015. Barely visible in the bottom-left corner is Tethys, one of Saturn's moons. The rings of Saturn are a dazzling accessory in this image from Cassini. Read the full story behind the photo.


Is it possible that Titan is a kuiper object captured by Saturn? - Astronomy

Is Pluto a real planet, or just a large asteroid? What is the definition of a planet, anyway?

The question of whether Pluto is or is not a planet is very popular among the public. However, most professional astronomers do not think this is a question of that much importance, as the dividing line between a planet and an asteroid is somewhat arbitrary. Still, there are good arguments for supporting either view:

1) Historical. Pluto was discovered long before other Kuiper Belt Objects (large asteroids that orbit in the same region) and at that time "planet" was the only available label for something like Pluto. So people argue that since there is nothing to gain from demoting Pluto, we should just leave the things as they are.

A weakness in this argument is that demotions are sometimes necessary if an important observational result is proven wrong (i.e. object is actually much smaller than we though). From its discovery in 1930, and up until 1978 when Pluto's moon Charon was discovered, Pluto was though to be larger than Mercury and possibly even Mars (in reality, it's much smaller in mass than either of them). Would the astronomers designate Pluto a planet in 1930 if they knew how small it really was? I think that the answer is still yes, but there is no real way to confirm that.

2) Size. Pluto's mass is 25 times smaller than Mercury's and only 9 times larger than that of Ceres, the largest body in the asteroid belt. Some recent large Kuiper Belt Objects (notably Sedna) are likely larger than Ceres, if smaller than Pluto (and the recently discovered Eris (previously "Xena" or 2003 UB313) may be larger than Pluto). However, any lower cutoff in size for planets is arbitrary, and putting it above or below Pluto's size and mass is a question of individual preference. Also, if, for example, the lowest diameter a planet can have is 2000 km, then a body with diameter of 2001 km in a planet while a body with 1999 km diameter is an asteroid. To make things worse, planetary diameters are rarely known that accurately before direct exploration by spacecraft, which is not always an option.

3) Environment. Our solar system can be roughly divided into two kinds of regions: those where major planets orbit, which are mostly free of small bodies, and the regions where there are no planets and where many small bodies orbit (the examples of the latter are the asteroid belt and the Kuiper belt). While this division is not perfect (comets and some asteroids do cross planetary orbits, but these are few and their orbits are unstable), it does reflect an importanty fact that a planet's gravity strongly influnces its surroundings, while asteroids affect each other mainly by direct collisions.

Mike Brown of Caltech and his colleagues have recently proposed that population of small bodies which may share the orbit with the candidate body should be taken into account when defining a planet. They propose that if a body's mass is greater than the total mass of small stuff which orbits in the same region, it is a planet. So, Mercury might not be too big, but since very few asteroids orbit the Sun in its vicinity, it is definitely a planet. Jupiter shares its orbit with numerous so-called Trojan asteroids, but their total mass is negligible compared with that of Jupiter, so Jupiter is also a planet. Pluto, according to this criterion, is not a planet, because its mass is smaller than the estimated total mass of all other Kuiper Belt Objects.

The theory behind this definition is that once an object is large enough it would "sweep up" smaller bodies in its vicinity, leaving its orbit empty except for itself, few transient interlopers (comets etc.) and maybe a resonant population with a small mass (e.g. Trojans). Eight major planets managed to do this, but not Pluto, which is not a major influence on the Kuiper Belt.

While this definition of a planet is probably the most objective one proposed so far, there might be practical problems with it. It is unrealistic to expect that a classification of a body has to be delayed until the neighboring region has been thoroughly explored. This might not be possible for decades in the case of most extrasolar planets, or even some very distant bodies in our solar system (like Sedna, for example).

The bottom line is that if Pluto were discovered now, most likely we would not call it a planet. However, most astronomers think that a change in Pluto's status would be of limited usefulness while confusing, so it will probably continue to be considered a planet. The exact and universal criteria on what constitutes a planet are not agreed upon yet, and we might need to wait for many years until most scientists agree on one.

Update Aug 2006 by Karen Masters: The International Astronomical Union (IAU) voted this month to redefine a planet much a long the lines that Matija discusses above. There is both a size limit, and a requirement that the object sweep out its orbit. In addition the object must independently orbit the Sun (excluding several large moons of Jupiter). This new classification redefines Pluto as a "dwarf planet", leaving the Solar System with 8 "classical planets". New additions to the dwarf planet class are Sedna, the largest asteroid, Ceres and Eris (previously "Xena" or 2003 UB313). Many more objects may join the class, pending more accurate determinations of their size, including Quaoar, and several other Kuiper belt objects. This definition followed an earlier suggestion that all objects independently orbiting the Sun which have sufficient gravity to become roughly circular should be called planets - such a definition could have dramatically increased the number of planets. Dynamical astronomers (like Matija) argued that the orbital criteria (that the object dominate its orbit) was equally important, thus excluding Pluto, and these many other small objects from the "classical" planets.

This new definition of planets which exludes Pluto has caused a lot of interest and discussion, with Astronomers and the general public alike coming out loudly on both sides of the argument. I think it's safe to say that any decision by the IAU would have upset someone, but putting the definition of a planet on an objective scientific footing will likely (ultimately) be popular with Astronomers. Pluto will always retain a special place in our hearts, having been considered a planet for over 3/4 of a century and with a NASA mission (New Horizons) on its way to reach the Pluto-Charon system in July 2015, Pluto will not be forgotten.

This whole episode also gives an interesting insight into the scientific process of object classification and the changes which must be made to schemes in the light of new scientific information.

About the Author

Matija Cuk

Matija works on the orbital dynamics of the lesser moons of Jupiter and Saturn. He graduated with his PhD from Cornell in November 2004 and is now working at the University of British Columbia in Canada.


The Unlikely King of the Kuiper Belt

Although the innermost planets, from Mercury through Saturn, were known since ancient times, it's only since the advent of the telescope that we've discovered what really lives in our Solar System. Over the past four centuries, the wonders of not only the distant Universe, but also our nearby neighborhood, have been uncovered in spectacular detail.

The third and fourth largest planets were discovered, as were a plethora of moons around other worlds, a belt of asteroids between Mars and Jupiter (at the ice-line of our Solar System, or where the strength of the Sun is insufficient to move water out of its solid phase), and a Kuiper belt out beyond the final planet. (And the Oort cloud even beyond that!)

Although Uranus was discovered in 1781 by William Herschel and its bizarre failure to adhere to Kepler's laws led to the prediction-and-discovery of Neptune in 1846, it wasn't until 1930 that a lone astronomer, looking at pairs of images taken at different times, happened upon the serendipitous discovery of a lifetime.

Even though it was the only world located out beyond the orbit of Neptune for nearly 50 years (until Pluto's largest moon, Charon, was discovered), it was recognized relatively quickly that Pluto was a harbinger for many more such objects, now recognized (and confirmed, since 1992) to be just one of a great many located in the Kuiper Belt. The other bodies began to exhibit a variety of sizes, shapes, and orbital characteristics, although they all had a number of properties that threw Pluto's "privileged" status as a "planet" into question:

  • similar, trans-Neptunian orbits in the same direction and with similar periods,
  • masses and sizes of the same order-of-magnitude as Pluto,
  • Pluto-like densities and surface properties, with lots of surface methane ice,
  • similar atmospheric compositions to Pluto, as seen by occultations, and
  • numbers that grew from "a few" to "dozens" to more than a thousand as of today.

This all came to a head in 2005, when it was discovered that Pluto isn't even the most massive object in the Kuiper Belt!

That distinction belongs to Eris, which weighs in at about 127% the mass of Pluto. That discovery paved the way for a new classification scheme that included an additional class of Solar System objects known as dwarf planets, of which Eris and Pluto are the two most massive at the present time.

But when it comes to the King of all Kuiper Belt objects, none of these little monsters can stake that claim. Because there's one object that we don't normally think of as a Kuiper Belt object that has them all beat.

This is Neptune, the outermost planet in our Solar System. No, it doesn't qualify as a Kuiper Belt object it's a planet, just like you've always learned. But back in 1846, there were some awfully powerful telescopes in the world, certainly much better and bigger ones than were around in 1781 (when Uranus was discovered) or at any time before that. Back in 1781, there was only one telescope in the world -- commissioned in 1780 -- that had a primary mirror of two feet (61 cm) or more in diameter.

By time 1846 came around, the largest telescope in the world had a primary mirror that was six feet (1.8 meters) in diameter, and amateurs with no formal training -- like William Lassell -- were building their own two foot diameter telescopes themselves.

The timetable for the discovery of Neptune was swift: Urbain Le Verrier announced his prediction for the undiscovered planet's position on August 31, 1846, and composed a letter to Johann Galle, director of the Berlin observatory. Galle and his assistant, Heinrich d'Arrest, looked for the planet on September 23, and discovered it that very night in one of the greatest accomplishments of all-time in theoretical astrophysics.

But news traveled fast, and back in England, William Lassell was eager to view the newly-discovered world.

Just 17 days after the discovery of the hypothesized new world that had occupied many of the world's greatest professional astronomers for decades, a virtually unknown and amateur telescope-maker discovered Triton, by far the largest satellite world of Neptune. (Although to be fair, it was the largest telescope in England at the time.) If all the Solar System's moons were compared to one another, Triton would be the seventh largest in size, behind only Earth's Moon, Saturn's Titan, and the four Jovian moons discovered by Galileo.

But -- up close -- Triton doesn't look like any other large moon in the entire Solar System! For one, every other large moon revolves around its planet the same way all the planets revolve around the Sun: counterclockwise, as viewed if you flew directly upwards above the Earth's north pole. But not Triton, which revolves around Neptune in the opposite direction!

In terms of density, it resembles Pluto far more than it resembles either Neptune or any other Moon in the Solar System. And in terms of atmospheric composition, it's virtually identical to the known worlds found in the Kuiper Belt.

That Triton isn't a naturally occurring moon of Neptune, but has been gravitationally captured (by the same mechanism described here last week) from its place of origin: the Kuiper Belt. Even though it isn't currently in the Kuiper Belt, that doesn't stop it from being the largest, most massive, most accessible, first-discovered, and in many subjective ways, greatest Kuiper Belt Object of them all!

But it's real, it's spectacular, and unlike every other Kuiper Belt Object (so far), we've been there! That was thanks to Voyager 2 in 1989 take a look at this photo mosaic of a large chunk of its surface!

If it looks cantaloupe-like to you away from the poles, well done that's the semi-official NASA term for it! So the next time you think about worlds from beyond our planets, don't just think of frozen ice-and-rock-balls orbiting in deep space, nor only of the comets disturbed by passing gravitational bodies and hurled inwards towards the Sun, but also of the rogue worlds that migrate inwards and wind up captured by gas giants.

After all, if you didn't include them, you'd be missing out on Triton, largest of all the trans-Neptunian objects and the onetime King of the Kuiper Belt!

More like this

Very interesting. I hadn't seen this pic of Triton before. Do we have any idea of what makes the cantaloupe texture? Ice expansion of some sort, but certainly not water. It looks like there's highlands on the bottom of the pic, with some black smudges from what I assume are volcanic vents? It looks like they blow in the same direction. Does Triton have an atmosphere?

Too bad that in a few more billion years Triton will plunge into Neptune.

Dan, we will nudge a few small Kuiper belt objects into Triton to counteract tidal friction :)

-Ethan, there will be many more objects in the "scattered disc" component. Using the orbit of 1996TL66 as an example, a lot of BIG objects will be out there at 130 AU, and even if they are larger than Triton we will not see then until they return to perihelion. in a thousand years.

An object can be both a Kuiper Belt Object and a planet. Such are Pluto, Haumea, Makemake, and Eris, and even Charon, which can be considered part of the binary Pluto-Charon system. One classification does not preclude the other. The Kuiper Belt does not lie beyond the "final planet" it includes the final planet, which currently is Eris. Also, Eris is 27 percent more massive than Pluto, not 127 percent more massive. Triton is likely a captured Kuiper Belt Object, but since it is massive enough to be rounded by its own gravity, it can also, like all spherical moons, be considered a satellite planet.

Ethan said Eris "weighs in at about 127% the mass of Pluto" which is the same as saying "27% more massive".

And that's one possible classification system, sure, but not the one in use. You could define everything that is round due to its gravity as a "planet" but I find it useful to distinguish between a planet and their satellites. Why not just call all round objects "round objects" rather than using the term planet? I also find it useful to distinguish between objects which gravitationally dominate their orbit and do not. This is the historical though unofficial way 'planet' was used Pluto isn't the first object to be "downgraded" from planet once it was discovered to not be the dominant object in its orbit.

Of course this is just applying names to sets of properties for the sake of simplifying discussion and satisfying the human urge for classification.

The ultimate would be to eschew any nomenclature, and simply talk about "the set of objects with the following properties: < round, orbits a body other than the sun, icy >" rather than creating a special name for large icy moons, just as an example.

But we love the word "planet" for some reason.

"Why not just call all round objects “round objects” rather than using the term planet? "

Because a baseball is not a planet.

We already have a term for these things like Mars, Earth, Jupiter, and so on: planets.

We have to define what we mean by the word and as we find cases where the use of the word as defined leads to it being pointless, we refine the definition.

Planet used to mean "wanderer".

"simply talk about “the set of objects with the following properties: < round, orbits a body other than the sun, icy >” "

You obviously have a different definition of the term "simple".

How about we talk about "the planets"?

Isn't that simpler? It's a hell of a lot less word use.

and since "icy" is a solid state of water, cold compared to human comfort or a "hard stare", you have to define "icy".

And the definition of "set"

"The Kuiper Belt does not lie beyond the “final planet” it includes the final planet, which currently is Eris. "

Obviously, under the modern understanding of what a planet is, Pluto, Eris, etc. are not planets. However, is it possible that there could be a trans-Neptunian planet that has so far remained undetected? Or would a body large enough to clear its orbit be detectable via gravitational interaction on Neptune, Pluto, Eris or other outer solar system bodies? I guess such a hypothetical planet could not be located in the Kuiper belt since then it could not be said to have cleared its orbit, but could such a planet exist beyond the Kuiper belt without being detectable via interaction with known bodies?

I hope that we get to have orbiters around the ice giants - and Triton in my time.

"Because a baseball is not a planet."

Yes, to be precise I'd say "hydrostatic equilibrium", which you can understand "round" to mean in this context*. But also the moon is not a planet in our current nomenclature, so "planet" is not a replacement for the concept of objects in hydrostatic equilibrium.

If you noticed, they were in essence proposing a new system of nomenclature where everything that is round is a planet. That is not the current definition, but it could be. The thing is, why use the word "planet" just to mean "round" when we already have "round". If we're going to use the word "planet" it should (and of course does) mean more than that.

"How about we talk about “the planets”?"

Because if you noticed, the set of objects I described are not planets or even a subset of planets. :P

The point is that "planet" describes only one interesting subset of properties objects can have in common. If you gave a name to every subset of properties someone might be interested in, you'd have a ridiculous number of names that nobody could possibly remember and it'd be anything but simple. And why get hung up on the nomenclature anyway since whatever set of properties you decide defines "planet", objects still have the exact same properties?

Of course I like the word "planet" and the current definition, but I know that's because of history and culture as much as anything. It's why so many people shit a brick over the "demotion" of Pluto -- "planet" has cachet that has nothing to do with the significance of specific objects or specific properties.

But if what I care about is objects that are round and orbit the sun, but not whether they cleared their orbit, then the term "planet" is useless because it's just a subset of what I'm interested in. I'd have to say "planets and". Or if I'm just interested in rocky bodies I'd have to say "rocky planets and. " then enumerate all the things that define the "and" to complete the set. Is that simpler than enumerating the things that define the set? No.

Maybe I should find the Neil Tyson video where he lays out this as the way he'd prefer to solve the whole issue. He probably sells it better than I do.

"[you have to define] “Sun”. And “orbit”. And “round”. And the definition of “set” And…And…And… Or just say “planet”."

You're kidding, right? To define planet you need to define all those things, and "clearing the neighborhood" besides!

Unless you're seriously suggesting talking about the "planets" are WITHOUT defining any of those things? So someone would know that there is a planet called "Mars", but not even the most basic of facts about it, the very facts that define it as a planet -- like orbiting the sun?!

If you give a name to a set of properties then you have to define those properties or the name is meaningless. And then you have to define the name in terms of those properties. So there's always one more definition this way.

Not that I care about that metric. Not sure why you would either.

* Which is appropriate when the degree of roundness implied by hydrostatic equilibrium is far greater than that of a queue ball, forget about a baseball. Just like "cleared the neighborhood" is perfectly clear when talking about planets due to the orders of magnitude difference between them and the orbits of any non-planet.

Neptune was also discovered by gravitational influence and only then visually observed.

The problem IMO is once you get to Pluto and Kuiper Belt, there comes an issue from where do "wobbles" come from? It can be a single object messing with i.e. Pluto's orbit, or can be many. The fact Pluto got demoted is precisely because larger objects were found. As for a bigger planet. Well, "planet x" could be out there. I personally don't believe it. But it's possible to have a very big orbital period.. say more than 500 years. Last time it was "around" we didn't have telescopes. Like I said, I don't think it likely, but its possible.

Yeah, it was a stroke of good luck that Neptune and Uranus happened to be in the parts of their respective orbits where we could see Uranus speed up and slow down.

Had that not been the case, it might have been another

80 years before we discovered Neptune, if nobody discovered it through serendipity.

* 80 years? I don't think that's right. There's a question -- how long between Neptune/Uranus interactions?

Uranus and Neptune are in an approximate 1:2 resonance every time Neptune orbits the Sun (

165 years) means Uranus will make two complete orbits (

88 years each). The combination of these two things means that Uranus passes Neptune in its orbit once every 165 years: once around 1830, recently just prior to the turn of the millenium, and will do so next in the far future around 2165 or so.

You can see for yourself by using an orrery app this one is my favorite: http://www.dynamicdiagrams.com/wp-content/uploads/2011/04/orrery_2011_b…

There is NO single "modern understanding, "current definition," or "classification in use for the term planet. There IS an ongoing debate between dynamicists, who believe a spherical celestial object that is not a star must be the dominant thing in its orbit to be a planet, and geophysicists, who believe that a spherical celestial object that is not a star is a planet, whether or not it dominates its orbit. According to the equally legitimate second definition, some planets gravitationally dominate their orbits (terrestrials and jovians) while other planets do not (dwarf planets). This does not make dwarf planets not planets at all. According to this definition, Eris is a planet Pluto is a planet, and even Sedna might be a planet, in which case it rather than Eris would be the solar system's furthest planet. NO objects larger than Pluto have been found in the Kuiper Belt so far. Eris was initially thought to be bigger than Pluto, but in November 2010 was found to be smaller than originally thought and actually marginally smaller than Pluto though more massive.

The notion that we cannot have too many planets because that would mean "a ridiculously large set of names" that no one could memorize has no scientific merit whatsoever. It is akin to saying there cannot be billions of stars or billions of galaxies or that Jupiter cannot have 67 moons because no one can memorize so many names. Our solar system has whatever number of planets it has, and it makes no sense to try to artificially limit that number for the sake of convenience.

Spherical moons have many of the same properties and characteristics of planets, and some may even harbor subsurface oceans. The only difference between them and classical planets is that they orbit other planets instead of orbiting stars directly.

An object does not even have to orbit a star to be a planet. Several rogue planets have been discovered that orbit no star but just free float in space. Obviously, the can't "clear their orbits" if they don't have any orbits!

What makes the most sense is keeping the term planet broad to encompass any non-self-luminous spheroidal body orbiting a star or free floating in space. We can then use subcategories to distinguish the many different types of planets: terrestrials, gas giants, ice giants, dwarf planets, hot Jupiters, super Earths, satellite planets, rogue planets, etc.

Laurel: "There is NO single 'modern understanding', 'current definition,'"

Actually, there is precisely one current definition as defined by an organization representing enough astronomers to count as "official". Doesn't mean you have to like, or even use, that definition, but that's what it is. Given that there didn't used to be any such definition, then it's fair to consider whether dynamics should be part of the definition or not.

All I'll say on that is: The original meaning of planet was based *entirely* on dynamics, and in modern times the issue has come up before and was decided in favor of dynamics and orbital dominance when Ceres was first named a planet, then "demoted" just like Pluto when it was discovered to be only a fraction of the total mass in its orbit. So I think the current definition is more consistent with the historical usage.

But if you want "planet" to mean "round" and another name for large moon is "satellite planet", well, fine. I don't care about the word "planet" so much. It's just nomenclature. The objects themselves don't change.

"The notion that we cannot have too many planets because that would mean 'a ridiculously large set of names' that no one could memorize has no scientific merit whatsoever."

That's not what I said. I was talking about giving names to subsets of properties. Obviously each individual object is going to have a name regardless of whether it is a planet or not.

But your objection to what you thought I said is premised on the idea that the planets are the only names we'd care about and have to remember. Which is basically my point, that the word "planet" itself has cultural and historical significance that goes far beyond any scientific merit. Which is zero -- the name "planet" and the set of objects that fall in it is irrelevant.

After all, if you make "planet" not depend on gravitational dominance, the set of non-stellar objects in our solar system which are gravitationally dominant still has 8 members. And every other property stays the same, too. Does Vesta or Pluto not falling in the category of "planet" in any way change the scientific interest of these objects? No, and that's why we had/have missions to study these objects. What they are, and what we hope to learn from them, has nothing at all to do with what we *call* them.

So my point is: Why specify every single combination of properties -- which only considering roughly-binary properties leads to 3^n categories (each could be true, false, or don't care)? Why specify only some "special" subset of properties, which necessarily means failing to capture distinctions that may be important? You'll just end up adding adjectives and essentially doing what I propose when you want to distinguish between hot super earths and cold super earths, rogue ice giants and rogue gas giants. Are those going to get special names, too? Or maybe this style of nomenclature is ineffective for properly representing the breadth of objects out there?

" Does Vesta or Pluto not falling in the category of “planet” in any way change the scientific interest of these objects?"

However, Pluto was discovered by an American Astronomer, but I'm sure there's nothing relevant in that 8-)

"Yes, to be precise I’d say “hydrostatic equilibrium”"

"“[you have to define] “Sun”. And “orbit”. And “round”. And the definition of “set” And…And…And… Or just say “planet”.”

YOU DEFINED PLANET as "round object orbiting the sun".

Define orbit. Our moon goes round the sun. We pull it there.

Define Sun. Jupiter is near-stellar, producing a notable fraction of the energy it receives.

You didn't think this through and rather than consider it decided merely to go hogwild and ignore any possible thinking on the subject.

And then go ignoramus and try to imply that you were being sane in a mad world by going "Are you serious?"

Extremely condescending and moronic and lacking in any sort of rationality.

And, indeed a trolling comment.

Your idea was bad and you should feel bad. Get over it.

"YOU DEFINED PLANET as 'round object orbiting the sun'"

Yes, and obviously all the terms needed to define planet must themselves be defined. They all also have reasonable definitions -- ones that are already understood in context.

YOU said that instead of going through this necessary exercise for defining a word: "Or just say 'planet'."

Which, in the case where "planet" has a definition, necessarily means also defining the terms used to define planet, making that statement idiotic because it's acting like it's an alternative while it's actually not.

OR you avoid having to define the terms that define planet by not defining the word planet so it doesn't mean anything, which would be even more stupid, just absolutely idiotic.

So you either have the same "problem", or avoid the "problem" by creating a real (stupid) problem. Good job!

"You didn’t think this through"

Once again you accuse others of what you yourself are guilty of, exacerbated by the accusation itself. It's amazing how often you fail to connect two thoughts together and thus fail to understand a simple point. Even more weird is how it consistently happens when the point being made undermines your own.

"Your idea was bad and you should feel bad. Get over it."

Your attempt to show this was stupid and you should feel stupid. You have to define 'Sun' and 'orbit' in any sane discussion of objects in the solar system. It is not in any way a reasonable objection.

Come back when you have a real point. Try thinking about it, first, though.

"However, Pluto was discovered by an American Astronomer, but I’m sure there’s nothing relevant in that"

Yep, discovered by an American, and honored by Disney in cartoon dog form.

But yeah, clearly irrelevant trivia. =D

"YOU said that instead of going through this necessary exercise for defining a word: “Or just say ‘planet’.”"

It's a hell of a lot easier to say than "a round object that orbits the sun that is in the list of <. >, isn't it.

"Planet"
vs
"a round object that orbits the sun that is in the list of <. >"

The point is the the first one is one people use. The second one is not what astronomers use, but similar, however they STILL have to talk to non-astronomers. Where they'll use "Planet".

Your "alternative" throws out planet and then goes even worse than the current definition and ensures that nobody will bother to change.

They'll STILL call it planet.

The astronomers have a definition. It ISN'T yours.

But despite that definition, "Planet" will remain used. If anyone needs to know what it means, they can look it up.

And for teaching kids, "Planet" will mean
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune

"A list of things that are planets".

It will not tell you how to decide whether Planet X is a planet if ever it's found. Neither will yours.

The AU version of the definition of the planet WILL.

So your alternative throws that baby out and then decides to put dry ice in instead of water.

And call it an improvement.

I always thought Pluto was Goofy.

"The astronomers have a definition. It ISN’T yours."

Wait, what? As I've been saying from my first post I think gravitational dominance is an important property for defining planet. I AM using the astronomer's definition for "planet" and never suggested otherwise. I said "yes" when you gave that example in your one-previous post because I thought it was just an example, not the foundation of half your issues!

Also, where did that "in the list of <>" nonsense come in? Arbitrary lists are not the kind of property I'm talking about.

Now lets talk about the other half of your issues, which are from not defining planet at all.

"however they STILL have to talk to non-astronomers."

Yes, I know. And why do non-astronomers care that astronomers use the word "planet"? Because of that historical and cultural significance I keep talking about. Keeeep talking about. That's the only reason. It's the only reason we teach kids specifically about this particular set of objects, and not just interesting objects in general -- though even when I was first introduced to them, it included that they were big round objects in space that went in circles around the sun, as opposed to the asteroid belt which was a bunch of smaller objects that went around the sun. Do we really teach kids "this is the list of planets" and when they ask "what's a planet?" teacher says "it's the things in this list"? Sounds like nonsense to me.

Anyway, scientifically, there's no reason to care about what objects qualify as "planets". That name has no inherent significance. The set of properties it is defined as may or may not be significant to any particular slice through the population of solar system objects someone is interested in. That's why I said "ideally".

Trust me, as someone who works with x86 on a regular basis, I know the difference between what would be "ideal", and what is "practically necessary" because of history.

So, accepting that the word "planet" will remain in our vocabulary and that therefore a definition most in keeping with its past unofficial use is appropriate, do you have any objection to a hypothetical world where the word "planet" isn't carrying along that baggage, and instead we only worry about objects with a set of properties we're interested in?

Nothing stops you from assigning a name to your favorite set of properties. The point is that there'd be no significance other than the properties it's defined as, which would also be the most clear and precise way to communicate the concept. So no fights over definitions that ultimately don't matter.

"It will not tell you how to decide whether Planet X is a planet if ever it’s found. Neither will yours."

Now that's just silly. Of course "my" definition (reading here the one you imagined I was proposing) would tell you how to decide. Just like the IAU's does. Any definition that consists of having a set of properties allows you to know which objects fall under it by which objects feature that set of properties. Duh.

Of course if you instead meant the case where I'm not defining "planet" at all, then duh it won't tell you what's a planet, because the whole point is it wouldn't matter.

"Wait, what? As I’ve been saying from my first post I think gravitational dominance is an important property for defining planet"

The defence of your "idea" isn't made any more valid by saying "I just listed the names of the known planets the same as the official one!".

Your idea is pointless, a better one has already been done by experts, and nobody other than you thinks throwing away the word "planet" is a good idea.

Of course, Pluto and Ceres are planets. The IAU Executive Committee decided to ram a rancid resolution down the throats of the 400 or so members who attended the last day of the Prague General Assembly on St. Bart's Day 2006. Another massacre was committed, just ask Mike Brown who thinks he killed Pluto. The IAU's defintion of a planet is horrid, and many planetary scientists have rightly rejected it. If you want to kowtow to such horridness, they is your choice. I choose not to kowtow to an organization that whose Executive Committee has sent impish emails to me, full of arrogance and, I must add, I know one member who said they were pressured to vote to demote Pluto at the threat of the destruction of their career as an astronomer. If that does not make you think the definition is flawed with subjective and possibly political considerations, then you are a lackey. Alexis de Tocqueville once said the worst insult you can hurl at someone is to say that they have "the soul of a lackey." I suggest you reconsider your relationship to the IAU.

If Earth was as far out as Pluto, it wouldn't be a planet, either. As Dr. Alan Stern said (paraphrasing), that would be absurb for planets are based on Earth.

Good article Ethan -cheers.

Although Triton is more an exiled ex-King than a current one.

As for the big planet Pluto debate, I think Dwarf Planets are as much still planets as dwarf stars are dwarf stars are still stars.

(And like with stars dwarfs are more common than giants.)

The IAU definition is controversial and many , even professional astronomers disagree with it for a wide range of reasons.

The IAU got it wrong in many ways because for starters they automatically excluded all planets outside or solar system and let's face it this breaches the whole Copernican principle and is totally unjustifiable.

It also by definition (literally!) excludes orphan planets which formed far from any star or were ejected from their suns early or later in their history.

As #28 Mark Wrathell points out the IAU definition means that Earth would stop being a planet - and Pluto would become one - if their orbits were swapped. Clearly that situation is nonsense and a planet is a planet wherever it's found.

Furthermore just because there's a lot of something in a relatively small area doesn't mean it stops being what it is. Just because you have a zone with a lot of a certain type of planets (e.g. Pluto, Eris, and the other ice dwarfs) deosn't make them not planets for the same reason that having a zone full of certain types of plant eg. a grassland means that grass isn't a plant because its so common there.

The IAU definition is clearly fatally flawed and will have to be changed (itis already effectively ignored every time we talk of planets around other stars,etc ..) and the sooner this happens the better.

The alternative, new definition I'd suggest? Well it should be simple, easily determined and clear. I'd say an object is considered a planet if it meets three basic criteria :

1) Never self-luminous via shining by natural nuclear fusion thus not a star.

2) Gravitationally rounded by its own mass and thus not an asteroid or comet nucleus or other small body.

3) Not directly orbiting another planet and thus not a moon.
(note there are almost certainly cases where two worlds mutually orbit each other and in these cases both worlds would count as a double planet. This may be the case for Pluto and Charon.)

So Pluto meets these criteria, so does Eris, so does Earth and Jupiter and so on.

Yes, this means there's a lot more than just nine planets in our solar system - so what? It makes sense to consider it divided into three zones -the rocky planets one (Mercury to Mars), the gas planets zone (Jupiter to Neptune) and the ice planets zone. (Pluto to Sedna.)

I think this best reflects astronomical reality and is the way to go -and I also think the current temporary definition will be one that future children look back on with baffled astonishment that the IAU could embarrass itself so badly and come up with something so ridiculous.

After all, Pluto has all the features of a planet as we usually consider it - moons (more than all the inner worlds put together!), internal differentiation, an atmosphere even weather - methane snow and perhaps rings as well. If its not a planet then nothing is! -)

"The IAU definition is controversial "

The only reason for it is something other than it being the one planet discovered by an American.

The IAU decision is no more constroversial than the re-definition of the inch to be exactly 25.4mm.

@ ^ Wow : "Not controversial" - seriously?

Nonsense. If it wasn't controversial we wouldn't still be talking about it! It is very much a controversial issue and one that argued about by a whole lot of people - including many from outside the USA like me (I'm an Aussie.) and disputed by serious professional astronomers as wellas those in the public.

For instance, Alan Stern among many other experts who were excluded from the last minute IAU vote* has flatly stated that the IAU's decree was :

“ . idiotic. I have nothing but ridicule for this decision.” (Alan Stern, P.28, ‘Astronomy Now’, October, 2006.)

After the debate a huge number of objections were raised by astronomers of all levels and the general public too. Many modern astronomers still reject the IAU's definition with some planetary astronomers going as far as including Vesta as the smallest terrestrial planet. (Read in an article on that in an astronomy magazine which was publsihed a while ago - forgotten exact name & source but can find later if you want.)

But, really think of it this way, the main "logical" objection that Pluto-bashers seem to have against counting Pluto is that it is that there are other small similar ice dwarf planets such as Eris, Haumea, Sedna etc .. around it.

Or to put it algebraically, X stops being X when surrounded by fellow Xs.

If this "logic" were followed then people would stop being people as soon as they joined together in a crowd! -)

The anti-Pluto "logic" really is that silly and I hope that example shows why the IAU got their definition terribly wrong.

* The lack of democracy of the Pluto / Planet definition vote is clear by the fact that of the 10,000 IAU members only 2,500 attended the Prague meeting and of those 2,500 only the merest handful – just 424 actually got to vote making therefore a very unrepresentative decision. Notably a number of key Pluto & outer solar system experts incl. Stern weren't present and thus unable to put an opposing case at that occasion.

Minor correction to my #32 :

the main “logical” objection that Pluto-bashers seem to have against counting Pluto is that it is that there are other small similar ice dwarf planets such as Eris, Haumea, Sedna etc .. around it.

By "around" I meant "nearby" - for a certain value of nearby! These large ice dwarf planets (Pluto, Eris, Makemake, etc ..) are still spread very far apart in space - much more so indeed than the inner planets.

(There are also a few typos and grammar stuff ups but I hope you forgive me and get the gist anyhow.)

Which leads me to suggest the following thought experiment - if the inner solar system was more crowded with planets like Earth and Venus, perhaps in orbits that cross each others* do you really think that would stop them being counted as proper planets? Ditto, what if Jupiter had another two or three or five or ten similar gas giants crossing its orbit or in a similar zone in perhaps a hypothetical extra gas rich and chaotic alien planetary system? How many nearby worlds and how close before a planet of whatever category - gas giant, rock dwarf or ice dwarf - ceases to count as a planet?

I think the answer is that however many planets (whether Earth-like, Pluto-like or Jupiter-like) there are nearby - and don't forget we're starting to find some pretty crowded exoplanetary systems and more no doubt are out there - a planet is still a planet.

If anyone disagrees then please explain why and what you think we should call such planets in such circumstances then.

I'd also like to note this article by Ken Croswell :

providing his alternative definition and argument because I think its well worth reading and contemplating in this context.

Plus Ken Croswell asks a couple of great thought-provoking questions on his site which I'd also like to link here if this is okay :

Hope it is and apologies and please let me know if it's not Ethan Siegel.

(Not sure how many links I can post at once without triggering moderation or spam filter hence this separate comment.)

PS. Click on the articles and scroll down to find the first and also fascinating Pluto question there. If you want to naturally but I'd certainly recommend it!

"By “around” I meant “nearby” – for a certain value of nearby! "

Well if there were no value for "nearby" the word would have no meaning, would it.

You're insisting on one of the planks of denial here (an impossible standard) because you DO NOT WANT Pluto excluded.

If, as you claim, you have no problem with having dwarf planet == planet, then why the contortions of logic to insist it must be treated differently.

"@ ^ Wow : “Not controversial” – seriously?"

* (From #33) "if the inner solar system was more crowded with planets like Earth and Venus, perhaps in orbits that cross each others.. "

This was, in fact, almost certainly was the case early on in our solar system's history hence Earth's Moon's formation among other things and could become the case again later on in solar systems evolution as well - see :

Suggesting that Mercury could eventually end up colliding with Earth due to gravitational perturbances accumulating and causing a chain reaction of sorts over aeons.

"This was, in fact, almost certainly was the case early on in our solar system’s history"

And before the sun coalesced, there was no earth to reference "wanderers" to.

Empty, Stevo. Completely empty.

Did you know that there was no language of humans to name things in those dim and distant days?

You keep making assertions without logical argument or examples.

Why exactly may I ask do you think Pluto isn't a planet?

Where exactly have I erred in logic or fact in your view?

Could you please answer the hypothetical questions I asked in comment 33?

Also please tell me if you think that having enough of also Xs around sudden somehow makes X into not-X? (E.g. if enough people gather into a crowd do they stop being people?) Because that's the main reason I see for people asserting that Pluto isn't a planet - and you should by now see why that claim is illogical and even ridiculous.

@ 38. Wow : "Did you know that there was no language of humans to name things in those dim and distant days?"

So by that "logic" of yours there all of palaeontology is out of business because we can't name dinosaurs and trilobites and all these other things that still existed long before we did - let alone have cosmologists discussing the Big Bang!?

There's language we use now and that's why we an discuss the past on whatever scale we choose.

PS. @Wow : Did you read the links I've provided for you and try answering Croswell's Pluto questions? How did you do and what do you think of them?

StevoR says, "It makes sense to consider it divided into three zones -the rocky planets one (Mercury to Mars), the gas planets zone (Jupiter to Neptune) and the ice planets zone. (Pluto to Sedna.)"

I guess that rules out Ceres as a planet.

And hot Jupiters are ruled out from being planets.

@ ^ Wow : No. Because I was talking here only about the structure of our solar system. Other planetary systems can and do have other ways of being organised including Hot Jupiters close in.

@42. Richard S. : No, I'd count Ceres as among the inner rock dwarfs.

Stevo, you're not listening.

Your new "explanation" is now that you were going to define planets as "only those things orbiting OUR sun". Well, that makes your new definition even MORE worthless.

PS where the effing eff do you get the new "rocky dwarf" shit from?

How about calling Pluto a "rocky dwarf" too?

Oh, no, that won't do because Pluto has to be a planet, right?

@^ & 45. Wow. No. That's not what I'm saying at all. The exact opposite.

It is the current IAU definition that defines "planet" in that way as I think I've already noted. Read a bit more closely, mate.

As where I get rock dwarf from, hmm. do the words "gas giant" ring any bells for you? Plus yellow dwarf, blue dwarf, white dwarf, red dwarf etc .. -)

Makes sense to call relatively small rocky planets "rock dwarfs" following that precedent and I'm pretty sure I'm not the first to come up with that term.

There's probably also a case for calling some rocky sure Earth's "rock giants" and some other so-called super-Earth's that may be more like mini-Neptune's gas dwarfs in fact I believe Sara Seager suggested that at one stage.

Seeing as I've answered all your points, you care to reciprocate and finally answer my earlier questions in this thread in comments 33, 39, & 41?

(Or you just trolling bro'? Kinda looks that way to me.)

"It is the current IAU definition that defines “planet” in that way as I think I’ve already noted. "

So when did you change from:

"The IAU definition is controversial and many , even professional astronomers disagree with it for a wide range of reasons."

To an "I agree with the IAU's definition"?

"As where I get rock dwarf from, hmm. do the words “gas giant” ring any bells for you?"

Yes. Gas Giant does ring a bell. It's been used for decades. However, care to elaborate how "Gas Giant" defines "rock dwarf"?

@Wow #46: Sometimes its hard to tell when you are being rhetorically dense, vs. whether you really are as obtuse as you appear.

Let's play a little game. Describe a non-luminous macroscopic astrophysical object. Give it a two word label of the form . The first adjectival noun may be chosen from the list . The second adjectival noun may be chosen from the list .

Notice that the construction and the form of each label is the same. Anyone (else) with a reasonable grasp of English and an ability to recognize patterns would have figured that out for themselves, given StevoR's writing.

Yes, I am aware that cromulence can indeed become a legitimate word, Mike.

And I likewise also understand that "rocky dwarf" means "a rocky small planet" in this context.

Still, thanks for telling me shit I know. Care to answer the queries I *did* have? You know, the ones I actually wrote, rather than ones you think I missed out?

Mike, if you're looking for questions not asked, why not "Why is it you think that all solar systems must have inner rocky planets, then gas giants then ice?".

Especially odd to consider when I mentioned Hot Jupiters (which would be in the "rocky planets" area) but summarily pooh-pooh'd by Stevo.

Did your gimlet stare not go that far?

"Trust me, as someone who works with x86 on a regular basis, I know the difference between what would be “ideal”, and what is 'practically necessary' because of history."

Haha. That's a good one. I'm going to remember it.

"So when did you change from: “The IAU definition is controversial and many , even professional astronomers disagree with it for a wide range of reasons.”To an “I agree with the IAU’s definition”?

I didn't. I totally disagree with the IAU definition for teh reasons I listed in comment #30 including :

" .. The IAU got it wrong in many ways because, for starters, they automatically excluded all planets outside or solar system and let’s face it this breaches the whole Copernican principle and is totally unjustifiable. It also by definition (literally!) excludes orphan planets which formed far from any star or were ejected from their suns early or later in their history.

Yeesh, that was only like the very first point I actually wrote immediately after the quote you gave there! How did you miss that?

"Yes. Gas Giant does ring a bell. It’s been used for decades. However, care to elaborate how “Gas Giant” defines “rock dwarf”?"

By contrast. You have gigantic gas giant planets and then you have the rocky worlds that are dwarfed in comparison just like you have blue giant stars that dwarf yellow dwarf stars such as our Sun and this has been the conventional astronomical terminology for a long time now so keeping to that seems eminently reasonable.

@50. Wow : "Care to answer the queries I *did* have? You know, the ones I actually wrote, rather than ones you think I missed out?"

What, you mean just like how you've rather hypocritically failed to answer every question I've asked *you* Wow?

How about you answer the following questions that have already put to you & are being asked thrice now :

1) Why do you think Pluto is NOT a planet precisely?

2) Did you read the links I’ve provided for you and try answering Croswell’s Pluto questions? How did you do and what do you think of them?

3) Do you you think that having enough things that are X together suddenly somehow makes X into not-X? (E.g. if enough people gather into a crowd do they stop being people?)

@51. Wow : "I mentioned Hot Jupiters (which would be in the “rocky planets” area) but summarily pooh-pooh’d by Stevo."

Wow, you sure do get get it wrong don't you? Your lack of comprehension of what I've clearly stated amazes me. I've got nothing against Hot Jupiters and have actually used them to support my case here.

Planets come in a whole lot of varieties covering a vast range of sizes and orbits such as Hot Jupiters, rock dwarfs, gas dwarfs, gas giants, ice giants, ice dwarfs etc .. and *all* of these are still planets. Whether they are Hot Jupiters or ice dwarfs or whatever. The diversity in planets size, orbits, etc .. is like the diversity in animals, plants and stars. Ie. very broad indeed. ( Analogous to the differences in size between Blue Whales versus Bed Bugs, Sequoia sempervirens (Giant Redwoods) to algae, Betelgeuse to the Crab Nebula Pulsar.)

"Your lack of comprehension of what I’ve clearly stated amazes me. I’ve got nothing against Hot Jupiters "

Irony. Definiton. Claiming someone else has clearly not comprehended what was said and then does precisely that in their following sentence.

You see, numbnuts, the problem here isn't that you made up the name rocky planets, nor that you don't like Hot Jupiters, but that the presence of Hot Jupiters in what you have "defined" planets to be: the rocky planets near the sun, gas giants further out and ice planets in the distance, means that there can be no planets unless they are icy ones after the Hot Jupiter.

You pooh pooh'd there was any problem with your assinine "definition" crafted solely to keep Pluto in as a planet (moronically, by merely saying "it will be this list" which apparently would be updated if any new ones were found, but cannot be updated for Ceres to be added nor updated to remove Pluto. By edict alone).

Is this getting through that thick skull now?

Try not to go troll on us, okay? Calling people "numbnuts" is contemptible given the circumstances. Someone thinks Pluto and the other dwarf planets are planets and you get your panties in a bunch and start name-calling? Really? Are you a lackey of Mike Brown or Mike Brown himself perhaps?

The IAU ramrodded that resolution down the throats of the remaining attendees of the 2006 GA on the last day of it, without proper vetting or notice, and one member has stated publically that he was threatened with the destruction of his astronomical career were he to side with Pluto. Does that not goad your conscience?

There should be three sub-classes of planets. Jovian, terrestrial, and dwarf. Sedna may not be a dwarf, as far as I know. By the way, the name is Mike, not Mark.

Try to be succinct, people. Be kind to those who want to be in this discussion. Everyone has an opinion. Share it, but if you want to write a novel, send those to a literary agent.

Well, Mike, being deliberately obtuse, ignoring what's said to say something else, and assuming incompetence in your rephrasing is also contemptible.

I guess contempt can be found all over the place, eh?

Pluto isn't a planet because any definition that doesn't special plead Pluto in includes planets that make the numbers ridiculous or excludes Pluto.

"rocky planets" aren't going to be a definition of planet any more than "Chimpanzee" is going to be a definition of a simian.

"The IAU ramrodded that resolution down the throats of the remaining attendees of the 2006 GA"

Like the Senate "ramrodded a resolution" down the throats of the Republicans?

When those remaining attendees are going to dig their heels in because their sense of national pride is more important than resolving a classification problem, then of course it's going to be "on the last day".

By the way, using that language is contemptible. Just letting you know.

And lastly, Steveo's "definition" was no improvement over it, becoming merely a list of "things we've named that are the ones I was taught in school so I won't be wrong".

"There should be three sub-classes of planets. Jovian, terrestrial, and dwarf."

However, the definition of planet needs to be made for you to make SUBCLASSES of *PLANETS*.

Which was why "rocky planets" was no damn definition of planet at all.

That you are extremely partisan is entirely why you've come over all butthurt on this. And your partisanship is evident by you choice of attribution of malice to the IAU when a minority wanted to find some special pleading to keep Pluto, discovered by a USian scientist, a planet.

And everyone has an arse. This does not make them speak truth.

There is not one definition of planet that counts as official just because 424 astronomers, most of whom are not even planetary scientists, say there is. SOME astronomers use this definition, but it is completely inaccurate to generalize and say that all or even most use this definition. There are several planet definitions in use by astronomers, and none has more merit than the other--meaning this is the subject of ongoing debate. In science, something does not become "the truth" just because a so-called authoritative body says it is. The IAU definition remains controversial seven years later because it was poorly and hastily constructed and does not take into account alternative views and new discoveries in planetary science. The fact that the IAU leadership refuses to even revisit this issue indicates the group is more interested in safeguarding its perceived "authority" than in safeguarding the science of astronomy. The idea of dictating a definition once for all eternity and never again revisiting the issue is the action of a church, not of a scientific organization.

"Pluto isn’t a planet because any definition that doesn’t special plead Pluto in includes planets that make the numbers ridiculous or excludes Pluto."

This statement is ridiculous. A geophysical planet definition in which any non-self-luminous spheroidal body, either orbiting a star or free floating in space (to include rogue planets), makes perfect scientific sense. In contrast, the notion of "making the numbers ridiculous' makes absolutely no sense whatsoever. The universe has a "ridiculously" large number of galaxies, stars, and yes, planets. Get used to it.

A good recommendation by some astronomers is the creation of a system to classify planets similar to the Herzsprung-Russell Diagram used for stars. Such a system could incorporate the many subclasses of planets based on age, location, composition, etc. Planet is a broad category the subcategories are what distinguish the many types of planets.

It is actually more sensible to call Pluto a rocky dwarf than an icy dwarf since Pluto is estimated to be about 70 percent rock. Eris, being 23 percent more massive, is likely even more rocky. Ceres appears to be a small terrestrial planet that might even have a subsurface ocean.

The discovery of rogue planets illustrates that even a "requirement" that an object orbit a star to be a planet is problematic. Rogue planets are not self-luminous, so they are not stars. They cannot clear their orbits because they don't have any orbits. Granted, we don't know much about their composition yet, but if they are not planets, what then are they?

First of all, thank you for your concern over the comfort of my posterior. That is very touching. It is fine, I will have you know.

What of my comments do you find obtuse? I saw a video of the rancid resolution being ramrodded. Pluto huggers were cut off in mid-sentence during that session. Ms. Bell reluctantly gave the mic to a Pluto hugger and then crossed her arms contemptuously as he spoke. Her body language and demeanor were atrocious and shameful. So why can't you give your real name? Do you like being a troll and calling people numbnuts that much that you are afraid to reveal your real name? C'mon, dude, get real.

"Ms. Bell reluctantly gave the mic to a Pluto hugger and then crossed her arms contemptuously as he spoke"

Just because someone is being an ignorant arse doesn't mean you have to pretend they aren't , Mike.

Pluto hugging was just Team America being butthurt.

@ ^ Wow : I'ma Pluto hugger and I'm an Australian, of English-Aussie background and no USA family connection. (Visited there once for a week that was all.)

It bothers me because its such a clearly wrong definition and so inconsistent with the rest of astronomy.

Needless personal abuse - yep , you're a troll alright, not that I or anyone else reading would have had much doubt of that by now.

". the problem here isn’t that you made up the name rocky planets,"

I didn't "make up" the name just used an already common terminology.

. nor that you don’t like Hot Jupiters.

I like 'em just fine. Can't say I'd want to live on one but they are remarkable planets in their own rights.

"..but that the presence of Hot Jupiters in what you have “defined” planets to be: the rocky planets near the sun, gas giants further out and ice planets in the distance, means that there can be no planets unless they are icy ones after the Hot Jupiter.

Bzzzt. Wrong. I defined planet back in my first comment here ( # 30) as :

1) Never self-luminous via shining by natural nuclear fusion thus not a star.

2) Gravitationally rounded by its own mass and thus not an asteroid or comet nucleus or other small body.

3) Not directly orbiting another planet and thus not a moon.

The description of the specific arrangement in our solar system was a seperate thing entirely and not part of that definition.

But I guess you are probably already aware of this and just trolling to stir things up. Not mad bro' - your'e too obvious and poor quality a troll for that. -)

@57. Laurel Kornfeld : Well said and seconded by me.

"A good recommendation by some astronomers is the creation of a system to classify planets similar to the Herzsprung-Russell Diagram used for stars. Such a system could incorporate the many subclasses of planets based on age, location, composition, etc. Planet is a broad category the subcategories are what distinguish the many types of planets."

Absolutely right. We already know and have a whole menageries of star types from blue supergiants which are millions of times brighter than our Sun and so large their surfaces would extend out to Mars if placed in our solar system at one extreme to the numerous faint red dwarfs that shine with hundredths of a solar luminosity and are only the radius of Jupiter in size.

So too do we already know of gas giant planets bordering on brown dwarf star territory in mass and size down to
ice dwarfs like Sedna about a quarter of Pluto's size for planets. Astronomy contains a really diverse range of objects and "planet" has to be a really broad and inclusive category just like "star" because of that.

"It is actually more sensible to call Pluto a rocky dwarf than an icy dwarf since Pluto is estimated to be about 70 percent rock. Eris, being 23 percent more massive, is likely even more rocky."

Another good point there. The ice dwarfs, at least many of them are more rock than ice. I guess I think ice more because of the distance and chill in that far outer realm of our solar system.

" The discovery of rogue planets illustrates that even a “requirement” that an object orbit a star to be a planet is problematic. Rogue planets are not self-luminous, so they are not stars. They cannot clear their orbits because they don’t have any orbits. Granted, we don’t know much about their composition yet, but if they are not planets, what then are they?"

Also if you did have a rogue planet on collision course with Earth (or any other planet) - then Earth (or whichever other planet) would then automatically stop being a planet just because its orbit therefore wasn't "clear"* showing again how silly the IAU definition really is.

* Thinking of which we already have asteroids and comets that cross all planetary orbits s that no orbit is *ever* really "clear" anyhow.

PS. Wow. I notice you still haven't answered any of my questions as asked politely a few times most recently at #47.

Oh & you seem to be prejudiced against Americans "Wow" -did you realise that you're being anti-American on a blog written by an American? A bit churlish as well as bigoted of you I think.

Well, Steve, lets look at the questions in #47.

> As where I get rock dwarf from, hmm. do the words “gas giant” ring any bells for you?

Answered. My query about "What the fuck does that have to do with it" went unanswered. Responded? Yes. Answered? No.

"Seeing as I’ve answered all your points, you care to reciprocate and finally answer my earlier questions in this thread in comments 33, 39, & 41? "

Seeing as you didn't answer them.

But that seems to be the only two questions.

One answered and the other a "russian doll" one and insisted on being answered because you confused a reply with an answer.

"I’ma Pluto hugger and I’m an Australian"

Whoop de doo. Nice for you. What does that do? Nowt.

"It bothers me because its such a clearly wrong definition"

Yes, repetition of a claim with zero supporting evidence is not proof of the repeated claims' veracity.

In short, YOU'RE STILL WRONG.

"and so inconsistent with the rest of astronomy. "

"Needless personal abuse – yep , you’re a troll alright,"

Needlessness is irrelevant. It was DESERVED personal abuse, numbnuts. Don't like it? Don't act nuts. Simples.

"I didn’t “make up” the name just used an already common terminology."

Yup, you never read #54, '56, did you. Even though you quoted it:

“…the problem here isn’t that you made up the name rocky planets,”

If the problem wasn't you making up the term (which I never claimed you made the fucking term up you tiresome retard), then why the FUCK are you whining "I never made the term up?"

IF THAT ISN'T THE PROBLEM claiming you never made it up DOES NOT RESPOND TO THE PROBLEM YOU RETARDED SHITHEAD!

"Bzzzt. Wrong. I defined planet back in my first comment here ( # 30) as"

You re-defined it later. Shall I quote what you said since you deliberately ignore what you spout when you like it?

> It makes sense to consider it divided into three zones -the rocky planets one (Mercury to Mars), the gas planets zone (Jupiter to Neptune) and the ice planets zone. (Pluto to Sedna.)

You won't see it because you're too busy going "I WANNA PLUTO! I WANNA PLUTO! GIMME A PLUTO! YOU STOLE MY PLUTO. "

"Absolutely right. We already know and have a whole menageries of star types from blue supergiants"

Moron, he's not talking about different stars.

He's talking about the different organisations of planets in a solar system.

Ours is not the only organisation of planets possible.

Which is why your "definition" SUCKS DONKEY BALLS.

It seems rather pointless to continue this charade of an reasoned argument between two points of view, given your name-calling and lack of cogency, but I will say a few more things to wrap this up on my end. Many well-respected planetary scientists like Alan Stern and David Rabinowitz signed a petition protesting the demotion of Pluto. You act as though only "morons" and "numbnuts" hug Pluto.

You are right that Ms. Bell has the right to cross her arms and show her hand regarding her position on Pluto. It was unprofessional, of course, as was her cutting off other Pluto huggers in mid-sentence and ramrodding the rancid resolution down the throats of the IAU's membership, but she has the right to her opinion, as do you.

I am not going to go into a point by point rebuttal with you as my time is valuable and you seem to have nothing better to do than cast aspersions on people behind a fake name.

If this is the best that you can do, you are not much of an astronomer or whatever it is you are.

Even if I'm rude, that doesn't make your asinine assertions, nor Steve's, right.

If that's all the proof you have against, me, try again.

Yeah, the complaint of any asshat that doesn't get their way and are overruled.

"WAAAH I WANNA PLUTO. ". Rancid.

Yes, rancidly ramrodded rancid resolution. What makes my assertions assine, the fact that you like to swear? I can swear, too, but do not want to sink to your level, Wow. You are ignoring my points, bro. I guess it is okay for you to ignore points,huh?

"What makes my assertions assine"

The fact it's completey whiney made up bullshit?

Mike, when a vote is made and the vote doesn't give you the answer you want for no damn reason at all, losing the vote is called "Democratic process" not "ramming down my throat".

Ramrodded because not proper notice or vetting, so Pluto huggers had already "czeched" out of Prague hotels and flown home, and because of the rude manner of Bell during the rancid session that went against the by-laws.

And, given that one IAU member voted against Pluto solely due to his career as an astronomer being threatened. He stated this publicly. Just because you say I am bullshitting doesn't make it so.

Who farted and made you the Queen of Sheba?

Mike, losing a vote is not having the results rammed down your throat.

"And, given that one IAU member voted against Pluto solely due to his career as an astronomer being threatened."

a) histrionic bullshit.
b) absolutely no reason to say it must be a planet
c) not the IAU's problem

You DO know people lie, right? Just because they say so, doesn't mean their assertion is right.

Who died and made you dictator for life?

a. I have no reason to believe he is lying, except to please you.

b.There are plenty of sound reasons for Pluto's replanetization or a petition with the sigs of 100s of planetary scientists would not exist protesting said rancid resoltion.

c. If bullying and intimadation and ramrodded were factors in the final vote to demote, yes, that is a problem, but that is not the only problem with the new def. It's problems have been well-documented. Earth doesn't even clear its path, bro. It has at least 19,500 asteroids that cross its orbit according to NASA.

d. At least I am not the Queen of Sheba, bucco!

a) what the hell do you think is going to happen to make him lose his job if pluto is going to not be a planet?

c) and if losing the vote massively (it wasn't even a close vote) is "ramming" then piss off to some dictatorship

d) you're a fucking idiot. This is not an improvement.

The final, third draft definition proposed on 24 August was:
“ The IAU. resolves that planets and other bodies in the Solar System be defined into three distinct categories in the following way:

(1) A planet [1] is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [3] orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".[note 1]

[1] The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

[2] An IAU process will be established to assign borderline objects into either dwarf planet and other categories.

[3] These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.
.
.
.
Resolution 5A constituted the definition itself as stated above. There was much discussion among members about the appropriateness of using the expression "cleared the neighbourhood" instead of the earlier reference to "dominant body", and about the implications of the definition for satellites. The Resolution was ultimately approved by a near-unanimous vote.

There seems to be this tiny rump of people still in denial of Pluto's non-planet status. The IAU didn't "ram" anything through anyone. What a bizarre conspiracy-theory.

Here's a question, though: bearing in mind the vast extent of the Kuiper Belt and the distribution of Pluto-sized objects already detected, can we predict how many more Pluto-sized objects remain to be discovered?

Additionally, if inhabitants of the Kuiper Belt have orbits that bring them within Neptune's orbit, then those objects are part-time Kuiper Belt objects, a new category?
Either that, or Triton can be a Kuiper Belt object despite having permanently emigrated?

Your first question was addressed in a recent Astron.J. article! See http://arxiv.org/abs/1310.7049, where they estimate about 12, with 9 already known.

The objects which spend "some time" in the Kuiper Belt, are referred to as "scattered disk objects" (see http://en.wikipedia.org/wiki/Scattered_disc).

The petition is even online. I didn't say ram. I said ramrodded. Pluto is larger than Eris and ever other KBO. Accept reality. Pluto will get its just desserts. Then your nuts will be numb.

I have stated the facts. If you think reality is bizarre, that is your right.

Here is the petition signed by 300 professional astronomers rejecting the IAU definition:
http://www.ipetitions.com/petition/planetprotest/

The claim that only a tiny group oppose the IAU decision is completely untrue. Many astronomers around the world continue to reject it and/or ignore it entirely. And this has nothing to do with winning or losing. The fact is, the IAU violated its own bylaws by putting a hastily thrown together resolution on the General Assembly floor without first having it approved by the appropriate committee. The IAU misled the original 2,500 astronomers in attendance by leading them to believe the original resolution approved by their appointed committee would be put to the General Assembly floor only to scrap that resolution and replace it with another one. The IAU was asked in 2009 by a group of planetary astronomers to reopen the issue and refused, clearly showing its leaders are more interested in their imagined "authority" than in real science. So far, only one other Pluto-sized object has been detected in the Kuiper Belt, and that is Eris, which according to the geophysical planet definition, is also a planet. Several objects roughly two-thirds the size of Pluto, clearly spherical and in hydrostatic equilibrium, have been found there, and these are small planets too. They all have stable orbits. The Scattered Disk is the outermost region of the Kuiper Belt where Eris is located. Pluto, Haumea, and Makemake are not in the Scattered Disk. However, Pluto Haumea, Makemake, and Eris can all be dually classed as both small planets and as Kuiper Belt Objects. The classifications are not mutually exclusive. The first tells us what they are the second tells us where they are.

"The claim that only a tiny group oppose the IAU decision is completely untrue."

Nope, it's completely true. They minuted the meetings and the results of the votes are available. You can check it yourself.

"Many astronomers around the world continue to reject it and/or ignore it entirely."

Meaning what? The definition is wrong? Nope. That a word means what you want it to mean, no more, no less? Well, THAT'S a knock-down, drag-out argument for you.

"The IAU misled the original 2,500 astronomers in attendance . "

Of whom very few thought that Pluto had to remain a planet.

"The IAU was asked in 2009 by a group of planetary astronomers to reopen the issue and refused, clearly showing . "

That a lunatic fringe who refuse to lose the vote will be ignored in the interests of getting something that means something done.

This isn't like a member meeting for "Shall we de-mutualise this building society" where you get to ask again and again if the majority of members vote "No" against the wishes of a few.

It was voted. Near unanimity for the proposal. Nothing to vote for again.

None of you loons seem to be able to say WHY it's so devastating that Pluto isn't a planet.

Hence I stick to my original assertion: it's a 'merkin invention, hence inviolate. 'Cos you is *special*, see.

"Here is the petition signed by 300"

Out of around 6500 possible signatures.

Yeah, that 300 aren't Spartans fighting the Persians, you know. 300 votes won't win a vote, no matter how much you whine.

I prefer to be a sparrow, not a loon, if you don't mind too terribly. There will be another vote, genius. Get over yourself. The definition is absurd and that's why it will go the way of the Dodo.

A proper case for Pluto wasn't made in Prague due to shenanigans already elucidated. Moreover, the vote was far from unanimous. Math not your forte, Holmes?

"I prefer to be a sparrow, not a loon"

And this is why you consider having lost the vote equal to being given the bird?

Near unanimous vote: resolution passed.
Result: Pluto not a planet like Earth, Mercury,Jupiter et al.

Net difference in the existence of Pluto: Nil.

For reasons which are apparent as long as you never look.

"A proper case for Pluto wasn’t made in Prague due to shenanigans already elucidated."

Yeah, those shenanigans being "don't let the lunatics run the show".

Actually, Earth has more in common with Pluto than with Jupiter. Both Earth and Pluto are rocky and geologically layered into core, mantle, and crust. Both Earth and Pluto have large moons formed via giant impact. Both Earth and Pluto have nitrogen in their atmospheres. In contrast, Jupiter has no solid surface whatsoever. Its composition is hydrogen and helium, very much like that of the Sun. Jupiter has a "mini-solar system" of moons and rings. Putting Earth and Jupiter in the same category but excluding Pluto makes absolutely no sense.

Many professional astronomers are not IAU members, so they had no say in this whatsoever. Furthermore, of 10,000 IAU members, only 2,500 attended the beginning of the 2006 General Assembly, and only 424 were left by the time the vote took place. Most who left early, including Dr. Owen Gingerich, chair of the IAU's Planet Definition Committee, said had they known a resolution other than the one they recommended would be put to the General Assembly floor on the last day, they would have changed their plans and stayed until the end. The majority of the 424 who did vote are not planetary scientists but other types of astronomers. To paraphrase Dr. Stern, that is like having divorce lawyers vote on a matter of corporate law.

Furthermore, the IAU is only now exploring the option of electronic voting for members who cannot be present at the General Assembly. Up to now, if a member wasn't in the room on that particular day, he or she had no say whatsoever. Many astronomers pay their own way to the General Assemblies and cannot afford to stay the entire two weeks. The 2006 vote was therefore representative only of those present in a room in Prague on August 24, 2006, not of all astronomers or all planetary scientists.

If you watch the video where the vote took place, it is obvious that some who voted did not fully understand what they voted for. Resolution 5a is the one that passed by a large margin, but that resolution only established the three categories of classical planets, dwarf planets, and small solar system bodies. Resolution 5b, which would have established dwarf planets as a subclass of planets, failed 333-91. Immediately after the vote, one astronomer tried to make a motion to add Pluto to the list of "classical planets" only to be told the vote was over. Clearly, at least one PhD present did not fully understand the resolution on which he had voted.

If you look at the list of 300 professional astronomers who signed the petition rejecting the IAU definition, you will find some of the world's leading planetary scientists--hardly a "lunatic fringe." Wow, I don't know where you get the "out of 6,500 possible signatures." Who are you counting? The petition was kept open only for three days to make an immediate statement.

This is not about winning and losing and it is not about wanting Pluto as a planet. It is about an attempt to force a highly problematic planet definition on an entire field and on the world, a definition that amounts to interpretation rather than fact. This isn't even something that should be voted on. Did anyone vote to accept gravity or relativity? Did anyone vote on whether the universe has one or many galaxies? The answer to all these is no. It is the facts, not someone's interpretation of the facts or a vote on whose interpretation is liked better, that ultimately determines what is what in science.

Your unmitigated hate and spleen is looney toony. Your case is non-existence, and your sense of humor is that of a wooden spoon. The Dark Side won on the 434th anniversary of St. Bartholomew's Day Massacre, but the forces of Light haven't been extinquished. 300 distinguished scientists signed that petition,and that is just the tip of the iceberg, Holmes. Yes, you won a vote by 333 to 91 that day due to unspeakably disgusting shenanigans, but a new day dawns every day, dude. Moreover, the case for Pluto grows every day. Bruno Sicardy of the Paris Observatory wrote a paper saying data strongly suggests Pluto is at least 12 km larger than Eris in diameter, for example. We know Earth doesn't clear its orbit by a long shot. We know rogue planets do not fit the defintion, too. It is a weak, politically-driven definition whose supporters are trolls and other miscreants. That definition's days are numbered. Why are you so misled, dude? Are you one of Mike Brown's lackeys?

“The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is.”

"Both Earth and Pluto are rocky "

So is the stone in my shoe, however, it isn't a planet.

So is Ceres, but that's not a planet.

So is Titan, but thats not a planet.

Pluto is 1/5th the diameter of Earth, which means less than 1% its mass. Or about 2/3rds the earth's moon.

"Both Earth and Pluto have large moons formed via giant impact."

Charon wasn't created by the same process. Moreover, our moon isn't a normal way to get a moon.

"Furthermore, the IAU is only now exploring the option of electronic voting for members who cannot be present at the General Assembly"

This does not make the vote before wrong.

"If you watch the video where the vote took place, it is obvious that some who voted did not fully understand what they voted for."

Really? But these people know how to decide what's a planet?

"Resolution 5a is the one that passed by a large margin, but that resolution only established the three categories of classical planets"

No, resolution did not define classical planet. Indeed the resolution for that lost on a small majority.

Sorry, when you call on us to take it as "truth" that "clearly some did not know what they voted for" asserted by merely watching a vote WHEN YOU GET THE RESOLUTION VOTED FOR WRONG, it *really* doesn't build your case.

"Your unmitigated hate and spleen is looney toony."

Because WHO was it who said that a lost vote was "Ramming down [others] throats"? Was that you? I think it was

“I my be drunk but in the morning I will be sober, whilst you will still be an idiot"

"300 distinguished scientists signed that petition,and that is just the tip of the iceberg,"

Just like all those proofs of alien visitation will be leaked "any day now".

The word "Planet" comes from The Greek meaning 'Wanderer" since these objects "wandered" about the sky.

I see you are rambling now. Have you been drinking? Yes, I said "ramrodded." Ceres was a planet, of course, and is now a dwarf planet thus, when Pluto is replanetized, so will Ceres as it meets every logical requirement to be a planet. Just like a chihuahua is still a dog. It does not matter if the particular chihuahua is on the small side as far as chihuahuas go, or if the chihuahua was born in America or in France or in Burkina Faso. I was not around when Charon was created, so I will not chime in on that one. Just how old are you?

Resolution 5a NEVER said that dwarf planets are not planets. Many who voted for 5a also voted for 5b. Advocates of a geophysical planet definition have no problem with 5a, but they also support 5b, which places both planets (at times referred to as "classical planets" during the discussion) and dwarf planets under the broader umbrella of planets. 5a would be even better if it subdivided "planets" into terrestrials and gas giants/jovians.

The only mass that matters, at least to the geophysical planet definition, is the threshold for an object being in hydrostatic equilibrium, meaning rounded by its own gravity. The stone in your shoe is not in hydrostatic equilibrium, and it is already part of an existing planet. Ceres, being spherical and in hydrostatic equilibrium, IS a planet 19th century astronomers' telescopes were not powerful enough to resolve it into a disk, so they didn't know this. Titan and Earth's moon can be considered as satellite or secondary planets. Their structures, compositions, and processes are very much like those on the primary planets the only difference is that these objects orbit other planets instead of orbiting the Sun directly. Moons of giant planets in other solar systems may very well be capable of hosting life.

Is there a "normal way" to get a moon? One could answer no there are many ways in which planets can get moons. Triton appears to have been captured by Neptune. We are still learning how Earth's moon formed, and the fact is, it and Charon are the only known large moons in this solar system to have formed via giant impact. Discoveries of exoplanet systems are continually sending scientists back to the drawing board when it comes to understanding the formation of solar systems and planetary systems.

If you watch the video of the vote, you can tell that there was a strong emphasis on time constraints and that these resolutions were rushed through with so many last minute changes to the point that many in the room did not have the time to fully process the resolutions in detail. Moreover, the ongoing discoveries of exoplanets and new knowledge about objects in our own solar system (such as Dawn's discovery that Vesta is more like a terrestrial planet than like an asteroid) are themselves a compelling case for revisiting this issue.

Let's say you discovered a new object, possibly a planet and then years later other folks came along and dissed your discovery?

Of course I ask this question in all sincerity because I have discovered but I don't know that you have.

I think you wouldn't like it very much!

"Well, Steve, lets look at the questions in #47.
" As where I get rock dwarf from, hmm. do the words “gas giant” ring any bells for you?" - StevoR
Answered. My query about “What the fuck does that have to do with it” went unanswered. Responded? Yes. Answered? No." - Wow

Answered and rebutted yes actually as reasonable people can see from reading comments # 53 & 60 here.

"Next:
“Seeing as I’ve answered all your points, you care to reciprocate and finally answer my earlier questions in this thread in comments 33, 39, & 41? ” -StevoR
Seeing as you didn’t answer them…
But that seems to be the only two questions.
One answered and the other a “russian doll” one and insisted on being answered because you confused a reply with an answer." - Wow

No, Wow, its you who is very confused - or are being deliberately obtuse and just trolling here. My actual questions which you have repeatedly ignored and failed to answer were & remain :

1) Why do you ("Wow") think Pluto is NOT a planet precisely?

2) Did you read the links I’ve provided for you and try answering Croswell’s Pluto questions? How did you do and what do you think of them?

3) Do you you think that having enough things that are X together suddenly somehow makes X into not-X?

(E.g. if enough people gather into a crowd do they stop being people? Do animals stop being animals when they gather in herds and as the answer to both of those is clearly not so must it be with planets - getting a lot of planets in one - rather huge - area together doesn't stop them being planets either.)

Those are the questions I was referring to and which you have continuously failed to answer, Wow.

As for abusing me in all caps and constantly merely insulting me and others who've rebutted your weak excuse for arguments well, you've really given the game away there on your trolling here and own lack of class and ability to argue rationally. You have demonstrated yourself to be a troll of very low intellectual and ethical quality indeed.

"There seems to be this tiny rump of people still in denial of Pluto’s non-planet status. The IAU didn’t “ram” anything through anyone. What a bizarre conspiracy-theory…Get over it."

Its no conspiracy theory but the reality as the facts of the Prague IAU meeting show.

Nor is it just a small group who disagree with an IAU definition that gets ignored and shown to be ridiculous every time someone describes an exoplanet as just a planet.

Since "Wow" (full name - Wow what a troll?) is clearly incapable of answering my questions, maybe you could give me your answers to them, Craig Thomas please?

"Here’s a question, though: bearing in mind the vast extent of the Kuiper Belt and the distribution of Pluto-sized objects already detected, can we predict how many more Pluto-sized objects remain to be discovered?"

The search has been going on for a very long time and we still haven't found anything larger than Pluto and Eris. That seems to suggest that bodies that size are relatively rare and most of the major one's have already been discovered at least in the Edgeworth-Kuiper Cometary Belt (EKCB) region. Maybe larger objects still await discovery out in the more distant reaches of Oort Cloud.

I expect the search to continue and answers eventually will come.

"Additionally, if inhabitants of the Kuiper Belt have orbits that bring them within Neptune’s orbit, then those objects are part-time Kuiper Belt objects, a new category?"

As well as seconding the answer given by Michael Kelsey at #78, I'll add there is a class of objects that cross the orbits of outer planets and can swing far out into the Edgeworth-Kuiper cometary belt classed centaurs named following the discovery of the large asteroid / cometary nucleus Chiron in around the late 1970's-early 1980's.

These objects - like comets generally - originated further out and have migrated inwards over time into unstable planet-crossing orbits.

"Either that, or Triton can be a Kuiper Belt object despite having permanently emigrated?"

I think it makes more sense to say that Triton was the "King of the Kuiper belt" but then migrated inwards and was captured by Neptune becoming its largest moon. IOW Triton used to be a member of the EKCB but now isn't anymore although a mission to Triton would certainly tell us about EKCB objects because of its past history although much of its original surface will have been heavily affected and modified by its capture into retrograde Neptunian orbit.

@94. Wow : “I my be drunk but in the morning I will be sober, whilst you will still be an idiot”
— Winston Churchill."

You are certainly no Winston Churchill Wow.

When (if?) you ever sober up, Wow, sadly you will likely remain an idiot and / or obnoxious troll judging by your comments here.

@P Edward Murray : "The word “Planet” comes from The Greek meaning ‘Wanderer” since these objects “wandered” about the sky."

Correct. Pluto and Eris and the other ice dwarfs wander across the sky too - just relatively very slowly because of their distance. Of course we now know of them and of much more than the ancient Greeks could have imagined.

“Your unmitigated hate and spleen is looney toony.”
Ah. Irony is this? Because WHO was it who said that a lost vote was “Ramming down [others] throats”? Was that you? I think it was
[sic]"

Thing is the statement about the Pluto vote being rammed down people's throats is factually accurate and you have, in fact been attempting - unsuccessfully - to do that ramming yourself thus disproving your own supposed point.

Meanwhile, Wow, your own comments clearly reveal that you *are* indeed as described above a bit of a loony tune or at pretending convincingly to be so with comments that are hateful as well as tiresome , abusive, lacking in reading comprehension and lacking in any substance and logic.

"You are certainly no Winston Churchill Wow. "

Was that meant to be a zinger, Steve?

Let’s say you discovered a new object, possibly a planet and then years later other folks came along and dissed your discovery?"

That's what happens ALL THE FUCKING TIME you moron.

Dawn Horse? Renamed because the first fossil was misidentified as belonging to an early hippo.

Brontosaur? Renamed because the first fossil was named by someone else.

Moreover, where do you think pluto went when it lost its planet status? Do you think it wandered off in a sulk to find another star where it could be called a planet?

Lastly, that's fuck all reason for Pluto to be called a planet.

"Resolution 5a NEVER said that dwarf planets are not planets."

5a said that Pluto wasn't a planet. 5b (may have been 5c) asked for a definition of "classical planet" to be added to give three subgenera, but it lost by a moderate, but not large, margin.

And that was hateful, spiteful and vindictive reattribution of a fair vote you lost.

Steve, your entire bullshit is still FUCK ALL reason for Pluto to be a planet.

Your original assertions were shit and did nothing to help other than beg the question of whether Pluto should be a planet at all.

Your subsequent bullshitting, like Mikes, merely increased the special pleading and nonexistence of any reasoning for Pluto to be required a planet.

"Someone said they'd lose their job!".

"How would you like it if your discovery were dissed".

It was by any measure dissed by being originally thought 10x heavier than it was.

Why does that mean Pluto should be a planet merely to make someone happy?

"Yeah, but that's just the tip of the iceberg!"

Yeah, of course it was. Now go and put yourself back in that padded room, lunatic.

"Yeah, well, you're no Winston!"

Oh, that was supposed to hurt?

"Thing is the statement about the Pluto vote being rammed down people’s throats is factually accurate"

Nearly unanimously voted for Pluto not being a planet.

If it had gone the way you wanted, how would it NOT have been even more "ramrodded" down the vast majority of throats?

"1) Why do you (“Wow”) think Pluto is NOT a planet precisely?"

Because it doesn't meet the requirements for a planet, you fucking idiot.

"2) Did you read the links I’ve provided for you and try answering Croswell’s Pluto questions? How did you do and what do you think of them?"

"3) Do you you think that having enough things that are X together suddenly somehow makes X into not-X? "

Note, Steve, that that Q3 was completely vapid shit and I had to guess that what you REALLY wanted was

Do you think that Planets that included Pluto in their list can no longer include Pluto in their list if the definition of Planet includes scores or even hundreds of objects. Because there's no consistent X that could be inserted into that asinine and confused query that would make ANY sense.

. definition of Planet that can include Pluto in their list also.

Here's a reason why Pluto shouldn't be a planet: Gustav Holst's "The Planet Suite" doesn't have Pluto in it, therefore if Pluto becomes a planet, you're making his masterpiece wrong!

How would you like it if someone came along and made your orchestral master work wrong, huh?

The vote was not fair. It was ramrodded. You think a ramrodded vote can be fair? Looks like you are the dictator. Stalin would be very proud of how the IAU ramrodded the demotion of Pluto down the throats of the general membership. So would John Holmes and Ron Jeremy.

I never heard of Gustav Holst. He is no Mozart and you, Sir, are no Churchill.

People continue to say that, but the only "reason" they give is that proposal was passed and as a result Pluto was declassified as a planet.

The fact that a vote has an outcome of which you disapprove does not mean there were shenanigans during the vote.

The big question I have is this: what real difference does the result make? Why are people upset about this?

"I never heard of Gustav Holst."

And I never heard of anyone who said they were going to be made unemployed if Pluto wasn't a planet. Does that mean he doesn't exist?

No, that's why he has a different name, Mike.

That's how you tell different people apart, generally.

This public information bulletin brought to the local internet idiot by a helpful stranger.

"The vote was not fair. It was ramrodded."

As dean says: "I lost" does not define "ramrodded", moron.

The vote was ramrodded because of reasons listed ad nauseum by Laurel Kornfeld and by me. Don't be coy with me, Mr. Wow. You know very well I am not saying that the mere fact of losing a vote constitutes ramrodding. Perhaps if you engaged your mind instead of your knee-jerk trollness, you would realize that you are on the wrong side of the issue.

As far as Gustav goes, maybe I will listen to his so-called masterpiece someday. He is not really part of the problem here.

The problem is ramrodding.

"The vote was ramrodded because of reasons listed ad nauseum by Laurel Kornfeld and by me."

1) Someone said they'd lose their job
2) They got the wrong answer

These are not reasons, dear.

Oh, forgot another "reason" you listed:

3) 300 people signed a petition!

No notice. No vetting. Earth doesn't clear its orbit, either. 300 distinguished scientists. Not 300 trolls, honeypie.

Mike, you seem to confuse personal anecdote with evidence (proof, if you will). You still haven't made your case - or, equally curiously, explained why it is (to you) so massively important that Pluto remain in the planet category.

I don't. As far as anecdotes about why I like Pluto, such is not relevant here.

The case has been made ad naseum, dean.

It is very sad, pitiful, and pathetic that in a purely scientific debate such as the status of Pluto and the other dwarf planets, the pro-Pluto side is demonized in a most juvenile manner as idiots, numbnuts, "unable to understand the difference between fact and anecdote," et cetera. Also, I have been told repeatedly to make a case then this thread is about a mile long, much of it devoted to the making of a case. Derp.

You guys are a trip and a half. Why don't you read Alan Boyle's book entitled "The Case for Pluto" if you are unable to process the case on this thread. You can ask for it for Christmas or Nationa Puppy Day or whatever. That is all.

Gustav Holst's "The Planets Suite" does not have Earth in it either, so I guess according to you, Wow, Earth isn't a planet.

Resolution 5a never said that Pluto wasn't a planet. It simply listed three classes of objects--planets, dwarf planets, and small solar system bodies. Resolution 5b would have combined the first two classes of objects under the broader umbrella of "planets."

The footnotes to these resolutions were a source of tremendous confusion. The executive committee went back and forth about whether the footnotes "counted" as part of the resolution multiple times, to the point that even those who voted were confused. The footnotes to 5a listed Mercury through Neptune as planets, contradicting the main portion of the resolution, which set three categories but left the planet status of dwarf planets up to 5b. There was no resolution 5c. All this was done in direct violation of IAU bylaws because none of these resolutions was first vetted by the proper IAU committee.

If having enough things that are X together suddenly somehow makes X into not-X, then stars in dense clusters should not be considered stars, and galaxies in dense clusters should not be considered galaxies.

This is not about winning and losing. Stop thinking in terms of a football game. It is about a poor decision made hastily by people who are not experts on planets in a process that excluded far more astronomers than it included. People inherently understand the political nature of these shenanigans they know what happened in 2006 was not science. That is why so many, including knowledgeable professional and amateur astronomers, continue to oppose that decision.

"Gustav Holst’s “The Planets Suite” does not have Earth in it either"

Planet means "Wanderer" and refers to a "star" that wanders across the earth's sky.

The sky is the bit that doesn't include the earth itself.

You mean apart from the 10 days spent arguing over it?

You mean allowing people who are at the IAU meeting to vote and not checking that they all are morons who "wanna Pluto. "?

We know you don't. You have to if you want to explain why it has to be a planet.

"As far as anecdotes about why I like Pluto, such is not relevant here."

It is entirely relevant. See above.

"the pro-Pluto side is demonized in a most juvenile manner as idiots, numbnuts, “unable to understand the difference between fact and anecdote,” et cetera. "

Well lets see what evidence we have here, since we're scientists, right?

Juvenile? No evidence given against me on that score.

Idiots. Well, see the "He said his job was gone if Pluto wasn't a planet and I believed him!". So it appears that there's evidence there.

numbnuts. You have "Ramrodded" as a synonym for "accepting the voting majority" and insist that this is, without any evidence, fact. Appears to be evidenced.

"Cannot distinguish between anecdote and fact". Well, for a start, it was "evidence". And you've had "someone would lose their job. " as "evidence" that shows Pluto has to be a planet. Another evidenced based observation.

"This is not about winning and losing."

Weird. Ever think of doing that yourself?

One proponent of making Pluto a planet claims:

"That's what everyone said, and that's what everyone had said since the last planet - Pluto - had been discovered way back in 1930."

Ceres: 8th Planet (1801) Became Asteroid (1851). Now Dwarf Planet.

Neptune. 13th Planet (1846). Now 8th Planet.

When the argument for Pluto remaining a planet is "It's been one since 1930", that is no argument for it, merely "It's what I was taught, dammit!". But even then, when it's based on a LIE, then there's no argument at all.

In the case of this lie, there are two options:

1) They know they lied, in which case, they know the argument is false.
2) They didn't know. But in this case, how can they be held as having valid opinion when they have heard a "factoid" and never even checked the basics about it? So here, rather than malice, it's sheer incompetence.

This is not about winning and losing.

Yet that is what your posts seem to be making it: you (and others, I am not laying it all at your door) have done nothing but state, in long terms, that you are upset at an outcome you do not like.

It is about a poor decision made hastily by people who are not experts on planets in a process that excluded far more astronomers than it included.

This comment leads me to my other question (again): if you are concerned about Pluto being declassified, there must be (or would be, in a logical argument) some reason, scientific, not personal, that the decision is troubling. The fact that you cannot or will not state one leads this observer back to the thing you so heartily deny: that is really is about "winning and losing", and you are upset that your position "lost". The supplied "arguments", being merely more whining from others, don't change that fact.

"The fact that you cannot or will not state one"

Well, apart from shilling a book to buy, rather than state what, in that book, makes them think Pluto should be a planet.

And a book whose sales, no doubt, are used as "proof" that Pluto should remain a planet.

Shilling? Stop whining, dude. You can keep reading Mike Brown's narcissistic tripe if that's your thing. At least it will spare me from your jejune posts for a few hours.

Yes, you do know what "shilling" means, right?

So mentioning a book to you is a bad thing and will automatically make you say I am shilling. Grow up. Okay, don't ever read another book. Stick to Sesame Street and Nora the Explorer, but just stop whining about how people are shilling. It is very annoying and immature. It is also a very easy insult. I think you can do better than that. It is a soft target.

I have said ramrodding is not the same as being on the wrong side of a vote. So it seems I am wasting my time having a dialouge with you. You are like a parrot, constantly accusing me of the same things. If you think I am going to share personal, anecdotal stories with a person who flings insults at me, you are gravely mistaken. Moreover, despite your best attempts at persuasion, they have no relevance to the case for Pluto and dwarf planets whatsoever. There is plenty of evidence and strong arguments for dwarf planets being a subcategory of planets. For example, the sun is a yellow dwarf star and also a star. Why are dwarf stars considered stars, yet dwarf planets not considered planets? The same is true for dwarf galaxies. The IAU had it out for Pluto. We know this. Circumstantial evidence exists to prove this beyond a shadow of a doubt in the minds of those who are not delusional and resort to calling people idiots,morons, and numbnuts. I realize you will never question why the sun is a dwarf star and also a star yet Pluto only a dwarf planet because you are interested in "winning" your little blog battle with me and Laurel, but some people are actually intellectually honest enough to consider the arguments made by differing points of view. To repeat another point you have consistently ignored, Earth has at least 19,500 asteroids that share its orbit, as counted by NASA and reported a few years ago. What you do with this evidence is up to you. I suggest you do more with it than play with it along with your Dora the Explorer doll, but do with it what you will.

"So mentioning a book to you is a bad thing"

Saying "Buy this book" is a shilling thing.

Saying "Read this book" rather than explain what it is you think it contains that is pertinent is a bad thing.

Saying "Shilling? Stop whining, dude." rather than point out any argument in the book that you think relevant is a bad thing.

Saying "Urg" rather than any actual sentence of any relevance is a bad thing.

Saying "So mentioning a book to you is a bad thing" when that is another strawman to avoid any actual content is a bad thing.

These are bad things that you do. Just because you do them does not mean anything you think can be upbraided as ridiculous when you strawman them.

I have said ramrodding is not the same as being on the wrong side of a vote.

dean has said ramrodding is not the same as being on the wrong side of a vote.

NEITHER of us have said you have said "ramrodding is not the same as being on the wrong side of a vote.". That is yet another strawman.

You and others have said that you lost the vote is ramrodding the voted decision down your throats.

Which isn't saying that losing the vote is the same as being on the wrong side of the vote, but saying that your being on the losing side of the vote is the only reason you're calling it ramrodding.

"To repeat another point you have consistently ignored, Earth has at least 19,500 asteroids that share its orbit"

None of which cause any orbital perturbation to the earth, therefore it has cleared its orbit.

Pluto is massively locked to Neptune and therefore is as locked to it as we are to the sun.

Therefore Pluto has not cleared its orbit.

Just let it go, dude. I mention a book and you get all bent out of shape like I am Hitler or something. What is wrong with you? If I said buy it (and I am not going to scroll and see what exact verb I used) then I am sorry. Go to the damn library, but whatever you do, do not check out that book, rather, check out Mike Brown's tripe. Or check out a Nora picture book. Geeze, why can't you let things go? You are the one obsessed with "winning."

I said Ugh, nor Urg. I didn't have the time or patience to say anything else at the time, but wanted to express my frustration and disgust at having to deal with your incessant misconstructions of my posts. You should consider taking up comedy. Maybe you could make a few drunks laugh at the end of the night before they waddle off to their cars.

As far as Pluto being locked to Neptune, I will have to check up on that. I know Pluto and Charon are tidally locked. I do not pretend to know everything.

I used ramrodding in the context of the holding of the vote. Why did certain members go home and other not? Why was one person threatened? Could it be that the Exectutive Committee hand-picked and choose who they told about the vote on Pluto on the last day of the GA, while letting known Pluto huggers fly away from Prague before the said rancid session? Yes, perhaps the ramrodding began even before the actual session. Had the vote been fair and square, with proper notice and vetting, and without anecdotes of intimidation and threats, I wouldn't have used the term ramrodding, even if the vote went the way it did.

I know what ramrodding means and used the term correctly. If you want to continue to beat this horse, you may, but I will have you know it is quite dead.

Do you have any other fake gripes with my posts to bitch about?

" I mention a book and you get all bent out of shape"

1) kept banging on about the book rather than state your own opinion
2) not bent out of shape, calling you out on your empty blatherings

"As far as Pluto being locked to Neptune, I will have to check up on that."

THIS, THIS RIGHT HERE is why the pro-pluto fellators like yourself are fucking moronic buffoons with nothing to say:

RESEARCH YOUR FRIGGING SUBJECT FIRST.

But I suppose it's the moron charter: have an opinion, make it strong, and FUCK informing yourself before getting one!

Jesus minging fucking christ, before you fuck about with how pluto is all a planet, like, and the entire IAU assholes, how about you first find out what the hell you're on about first?

Or is work too difficult for you?

"I know what ramrodding means and used the term correctly"

"Why did certain members go home and other not?"

Why did certain members decide to go home rather than vote?

"Why was one person threatened?"

Because he was threatening others and told to play nice or eff-off?

"Could it be that the Exectutive Committee hand-picked and choose who they told about the vote on Pluto on the last day of the GA"

It's possible. Just as it's possible that yesterday is a figment of your imagination, impregnated there by a malicious god having a laugh at your expense.

Could it be that the executive merely tried to get agreement and this takes time and that the result is just what people who have something relevant to say agreed on it?

"Yes, perhaps the ramrodding began even before the actual session."

Yes, perhaps this is all a ploy by the Jewish State to manipulate the markets to allow the Lizard Alien Overlords who have dressed up as the Windsors to get the UK working for the subjugation of humanity. Perhapes this goes all the way back to the formation of the Jewish "family" of the Rothschilds, back to 400BC.

"Had the vote been fair and square, with proper notice and vetting"

The vote, however, isn't one you like. So it MUST be a conspiracy!

You are probably making that whole Neptune thing up. Pluto has its own orbit, dude. There is a theory that Neptune has something to do with Pluto, but that is all it is. Pluto has hydrostatic equilibrium and an atmosphere. It is a planet. Rogue planets don't even have an orbit and are planets. You failed, again, to tell me why a star can be a dwarf star and a star. Probably because you have no glib retort at the tip of your tongue. I used ramrod correctly. Just because you blather on doesn't make my usage incorrect. You are the one obsessed with "winning" here, blathering about the Jews and pissing and moaning that I mentioned that you might want to read a book. Please don't read that book, ever. In fact, please never read another book, because I might be blamed for that, and I will have to read more of your bizarre posts about how I forced a book down your throat. Oh, and go ahead and think Pluto is a comet or whatever twisted thing you might think Pluto is, even though some of the greatest scientists in the world think it is a planet. Your opinion clearly is not based on fact or science. You have a little bit of knowledge, and enjoy pistol-whipping people with it.

"You are probably making that whole Neptune thing up."

Yeah, and I went and edited all the books on astronomy to do so!

Seriously, you believe a guy who claims he's out of a job if Pluto doesn't remain a planet because "[you] have no reason to believe he is lying, except to please you." yet you believe I've made it up WITHOUT EVER LOOKING merely to please yourself.

PS yet more strawmen arguments off you you internet retard.

Mike, you do realize that this was the end result of a search to find a definition of a planet don't you? That there had never been a specific definition? That an earlier suggestion (prior to the meeting) would have kept Pluto but also included numerous smaller bodies, and that was met with a great deal of resistance, correct?
The fact that Pluto has had a special emotional place for many people is understandable, but it is not a scientific reason for keeping it as a planet.
Your repeated complaint that the Earth's orbit is not cleared is stating only part of the problem: Pluto's orbit is filled many things <b which are similar to it while the other planets' orbits are not. It is fundamentally different in that respect, despite your assertions to the contrary.
Finally, it should be noted that the voting process was not different than that used for other issues - again, despite your assertions to the contrary.
You haven't provided any scientific reasons the result is incorrect: all your claims, and your references, boil down to "it is wrong because we don't like it and Pluto deserves to be a planet". I return to your refusal to provide your own reasons for doing this: I believe you realize the science is not on your side and that your argument is sentiment-based only. Being passionate about an issue can be good, but passion alone does not make a scientific argument.
I'm not sure why you've decided on this to be your personal windmill to chase. However, you would be taken more seriously if your comments were in the least sense based on the facts rather than on opinion, second/third level anecdotes, and foot-stomping.

I would appreciate it if you wouldn't paint me in a false light, a caricature. I have stated numerous reasons. One that neither you nor Wow has addressed is why the sun is a star and a dwarf star and why dwarf galaxies are also allowed to be galaxies. I was not born yesterday. I have two degrees. I know the difference between objectivity and subjectivity. I am not merely stating opinions. So give me a break. You want to turn me into a strawman so you can think this issue is over and done with. It is not. The science is continually rolling in. Bruno Sicardy's date suggests Pluto is larger than Eris, for example. If you want to harp on the fact that I mentioned a book by Alan Boyle like Wow ad nauseum, go ahead. I am tired of these baseless accusations that I am being subjective. Speak to the substance of my posts, please. Both you and Wow seem to have some intelligence, so why must you continually put me down and dismiss me? It is too easy, dude. You are talking down to me like I am the student and you are the teacher, or I am a singer on American Idol and you are Simon. I am stated arguments that both of you have not addressed. Try looking inside yourself instead of kicking me in the nuts for a nice little change of pace. The vote in Prauge was tainted. The resolution was specifically tailored to demote Pluto. Moreover, there is anecdotal and circumstantial evidence that it was done purposely. Therefore, it would be best to reopen the debate. Alan Stern thinks the new definition of a planet is a farce. He is a distinguished planetary scientist. Are you and Wow going to try to kick him in the nads, too?

As far as the orbits of Earth and Pluto being different, fine. No orbit of any planet is the same. The fact remains that if Earth was in Pluto's orbit, it would not clear its path. The further a planet is from our dwarf star, the larger it must be. This means that what is a planet in one area would not be a planet in another area. Therefore, the current defintion is arbitrary and capricious. It was also quickly whipped up on the last day of the 2006 GA. Such a definition doesn't do justice to our wonderful solar system.

"I would appreciate it if you wouldn’t paint me in a false light, a caricature."

Begging the question: is it false?

"One that neither you nor Wow has addressed is why the sun is a star and a dwarf star and why dwarf galaxies are also allowed to be galaxies."

Note, by the way, two other "points" raised by you were answered and nothing ever changed about your assertions when they were debunked.

Pluto is a dwarf planet. Earth is a planet.

They both orbit the sun. But that's where their similarities end.

Pluto is a dwarf planet. Mercury is a planet.

They both orbit the sun. But that's where their similarities end.

Pluto is a dwarf planet, not a planet.

What, precisely, is your problem on that score?

"No orbit of any planet is the same."

Not in the definition of a planet, dear.

"The fact remains that if Earth was in Pluto’s orbit, it would not clear its path"

"“The fact remains that if Earth was in Pluto’s orbit, it would not clear its path”

Depends what you are trying to say.

If Earth being tidally locked by Neptune and Neptune orbit crossing, then, yes, Earth would not be a planet.

Why is this a problem for you? If ducks were horses, would you ride a duck, not a horse?

However, if the Earth were at Pluto's distance and retained the "cleared its orbit", which is true for Earth in its orbit, then it would be a planet because it has cleared its orbit of perturbating influences on its trajectory.

Dean, I wonder if this isn't merely another anti-science person finding SOMETHING to claim that scientists (who exist in ivory towers and are not *really* human) are evil scum of the earth, declaring everyone else has to bow to their edicts.

You know, same as the whine about "LHC could DESTROY THE EARTH. ".

Do you know what "clearing its orbit" means? It means an object must be massive enough to absorb smaller objects in its path or so that its gravitational field can move them. The Earth fits that (it is, if I remember correctly, nearly 2 million times the mass of other items in its orbit.)
Stern does try to argue (with a more scientific basis than has been demonstrated comments above) that the Earth should would not be considered a planet according to that requirement, but he has failed to be convincing to his fellow scientific community. He also states that having only 400 out of 9000 IAU members vote could not give a representative choice, an interesting argument. Over 2000 people were registered at the conference, approximately one-half were at the session where the vote took place. For some reason, ('only") roughly 400 of those found the proposal important enough that they took part in the vote. The 400 hardly constitute a random sample, but a case could be made that the population of astronomers who were interested in this issue were the 1000 in attendance, and the voting group is a large (self-selected) sample. You could (I would have to think more) argue that the 400 voters were THE population to whom this issue mattered most strongly, and so the fact that the vote went strongly in favor of the proposal would then indicate that there is no serious opposition among those showing an interest.

Now this was hardly a case of "ram-rodding" (whatever that non-defined word means) a vote. The notion that the proposal was written at the last minute is deceptive at best: there had been three different proposals being discussed and reviewed in the time leading to the vote: discussions held, objections and suggestions for changes were made. Some of the items were changed, some weren't. During the pre-vote floor discussion of the final proposal some suggestions came from the floor on how the points included could be made more clear some were implemented. So yes, discussions went down to the wire, but do not attempt to say this was all done in secret and sprung on a collection of the uninformed at the last minute, immediately before they were to leave that is not the case.
I will also note that the petition you mentioned was, in short, laughable: only 79 of the 9000 IAU members signed it: most of the people were not scientists with any understanding of the issues (one person is apparently quite unhinged about science, believing some nonsense about viruses originating from Venus and being flown to Earth by the solar wind). Why should the opinions of non-experts for this issue be taken any more seriously than the opinion of non-experts on whether creationism should be given equal footing with evolution? (Hint: they shouldn't)

It is relevant that dwarf stars are stars and that dwarf galaxies are galaxies and that dwarf planets are not planets. Therefore, it is obvious that both of you are being subjective and that this issue is too personal for either of you to present a cogent case against dwarf planets being a subclass of planets. 300, not 79, scientists signed that petition. One of them is David Rabinowitz, a co-discoverer of Eris. Imagine that. How you dream up that I am anti-science is another sign of your delusional behavior. There has been nothing I have written here to suggest I am anti-science. Dream on.

"It is relevant that dwarf stars are stars and that dwarf galaxies are galaxies and that dwarf planets are not planets"

One is about stars, and brown dwarfs are "failed stars".

The other is about galaxies (and dwarf galaxies are not, strictly speaking, galaxies, just like globular clusters around our galaxy aren't galaxies either: scale DOES matter).

And the latter is about planets and Pluto isn't a planet like Earth, but a dwarf planet like Ceres.

"it is obvious that both of you are being subjective and that this issue is too personal for either of you to present a cogent case"

It's always projection with you idiots, isn't it?

Where is YOUR "cogent case"?

"One of them is David Rabinowitz, a co-discoverer of Eris. Imagine that."

More than 3x as many have no connection with the matter voted on and only after it's been made are whining. Those who could conceivably claim to have been excluded are less than 1/4 of that pitifully small petition.

But yet again, rather than have your own ideas, you merely shout "SQUIRREL!" and whine about how you're being persecuted.

300, not 79, scientists signed that petition.

Perhaps we are referring to two different petitions - possible, but not likely, and if not, the 300 is a false number.

But, even if you correct: what percentage of (approximately 9000) is 300? Is 300 greater than the number who thought it important enough to vote?

Side note: Mike Brown, co discoverer of Eris, stated (after joking that if a probe discovered a sign on Pluto that read "I'm a planet" he would change his mind) this:

But barring that there’s really nothing we could learn about Pluto that would change the fact that we know enough to say that it’s really part of this other population.
It doesn’t really fit in with the planets it’s part of this other population. It’s really the size and the mass and its location that makes a difference.

Since you like spouting out items from authority, consider your latest one cancelled. When asked how he felt about the term "dwarf planet", he stated (emphasized item by me)

It’s OK. I don’t like the term “dwarf planet” because it sort of confuses people by having the word “planet” in there. It’s unnecessarily confusing. It makes people say, “Oh, so isn’t it still a planet?” No, it’s not a planet. So I would have preferred a different word, but it’s serviceable, and I am willing to go along.

Dump the persecution complex: the explanations have been attempts to show that your assertions of "ram-rodding" and other shenanigans don't hold water. If you choose to ignore the facts about the debate, or the numbers of people who attended versus number who found it important enough to vote, or the fact that "petitions" collect relatively few scientists as opposed to civilians who, for whatever reason, don't like the change, fine, you don't have to. If the facts of the case don't sway you then they don't: they should let other people know that the way you assert things went down are demonstrably false, and that the level of objection in the scientific world is not as high as you want to make it seem to be.

Yellow Dwarf Star. Our sun. Also a star. What is there not to get?

Brown Dwarfs. Not Yellow Dwarfs.

You blind as well as fucking stupid?

I could care less about your blather about brown dwarfs. I make my points and you make yours. Deal?

You seem like a nice guy, so I will say this real nice. Quoting Mike Brown doesn't impress me. The guy told his wife he discovered a planet when he co-discovered Eris. Now he claims he killed Pluto. I could start quoting Stern and Tombaugh and Disney. Did you know Brown publicly beheaded a doll of Disney's Pluto. He is a buffoon. A pathological narcissist. His book is tripe. Garbage. He never corrects book reviewers who say he discovered Eris or that it's larger than Pluto. You'd do better to quote Xena the Princess Warrior.

My allegations of shenanigans, moreover, are water-tight. The vote was hopelessly tainted.

The point is that trying to make an argument based on comments of "authorities" is not way to make an argument.
I'm not sure about your "corrects people who say he discovered Eris" - he was on the team that discovered it. Notice, also, that initially it was believed that Eris was larger than Pluto. Current measurements show it to be more massive, and the sizes are so close that the difference, whatever it is, is within the error bars of measurement. That information comes only from data gathered in 2010. We simply do not know, at this point, which is larger.
The Pluto stuff is foolish showmanship, no doubt about it. I doubt that his book qualifies as garbage
However,

My allegations of shenanigans, moreover, are water-tight. The vote was hopelessly tainted.

indicates an astounding willingness to ignore the facts and history of the vote.,

The fact is there are numerous accounts of shenanigans. I'm not just making these accounts up. See Kornfeld posts and take it up with her. Brown should correct the book reviewers and make sure Chad and David get their credit. To not do so is contemptible in the extreme. All 3 are credited on Wikipedia. The book came out and reviews were published long after Eris was downsized. Sicardy's paper has Pluto as at least 12 km larger than Eris. Mass is a secondary matter. Size matters more. Ask any woman. If not garbage, flotsam and jetsam.

When I watched video of the infamous session, I saw a few shenanigans, too. When you are in a position of power and cut someone off in mid-sentence, that qualifies as a shenanigan.

"Notice, also, that initially it was believed that Eris was larger than Pluto. "

And notice that Pluto was supposed to be a damn sight bigger.

"I could care less about your blather about brown dwarfs."

So how much less? A bit? A lot?

Moreover, when you're wibbling on insanely about "dwarf stars are stars" and brown dwarfs are *failed* stars, then brown dwarfs is rather pertinent.

It seems that you will only every deign to note or care for things that support your victimisation seeking.

"When you are in a position of power and cut someone off in mid-sentence"

Someone has never had responsibility for being the chair of a meeting.

Along with many adherents of a geophysical planet definition, I do not hold the view that a celestial object has to clear its orbit or even dominate its orbit to be considered a planet. Planet is a broad term referring to non-self-luminous bodies in hydrostatic equilibrium, of which there are many subtypes, including some that don't orbit any star.

There should be a streamlining of terminology in astronomy. The term dwarf is used as an adjective modifying a noun in the cases of both galaxies and stars. In the same way, it should be used as an adjective modifying a noun in the case of planets. Dwarf planets are a subclass of planets the same way dwarf stars are a subclass of stars, and dwarf galaxies are a subclass of galaxies. Brown dwarfs are really brown dwarf stars, the low end of the stellar category. They may be failed stars, but at some point, even if it was brief, fusion of hydrogen or deuterium took place in their interiors.

The person who was strong armed into voting for resolution 5b was a graduate student at the time. It is well known that the academic world has its own issues of politics and bureaucracy. It is unfortunate, but graduate students, post-docs, and even professors who dissent with those in positions of power often are blacklisted and not hired for full time positions and/or not given funding for their projects. This is nothing new.

Some planets clear their orbits while others do not. According to the geophysical planet definition, not clearing or dominating its orbit does not preclude an object t from being a planet it just places the object in a different subclass of planets. And the fact that Earth would not clear its orbit if put in Pluto's location was mathematically determined by a dynamicist who supports the IAU definition, Dr. Hal Levison.

Many exoplanets do not clear or gravitationally dominate their orbits either, and most of these are giant planets, not small ones. In one case, a giant planet has such an eccentric orbit that it plunges through a belt of asteroids twice in its long orbit around its parent star. This planet and a good many exoplanets would never qualify as planets according to the IAU definition--even if the "requirement" to orbit the Sun was changed to a requirement to orbit a star.

Pluto is a part of more than one population. It's not an either/or. It is part of the planet population because it is a complex world with geology and weather that is massive enough to be rounded by its own gravity. At the same time, it is the largest member of a population of much smaller trans-Neptunian objects (though the latter are mostly icy, and Pluto is estimated to be 70 percent rock). To overlook Pluto's planetary qualities and lump it solely with a group of tiny iceballs is misleading and bad science.

Pluto is not tidally locked with Neptune. It is tidally locked with Charon, its giant moon, with both orbiting a common barycenter outside of Pluto this is why some astronomers consider Pluto-Charon a binary planet system with four moons. Pluto's orbit is in a two to three resonance with Neptune, meaning Pluto orbits the Sun twice for every three times Neptune orbits the Sun. That is not the same thing as being tidally locked.

Earth and Pluto have far more similarities beyond their both orbiting the Sun. Both worlds are rocky both have geology and weather both are geologically differentiated into core, mantle, and crust both have nitrogen in their atmospheres, and both have big moons formed via giant impacts. In fact, Earth has a lot more in common with Pluto than it does with Jupiter, Saturn, Uranus, and Neptune.

Many professional astronomers are not members of the IAU, having chosen not to join. That does not make them any less credible. The IAU has about 10,000 members 2,500 attended the start of the 2006 General Assembly, and 424 remained for the vote. Most of those 424 were not experts in planetary science but in completely different areas of astronomy.

You said, "Weird. Ever think of doing that yourself?" Doing what?

This is not about a vote that didn't go someone's way. It is about a highly flawed definition recognized as such by many astronomers and the need to come up with something better that reflects the reality of what is really out there, and that is billions of planets.
At the Great Planet Debate, astronomers who were present in Prague reported personal experiences of the shenanigans Mike talks about. Most astronomers do not attend the entire two weeks of the General Assembly, and many had already made airline reservations they could not change without having to spend a lot more money. Of course, they had no way of knowing the IAU would violate its own bylaws and instead of voting on the definition put forward by its own committee, would vote on a hastily thrown together alternate resolution instead. That resolution was literally put together the night before the vote it was not debated for 10 days.

Wow. Now that's a good post. My only criticism is that the word "numbnuts" wasn't in it.


  • Saturn has been known since ancient times because it can be seen without advanced telescopes.
  • Four robotic spacecraft have visited Saturn, including Pioneer 11, Cassini, and Voyager 1 and 2.

The Cassini spacecraft took this picture of Saturn's rings. You can see the grey and tan colors.

This is a picture of Saturn and its moons Tethys and Dione. Voyager 1 took this picture as it passed by.

NASA's Cassini spacecraft went behind Saturn and took this picture in 2013. You can see seven of its moons and its inner rings. In the background you can also see Earth.

A portrait looking down on Saturn and its rings. This picture was made from images taken by NASA's Cassini spacecraft in 2013. It was put together by amateur image processor and Cassini fan Gordan Ugarkovic.


Successfully launched at 4:43 EDT on the morning of October 15, 1997, NASA's Cassini Mission to Saturn, is the most ambitious deep space mission ever. The Saturn Educator Guide enables this extraordinary mission to become a real-world motivational context for learning standards-based science in grades 5-8.

Overview of Guide Contents

Six standards-based, constructivist lessons.

Relevant connections to art, poetry and mythology.

Download the complete Saturn Educator Guide in one ZIP file by clicking below.

Lesson Descriptions

Lesson 1: The Saturn System (3 hrs)

Students learn the basic concept of a system and work with a scale model of the Saturn system. Math skills: using a scale model, measurement, computation, estimation, and number sense.

  • Unifying Concepts & Processes
    Systems, Order and Organization
  • Science as Inquiry
    Abilities Necessary to do Scientific Inquiry
  • Earth & Space Science
    Earth in the Solar System

Lesson 2: Saturn's Moons (3 hrs)

Students use data on the 18 moons known to be orbiting in the Saturn system to discover patterns and important relationships between physical quantities in a planet-moon system. Math skills: number sense, controlling variables, recognizing patterns, and measurement.

  • Unifying Concepts & Processes
    Systems, Order and Organization
  • Science as Inquiry
    Abilities Necessary to do Scientific Inquiry
  • Earth & Space Science
    Earth in the Solar System

Lesson 3: Moons, Rings, and Relationships (3-4 hrs)

Students explore the fundamental force of gravity and how it acts to keep objects like moons and ring particles in orbit. Math skills: measurement, number relationships, recognizing patterns, creating and interpreting graphs.

  • Science as Inquiry
    Abilities Necessary to do Scientific Inquiry
  • Physical Science
    Motions and Forces
  • Earth & Space Science
    Earth in the Solar System

Lesson 4: History of Saturn Discoveries (3 hrs)

Students examine how scientists throughout human history have learned about Saturn. They learn how scientific knowledge evolves and how technology has improved our ability to solve Saturn's mysteries. Math skills: number sense, measurement and scaling (creating a timeline).

  • History & Nature of Science
    Science as a Human Endeavor
    History of Science
  • Science & Technology
    Understandings about Science and Technology
  • Earth & Space Science
    Understandings about Science and Technology

Lesson 5: The Cassini Robot (3-4 hrs)

Students explore the capabilities of a robot like the Cassini spacecraft. They compare its robotic functions to human functions.

  • Unifying Concepts & Processes
    Form and Function
  • Science & Technology
    Abilities of Technological Design

Lesson 6: People of the Cassini Team (1.5-2 hrs)

Students use a diverse collection of profiles of people who work on the Cassini mission to learn about science as a human endeavor, and to reflect on their own career goals.

  • History & Nature of Science
    Science as a Human Endeavor
  • Science in Peronal & Social Perspectives
    Science and Technology in Society

Explore More!

For more information on the Cassini mission, visit the Cassini Web site. For more information and images of Saturn, check out JPL's Cassini Picture Archive.

About our museum

A visible trace, evidence, or sign of something that once existed but exists or appears no more: a building that is the area's last vestige of its colonial era. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla convallis egestas rhoncus. Donec facilisis fermentum sem, ac viverra ante luctus vel. Donec vel mauris quam.


Important Events:

  • 700 BCE: The Assyrians are credited for documenting the oldest written records on Saturn. Their description of Saturn calls it a sparkle in the night and they named it “Star of Ninib.”
  • 400 BCE: The Ancient Greeks gave the name of the planet as Kronos, to honor their god of agriculture. Later the Romans changed it to Saturn, which is their god of agriculture.
  • 1610: Galileo Galilei identifies Saturn’s rings through a telescope, but thinks they are a triple planet.
  • 1655: Christiaan Huygens discovers Saturn’s rings as well as its moon, Titan.
  • 1675: Astronomer Jean-Dominique Cassini discovers a “division” between our currently identified A and B rings.
  • 1979: Pioneer 11 becomes the first spacecraft to reach Saturn and discovers the F ring as well as another moon.
  • 1980 and 1981: Voyager 1 does a flyby of Saturn in 1980 and shows the structure of Saturn’s ring system which is made up of thousands of ringlets. The 1981 flyby of Voyager 2 includes a lot more detail of Saturn in images and data collected showed that some of the rings are very thin.
  • 2004: NASA’s Cassini spacecraft is the first to be devoted to a complete orbit of Saturn and devotes ten years to the study of Saturn, its rings, and its moons.
  • 2005: The ESA (European Space Agency’s) Huygens probe becomes the first to make a landing on the surface of another planet’s moon, Titan. The probe sent information on Titan’s atmosphere and images of the surface.
  • 2006: Scientists discover a new ring around Saturn.
  • 2009: NASA’s Spitzer Space Telescope sends data that shows that there is a large, low density ring associated with Saturn’s moon Phoebe.
  • 2017: Cassini’s mission in orbit ends the 13 year study by sending the spacecraft into the atmosphere of Saturn while it collected and sent back data.

Was Phosphine on Venus Just Sulfur Dioxide?

In September 2020, a group of astronomers reported finding phosphine – a chemical normally associated with life – in the clouds of Venus. Now, a new study shows this finding may have been in error. This new study suggests sulphur dioxide – a chemical that makes up the smell of burned matches – may have been responsible for the earlier finding, dashing hopes for finding primitive life in the clouds of our planetary neighbor.

Upcoming Guests

June 29 (s4/e26): Alyssa Mills, Graduate intern at JPL, talks about the largest moon in the Solar System, Ganymede.

July 6 (s5/e1): SEASON FIVE PREMERE! New York Times bestselling author Earl Swift, author of Across the Airless Wilds, the first major history of NASA’s lunar buggy.

July 13 (s5/e2):

Stella Kafka, CEO of The American Association of Variable Star Observers, talking about Betelgeuse.

July 20 (s5/e3):

Geoff Notkin, host of Meteorite Men on the Science Channel and president of the National Space Society, talks meteorites.

July 27 (s5/e4):

CHIME member Kaitlyn Shin, MIT grad student, explains fast radio bursts (FRBs)

August 3 (s5/e5):

Teaching science to children with Stephanie Ryan, author of “Let’s Learn Chemistry.”

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Appreciation

“Nobody doesn’t love astronomy out there, and you’re in the middle of that, so keep that going.” – Neil deGrasse Tyson

“The show is a great way to keep up with new discoveries in space sciences. One gets to directly hear from scientists in an easy to understand language.”- Dr. Dimitra Atri, NYU Abu Dhabi

“Your site is great, and I think your videos are wonderful.” – Dr. Jack Hughes, Rutgers University


Outer Planets Could Warm Up as Sun Dies

Image credit: NASA
We are doomed. One day the Earth will be a burnt cinder orbiting a swollen red star.

This is the ultimate fate of any planet living close to a main sequence star like our sun. Main sequence stars run on hydrogen, and when this fuel runs out, they switch over to helium and become a red giant. While the sun’s transition into a red giant is sad news for Earth, the icy planets in the most distant regions of our solar system will bask in the sun’s warmth for the first time.

The sun has been slowly but steadily growing brighter and hotter over the course of its lifetime. When the sun becomes a red giant in about 4 billion years, our familiar yellow sun will turn a vivid red, as it mainly emits the lower frequency energy of infrared and visible red light. It will grow thousands of times brighter and yet have a cooler surface temperature, and its atmosphere will expand, slowly engulfing Mercury, Venus and possibly even the Earth.

While the sun’s atmosphere is predicted to reach Earth’s orbit of 1 AU, red giants tend to lose a lot of mass, and this wave of expelled gases could push Earth just out of range. But whether the Earth is consumed or merely singed, all life on Earth will have passed into oblivion.

Yet the conditions that make life possible could appear elsewhere in the solar system, according to a paper published in the journal Astrobiology by S. Alan Stern, Director of the Southwest Research Institute’s Department of Space Studies in Boulder, Colorado. He says that planets located 10 to 50 AU will be in the red giant sun’s habitable zone. The habitable zone of a solar system is the region where water can remain in a liquid state.

The habitable zone will shift gradually through the 10 to 50 AU region as the sun grows brighter and brighter, evolving through its red giant phase. Saturn, Uranus, Neptune and Pluto all lie within 10 to 50 AU, as do their icy moons and the Kuiper Belt Objects. But not all these worlds will have an equal chance at life.

The prospects for habitability on the gaseous planets Saturn, Neptune and Uranus may not be affected all that much by the red giant transition. Astronomers have discovered gaseous planets orbiting very close to their parent star in other solar systems, and these “hot Jupiters” seem to hold onto their gaseous atmospheres despite their proximity to the intense radiation. Life as we know it is not likely to appear on gaseous planets.

Stern thinks Neptune’s moon Triton, Pluto and its moon Charon, and the Kuiper Belt Objects will have the best chances for life. These bodies are rich in organic chemicals, and the heat of the red giant sun will melt their icy surfaces into oceans.

“When the sun is a red giant, the ice worlds of our solar system will melt and become ocean oases for tens to several hundreds of millions of years,” says Stern. “Our solar system will then harbor not one world with surface oceans, as it does now, but hundreds, for all of the icy moons of the giant planets, and the icy dwarf planets of the Kuiper Belt will also bear oceans then. Because temperature on Pluto will not be very different then, than Miami Beach’s temperature now, I like to call these worlds ‘warm Plutos,’ in analogy to the plethora of hot Jupiters found orbiting sun-like stars in recent years.”

The influence of the sun is not the whole story, however – the characteristics of a planetary body go a long way toward determining habitability. Such characteristics include a planet’s internal activity, the reflectivity, or “albedo” of a planet, and the thickness and composition of the atmosphere. Even if a planet has all the elements that favor habitability, life will not necessarily appear.

“We don’t know what is needed to start life,” says Don Brownlee, an astronomer with the University of Washington in Seattle and co-author of the book, “The Life and Death of Planet Earth.” Brownlee says that if warm wet interiors and organic materials are all that’s needed, then Pluto, Triton, and the Kuiper Belt Objects could harbor life.

“As a word of caution, however, the interiors of asteroids that produced the carbonaceous chondrite meteorites were warm and wet for perhaps millions of years in the early history of the solar system,” says Brownlee. “These bodies are extremely rich in both water and organic materials, and yet there is no compelling evidence that any asteroidal meteorite ever had living things in it.”

A planetary body’s orbit also will affect its chances for life. Pluto, for instance, doesn’t have a nice, regular orbit like the Earth. The orbit of Pluto is comparatively eccentric, varying in distance from the sun. From January 1979 through February 1999, Pluto was closer to the sun than Neptune, and in a hundred years, it’ll be almost twice as far out as Neptune. This type of orbit will cause Pluto to undergo extreme heating alternating with extreme cooling.

Triton’s orbit, too, is peculiar. Triton is the only large moon to orbit backwards, or “retrograde.” Triton may have this unusual orbit because it formed as a Kuiper Belt Object and then was captured by Neptune’s gravity. It’s an unstable alliance, since the retrograde orbit creates tidal interactions with Neptune. Scientists predict that someday Triton will either crash into Neptune, or break up into tiny pieces and form a ring around the planet.

“The timescale for the tidal decay of Triton’s orbit is uncertain, so it could be around, or it might have already crashed by the time the sun goes red giant,” says Stern. “If Triton is around, it’ll probably end up looking like the same kind of organic-rich ocean world as Pluto.”

The sun will burn as a red giant for about 250 million years, but is that enough time for life to get a foothold? During most of the red giant lifetime, the sun will be only 30 times brighter than its current state. Toward the end of the red giant phase the sun will grow more than 1,000 times brighter, and occasionally release pulses of energy reaching 6,000 times current brightness. But this period of intense brightness will last for a few million years, or tens of millions of years at most.

The brevity of the red giant’s brightest phases suggests to Brownlee that Pluto doesn’t hold much promise for life. Because of Pluto’s average orbit of 40 AU, the sun would have to be 1,600 times brighter for Pluto to get the same solar radiation we currently get on Earth.

“The sun will reach this brightness, but only for a very brief period of time – only a million years or so,” says Brownlee. “The surface and atmosphere of Pluto will be ‘improved’ from our point of view, but it won’t be a nice place for any significant period of time”.

After the red giant phase, the sun will become fainter, and will shrink to the size of the Earth, becoming a white dwarf. The distant planets that basked in the light of the red giant will become frozen ice worlds once again.

So if life is to appear in a red giant system, it will need a quick start. Life on Earth is thought to have originated 3.8 billion years ago, some 800 million years after our planet was born. But that is probably because the planets in the inner solar system experienced 800 million years of heavy asteroid bombardment. Even if life had gotten started immediately, the early rain of asteroids would’ve wiped the Earth clean of that life.

Brownlee says a new era of bombardment could begin for the outer planets, because the red giant sun could disturb the vast number of comets in the Kuiper Belt.

“When the red giant sun is 1,000 times brighter, it loses almost half of its mass to space,” says Brownlee. “This causes orbiting bodies to move outward. Gas loss and other effects might destabilize the Kuiper Belt and create another period of interesting bombardment.”

But Stern says that planets made habitable by a red giant sun won’t be bombarded as often as the early Earth was, because the ancient asteroid belt had much more material than the Kuiper Belt has today.

In addition, the outer planets won’t experience the same ultraviolet (UV) levels that Earth has had to endure, since red giants have very low UV radiation. The higher intensity UV of a main sequence star can be damaging to the delicate proteins and RNA strands needed for life’s origin. Life on Earth could only originate underwater, in depths protected from this light intensity. Life on Earth is therefore inextricably linked to liquid water. But who knows what sort of life might originate on planets that have no need for UV shielding?

Stern thinks we should look for evidence of life on Pluto-like worlds orbiting around red giants today. We currently know of 100 million solar-type stars in the Milky Way galaxy that burn as red giants, and Stern says that all of these systems could have habitable planets within 10 to 50 AU. “It would be a good test of the time required to create life on warm, water-rich worlds,” he says.

“The idea of organic-rich distant bodies getting baked by a red giant star is an intriguing one, and could provide very interesting if short-lived habitats for life,” adds Brownlee. “But I am glad that our sun has a good margin of time left.”

What’s Next
While much of what we know about the outer solar system is based on distant measurements made from Earth-based telescopes, on January 2, 2004, scientists caught a close-up glimpse of a Kuiper Belt Object. The Stardust spacecraft passed within 136 kilometers of comet Wild2, an enormous snowball that spent most of its 4.6 billion-year lifetime orbiting in the Kuiper Belt. Wild2 now orbits mostly inside the orbit of Jupiter. Brownlee, who is the Principle Investigator for the Stardust mission, says that the Stardust images show fantastic surface details of a body shaped both by its ancient and recent history. Stardust images show gas and dust jets shooting off the comet, as Wild2 rapidly disintegrates in the strong solar heat of the inner solar system.

To learn more about the outer solar system, we’ll need to send a spacecraft out there to investigate. In 2001, NASA selected the New Horizons mission for just such a purpose.

Stern, who is the Principal Investigator for the New Horizons mission, reports that the spacecraft assembly is scheduled to begin this summer. The spacecraft is due to launch in January 2006, and arrive at Pluto the summer of 2015.

The New Horizons mission will allow scientists to study the geology of Pluto and Charon, map their surfaces, and take their temperatures. Pluto’s atmosphere also will be studied in detail. In addition, the spacecraft will visit the icy bodies in the Kuiper Belt in order to make similar measurements.


Watch the video: 10 Fakten über Nereid (January 2023).