Astronomy

In a planetary system close to the galactic core, would it be possible to see the supermassive black hole?

In a planetary system close to the galactic core, would it be possible to see the supermassive black hole?


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I understand that radiation on planets near the galaxy's center make life on these planets nearly impossible, and that one cannot truly “see” a black hole. However, if you could stand on the surface of a planet that orbits a star close to or within the galactic core, could you theoretically look up at the sky and see an absence of light/stars indicating the location of the central supermassive black hole?

Would it be too far away to see, obstructed by debris, or too small to notice?


You couldn't see it as a black patch in the sky, because it's far too small. It's only 17 times the radius of our sun, which of course you can't see as a disc even from the outer reaches of our own solar system. What you could easily see is the much larger area of light and other radiation from matter falling into it.


If the black hole is active, meaning it is still capturing matter from its surrounding, it will have a large accretion disk all around, which is the only way to dissipate angular momentum for the matter falling into it.

As a result of this dissipation all the matter will warm up and emit radiation. This disc will be fairly large and thus clearly visible as a bright object in the sky.

This page shows an image captured by Hubble of such a disk:

Strictly speaking then, one cannot see directly the black hole, as its view will be covered by the bright emission of the disk.

However, the presence of the disk will allow to observe the black hole thanks to its gravitational effect.


There's a thing called gravitational lensing, which means that light coming from behind the black hole would bend towards it, and since the galactic core has a lot of stars, it might be that instead of a black spot in the sky, you'd see a great accumulation of light in and around the black hole's position.

I'm not sure how literal "lensing" is, so I don't know whether there is a focal point based on gravity and the energy of the light and whether it would matter where the planet is from this focal point.

http://www.cfhtlens.org/public/what-gravitational-lensing (google will provide more links if you search for it)


Rainbow cloud.

A source of radiation from black holes is stuff spiralling into the black hole, heating up as it "fell" and released its gravitational potential energy. Again this is black body radiation but this time the regular kind: the hotter the emitters are is the shorter the wavelength. This radiation comes from next to the black hole, not out of the hole itself.

https://physics.stackexchange.com/questions/24958/how-can-a-black-hole-emit-x-rays

The X-rays come from hot gas orbiting around the black hole in an accretion disk. As the gas orbits, magnetic stresses cause it to lose energy and angular momentum, thus spiralling slowly in towards the black hole. The orbital energy is transformed into thermal energy, heating up the gas to millions of degrees, so it then emits blackbody radiation in the X-ray band.

Once the gas gets closer than a few times the horizon radius, it plunges into the black hole, so while some X-rays can still escape just before the horizon, most are emitted a fair bit outside.

Telescopes to detect black holes look for the most energetic rays, which are emitted from the hottest areas of gas nearest the hole. We cannot stand on a planet and look up and see xrays. But consider: if there is very hot gas, next to it there is less hot gas, and next to that gas that is less less hot. The cooler a blackbody is, the longer wavelength the emitted radiation is. Somewhere in that progressively cooler cloud is gas which emits radiation in the visible wavelength.

I here assert that the gradual change in temperature of this cloud as it is progressively farther from the hottest innermost gas should produce a gradual change in the frequencies emitted. The first visible light would be in the far violet, nearest the hole. This will grade through blues and greens farther away and then to red at the farthest coolest part of the cloud.

This prediction should be true not just for black holes, but for any cloud of gas heated from within. Now let me look… here we go.

https://www.space.com/12051-bright-nebula-photo-supergiant-star-betelgeuse.html

The black hole rainbow cloud will be more symmetric than this one. The star is spewing this stuff out willy-nilly but the hole is sucking gas in, so it will be a symmetric spiral.



A “Cosmic Microscope” Reveals The Origin Of Galactic Winds Produced By Supermassive Black Holes (Astronomy / Cosmology)

By studying a sample of distant galaxies, whose light reaches us from a cosmic epoch when the Universe was just three billion years old, a team of researchers led by Giustina Vietri of the Italian National Institute for Astrophysics (INAF) has followed the winds blowing in “active” galaxies down to only a few light-years from the supermassive black holes that sit in the galactic cores. The new study demonstrates how these winds, which travel as fast as millions of kilometres per hour, have the potential to influence interstellar gas on scales of tens of thousands light-years.

Dust torus around SMBH © ESA / Hubble

The majority of supermassive black holes lurking in galaxies, like the one at the centre of our own Milky Way, are harmless and swallow at most the occasional star or gas cloud that dare venture too close. A small percentage, however, is in great turmoil, devouring the surrounding matter at high pace via an accretion disc that heats up and emits radiation across the electromagnetic spectrum. It is from these signals that it is possible to recognise “active” galaxies, hosting such frenzied black holes, in astronomical observations.

Not even the most “voracious” black holes, however, are capable of eating all the material in their surroundings, triggering enormous winds that throw away part of this material and can propagate over galactic scales. Astrophysicists have been debating for years about the importance of such winds and their possible effects on the evolution of the host galaxies via feedback mechanisms, which might have the potential to regulate both the growth of the central black hole and the formation of new stars.

“It’s a topic of great importance to understand how the Universe has evolved”, comments Giustina Vietri from INAF in Milan, first author of a new study analysing the effect of such winds on different scales within galaxies, for the first time using a representative sample of active galaxies. “In this study we tried to shed new light on one of the currently most debated issues: the link between the central supermassive black holes and their host galaxies”.

The results, published in Astronomy & Astrophysics, are part of the SUPER project (A SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback), which has already produced two papers authored by the same team of researchers. The project was created with the aim of studying the release of gas from galactic centres using the SINFONI instrument on ESO’s Very Large Telescope, in Chile.

“SINFONI is an integral-field spectrograph operating in the near-infrared and exploiting adaptive optics to gather high-resolution spectra of extended sources”, explains Vincenzo Mainieri from ESO, principal investigator of the SUPER project and co-author of the new study. “With respect to previous instruments used for spectroscopic surveys of active galaxies, SINFONI enables us to spatially resolve the gas”.

Thanks to the data obtained with SINFONI, the team has analysed a representative sample of 21 active galaxies, studying the connection between black holes and their host galaxies, for the first time, in a systematic fashion. This means they did not have to select galaxies where the presence of winds was already known. The observations have revealed the presence of galactic winds in all examined sources. The result demonstrates how prevalent these phenomena are in the cosmic epoch to which these galaxies belong, when our 13.8 billion-year old Universe was only 3 billion years of age.

“These winds, travelling at speeds between 3 and 7 million km/h, reach out to twenty thousand light-years from the centre of their host galaxies”, adds co-author Michele Perna from INAF in Florence and Centro de Astrobiología in Madrid, Spain.

The researchers then followed the winds all the way to their origin, in the vicinity of the monster black holes, by making use of an astronomical “microscope” – analysing optical spectra of these galaxies available from the archives.

“The lines emitted by ionised carbon atoms, which we see in spectra from the Sloan Digital Sky Survey, are produced only a few light-years away from the black hole, revealing how the winds of ionised material discovered with SINFONI are also present on these relatively small scales, in the heart of galaxies”, explains Vietri. “By doing so, we could link for the first time the presence of outflows from the proximity of the black hole to galaxy scales”.

The results show how the winds observed at small distances from the central black hole depend on its properties – such as the accretion rate or the brightness of the galactic core, which is in turn produced by the black hole’s activity. Furthermore, these winds might have the potential to influence gas all the way to the outskirts of their host galaxies. In the future, the researchers will try to trace these winds on even larger scales to keep studying the influence that black holes may exert on the evolution of galaxies.

The study is published in Astronomy & Astrophysics in the paper “SUPER III. Broad Line Region properties of AGN at z∼2” by G. Vietri, V. Mainieri, D. Kakkad, H. Netzer, M. Perna, C. Circosta, C. M. Harrison, L. Zappacosta, B. Husemann, P. Padovani, M. Bischetti, A. Bongiorno, M. Brusa, S. Carniani, C. Cicone, A. Comastri, G. Cresci, C. Feruglio, F. Fiore, G. Lanzuisi, F. Mannucci, A. Marconi, E. Piconcelli, A. Puglisi, M. Salvato, M. Schramm, A. Schulze, J. Scholtz, C. Vignali, G. Zamorani.


Gravitational wave kicks monster black hole out of galactic core

Astronomers have uncovered a supermassive black hole that has been propelled out of the center of a distant galaxy by what could be the awesome power of gravitational waves.

Though there have been several other suspected, similarly booted black holes elsewhere, none has been confirmed so far. Astronomers think this object, detected by NASA's Hubble Space Telescope, is a very strong case. Weighing more than 1 billion suns, the rogue black hole is the most massive black hole ever detected to have been kicked out of its central home.

Researchers estimate that it took the equivalent energy of 100 million supernovas exploding simultaneously to jettison the black hole. The most plausible explanation for this propulsive energy is that the monster object was given a kick by gravitational waves unleashed by the merger of two hefty black holes at the center of the host galaxy.

First predicted by Albert Einstein, gravitational waves are ripples in space that are created when two massive objects collide. The ripples are similar to the concentric circles produced when a hefty rock is thrown into a pond. Last year, the Laser Interferometer Gravitational-Wave Observatory (LIGO) helped astronomers prove that gravitational waves exist by detecting them emanating from the union of two stellar-mass black holes, which are several times more massive than the sun.

Hubble's observations of the wayward black hole surprised the research team. "When I first saw this, I thought we were seeing something very peculiar," said team leader Marco Chiaberge of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, Maryland. "When we combined observations from Hubble, the Chandra X-ray Observatory, and the Sloan Digital Sky Survey, it all pointed towards the same scenario. The amount of data we collected, from X-rays to ultraviolet to near-infrared light, is definitely larger than for any of the other candidate rogue black holes."

Chiaberge's paper will appear in the March 30 issue of Astronomy & Astrophysics.

Hubble images taken in visible and near-infrared light provided the first clue that the galaxy was unusual. The images revealed a bright quasar, the energetic signature of a black hole, residing far from the galactic core. Black holes cannot be observed directly, but they are the energy source at the heart of quasars - intense, compact gushers of radiation that can outshine an entire galaxy. The quasar, named 3C 186, and its host galaxy reside 8 billion light-years away in a galaxy cluster. The team discovered the galaxy's peculiar features while conducting a Hubble survey of distant galaxies unleashing powerful blasts of radiation in the throes of galaxy mergers.

"I was anticipating seeing a lot of merging galaxies, and I was expecting to see messy host galaxies around the quasars, but I wasn't really expecting to see a quasar that was clearly offset from the core of a regularly shaped galaxy," Chiaberge recalled. "Black holes reside in the center of galaxies, so it's unusual to see a quasar not in the center."

The team calculated the black hole's distance from the core by comparing the distribution of starlight in the host galaxy with that of a normal elliptical galaxy from a computer model. The black hole had traveled more than 35,000 light-years from the center, which is more than the distance between the sun and the center of the Milky Way.

Based on spectroscopic observations taken by Hubble and the Sloan survey, the researchers estimated the black hole's mass and measured the speed of gas trapped near the behemoth object. Spectroscopy divides light into its component colors, which can be used to measure velocities in space. "To our surprise, we discovered that the gas around the black hole was flying away from the galaxy's center at 4.7 million miles an hour," said team member Justin Ely of STScI. This measurement is also a gauge of the black hole's velocity, because the gas is gravitationally locked to the monster object.

The astronomers calculated that the black hole is moving so fast it would travel from Earth to the moon in three minutes. That's fast enough for the black hole to escape the galaxy in 20 million years and roam through the universe forever.

The Hubble image revealed an interesting clue that helped explain the black hole's wayward location. The host galaxy has faint arc-shaped features called tidal tails, produced by a gravitational tug between two colliding galaxies. This evidence suggests a possible union between the 3C 186 system and another galaxy, each with central, massive black holes that may have eventually merged.

Based on this visible evidence, along with theoretical work, the researchers developed a scenario to describe how the behemoth black hole could be expelled from its central home. According to their theory, two galaxies merge, and their black holes settle into the center of the newly formed elliptical galaxy. As the black holes whirl around each other, gravity waves are flung out like water from a lawn sprinkler. The hefty objects move closer to each other over time as they radiate away gravitational energy. If the two black holes do not have the same mass and rotation rate, they emit gravitational waves more strongly along one direction. When the two black holes collide, they stop producing gravitational waves. The newly merged black hole then recoils in the opposite direction of the strongest gravitational waves and shoots off like a rocket.

The researchers are lucky to have caught this unique event because not every black-hole merger produces imbalanced gravitational waves that propel a black hole in the opposite direction. "This asymmetry depends on properties such as the mass and the relative orientation of the back holes' rotation axes before the merger," said team member Colin Norman of STScI and Johns Hopkins University. "That's why these objects are so rare."

An alternative explanation for the offset quasar, although unlikely, proposes that the bright object does not reside within the galaxy. Instead, the quasar is located behind the galaxy, but the Hubble image gives the illusion that it is at the same distance as the galaxy. If this were the case, the researchers should have detected a galaxy in the background hosting the quasar.

If the researchers' interpretation is correct, the observations may provide strong evidence that supermassive black holes can actually merge. Astronomers have evidence of black-hole collisions for stellar-mass black holes, but the process regulating supermassive black holes is more complex and not completely understood.

The team hopes to use Hubble again, in combination with the Atacama Large Millimeter/submillimeter Array (ALMA) and other facilities, to more accurately measure the speed of the black hole and its gas disk, which may yield more insight into the nature of this bizarre object.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.


Planets hurtling near the speed of light? It's possible, study says.

Scientists want to know if planets can form near the supermassive black hole at the core of the galaxy. If so, the black hole could fling them out into space at enormous speeds that, from our vantage point, could appear to approach the speed of light.

Deep in the heart of the Milky Way, where a supermassive black hole lurks, conditions are so chaotic that planets – and perhaps life – can't form: Or can they?

A small team of astronomers suggests one way to answer the question, at least as it relates to planets: Monitor the Milky Way's rejects – stars that the galaxy's central black hole has kicked toward intergalactic space – for signs of planets.

Such planets – orbiting a star or traveling alone – so far are hypothetical. The center of the galaxy is so shrouded in dust that planet-hunting as it's practiced in our galactic neighborhood is futile.

But individual ejected stars, dubbed hypervelocity stars because they are ejected at such great speeds, are anything but hypothetical. The first stellar speedster was reported to be leaving the galaxy in 2005. Since then, the total has grown to at least 16 hypervelocity stars reported.

Hunting for more in the galaxy's halo, where they are most obvious, then monitoring them for the signature of a planet's transit across the star's face, would help settle the question of whether the center of the galaxy is hospitable for planet formation, explains Avi Loeb, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

As Kamala Harris’ portfolio grows, so does the scrutiny

He is one of the co-authors of a paper set for publication in the Monthly Notices of the Royal Astronomical Society in Britain that looks at the ejection mechanism and how one might go about the hunt.

With planet-hunting efforts such as NASA's Kepler mission finding hundreds of confirmed planets, with at least 2,000 candidates waiting in the wings for confirmation, the notion that stars at the galactic center also host planets would seem reasonable.

But several factors could weigh against planet-making there, Dr. Loeb explains.

The broader region around the black hole is a hotbed of star formation. Stars are roughly a million times more densely packed there than the stars in the sun's neighborhood. At the galactic center, the stars that form generally are more massive than the sun, burn hotter, and flit about the galactic center at speeds of more than 2 million miles an hour, compared with roughly half a million miles an hour for the sun.

Under those cramped, turbulent conditions, it would be hard for a star's disk of dust and gas to hang together long enough to allow planets form.

Still some observations hint that planets might form close to the Milky Way's center.

For instance, researchers have noted intriguing flare-like events as material gets heated, compressed, then swallowed via the black hole's extraordinary gravitational tug. Evidence suggests that the material might not be a star but asteroids – planetary building blocks.

The thinking: A flare from a doomed sun-like star would happen about once every 10,000 years and last for months, noted a team of astronomers from the University of Leicester in Britain and the University of Amsterdam in the Netherlands last fall. But observers had detected daily flares that would last for a few hours.

Earlier this year, researchers discovered what they interpreted as a gas cloud falling into the black hole. One possible explanation: The cloud originally orbited a low-mass star, but got yanked free to feed the black hole. The presence of a gas cloud near the galactic core would also suggest that planetary building-blocks exist there.

But what would happen to planetary systems after a close encounter with a supermassive black hole?

Loeb and collegues considered planets orbiting binary stars at a distance of 2,000 Astronomical Units from the galaxy's central black hole – or about 2,000 times the distance from Earth to the sun. If the stars contained one or two Jupiter-scale planets each, gravitational interactions between the stars and the black hole could send one star and its offspring hurtling out of the galaxy.

The remaining star would be stripped of its planets, which also could be ejected. Under the right conditions, the team calculated, these starless planets could leave the galaxy at a speed a few percent of the speed of light. Meanwhile, the now-planetless star left behind would migrate closer to the black hole.

“Other than subatomic particles, I don't know of anything leaving our galaxy as fast” as the fastest runaway planets in the team's simulations, said Idan Ginsburg, a graduate student at Dartmouth College in Hanover, N.H., and the new paper's lead author, in a prepared statement.

For a planet to remain bound to an ejected star, it would have to be orbiting very close to the star, Loeb says. That also would significantly boost the chance that big, ground-based telescopes could spot the effect these planets would have on the star's light as they transit their sun.

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If hypervelocity planets or planetary systems exist, and if they harbored life sentient enough to notice, “this ride would be quite exciting,” Loeb says.

A planet system would move slower than an unbound planet, but in principle it could still be in for the ride of its life, he adds. It could get swept up into the accelerating expansion of space itself, he speculates, eventually reaching velocities that from an Earth-bound vantage point would appear to approach the speed of light.


Planets around Supermassive Black Holes are now possible, research reveals

Seen nearly edgewise, the turbulent disk of gas churning around a black hole takes on a crazy double-humped appearance. The black hole’s extreme gravity alters the paths of light coming from different parts of the disk, producing the warped image. The black hole’s extreme gravitational field redirects and distorts light coming from different parts of the disk, but exactly what we see depends on our viewing angle. The greatest distortion occurs when viewing the system nearly edgewise. Above image is a NASA simulation of how a Black Hole might look like.

Credit: NASA’s Goddard Space Flight Center/Jeremy Schnittman

Every galaxy has its heart in the epicenter, and as your human heart, this heart is also vital to the galaxy it exists in. A supermassive black hole is what this organ is in terms of space and science. In the case of our Milky Way, the location of this Black Hole is at the Galactic Core, the rotational center of our galaxy, or the site of the Saggitarius A, a compact astronomical radio source.

Before we jump into knowing more about the planets around a black hole, we need to know what a Black Hole is exactly. It is a region of space-time where the power of gravity is so strong that even light can’t escape from it. After being formed, a black hole absorbs anything that crosses a specific boundary, also known as the event horizon. Each black hole has a doughnut-shaped formation of dust and gases around it, which is called a torus.

The various aspects of the simulation. Image Source: NASA’s Goddard Space Flight Center/Jeremy Schnittman

By absorbing other stars and mixing up with other black holes, we get what is known as a supermassive black hole. A supermassive black hole can have a mass four million times the mass of the sun sitting at the center of our solar system.

But according to the latest research by the National Astronomical Observatory of Japan, it may be possible for planets to orbit them.

Earlier, we had the notion that planets only formed from protoplanetary disks, which were made up of dust and gas found around stars. But this latest research states that planets may also develop from the torus around an SMBH (Supermassive Black Hole).

An artistic rendering of a supermassive black hole. Image: NASA

“The torus of an SMBH has a mass of about 100,000 times the mass of the sun, which is a billion times the mass of the dust in a protoplanetary disk,” says Professor Eiichiro Kokubo and colleagues from the National Astronomical Observatory of Japan in a statement. For the dust in a torus to form a planet, we need different temperatures in the clouds (which is where the black holes play a part). The dust disk around the black holes is so intense that the strong radiation from the central region is stopped and the low-temperature areas are formed.

If the temperature is low enough, the dust can cluster together to form a protoplanet, which is a primary stage in the building of a planet. Small icy particles can be formed from these regions, which can eventually grow into Earth-sized worlds. The distance from the black holes can be as close as just ten light-years away from the black hole with the planet being ten times the mass of our planet Earth.

This can lead to a planetary system around the black holes. This is an astounding find when taken into the fact that the conditions there are very harsh and raspy. The team’s paper is going to be published in the Astrophysics Journal.

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New Observations Confirm the Galactic Superwave Theory

It took over 30 years to confirm a key thesis of the galactic superwave theory, but now incontrovertible evidence has been found. Observations of the active galaxy PDS 456 made with NASA’s NuSTAR space telescope (Nuclear Spectroscopic Telescope Array), in operation since June 2012, and with the European Space Agency’s XMM-Newton space telescope, now show the presence of an extremely high velocity wind moving outward isotropically away from the galaxy’s center in all directions at up to 30% of the speed of light. Prior to this astronomers had assumed that the winds produced by active galactic cores issued primarily from their poles in the form of jets.

In my 1983 Ph.D. dissertation, I had argued against this model showing evidence that cosmic rays from active galactic cores (quasars, blazers, Seyfert galaxies, etc.) radiate in all directions, not just toward the poles and that the forward beaming of synchrotron radiation from ultra relativistic cosmic rays gives the illusion that they are confined as jets because due to beaming the cosmic rays coming almost directly toward us are the only ones whose radiation we are able to see. The misinterpretation by the astronomical community that the jet phenomenon is being produced by cosmic rays moving outward slowly in the form of a magnetized plasma had misled the astronomical community for years into thinking that jets are aligned almost perpendicular to our line of sight and that their cosmic rays and gas escape mainly from a galaxy’s poles. The conventional theory had gas motion in the galaxy’s disc moving primarily inward toward its center to feed its supermassive core (mistakenly construed to be a “black hole”). I have been challenging this model for 32 years, in my dissertation, in the 1987 journal paper: Cosmic ray volleys from the Galactic Center and their recent impact on the earth environment, in the book Earth Under Fire, and in various web postings:
• https://starburstfound.org/superwaveblog/?p=334
• https://starburstfound.org/superwaveblog/?p=195
• https://starburstfound.org/superwaveblog/?p=16
• https://etheric.com/fermi-gamma-ray-evidence-superwaves-traveling-outward-galactic-center/
• https://etheric.com/msnbc-interviews-paul-laviolette/

PDS 456 is an active galaxy over 2 billion light years away (z = 0.18) whose core is going through a quasar phase emitting radiation at the rate of

10 47 ergs per second, a rate about 100 trillion times greater than our own galactic core. Using these new telescopes, astronomers were able to spectroscopically detect the emission and absorption features of high velocity iron atoms streaming away from its Galactic center along with other ionized gas. They discovered that these spectroscopic features matched what astronomers call a P Cygni profile, a spectroscopic blueshift/redshift signature produced by ionized gas streaming outwards in all directions in the form of a sphere or spherical shell. They observed the wind at around 700 AU from the Galactic core (

700 times the Sun-to-Earth distance) and observed that it spread outward over a solid angle of at least 2π, hence over at least half of the surface of the sphere, with the implication that it actually blew outward in all directions.

Quite likely they will be finding similar spherical wind outflows in other galaxies as well. This finding challenges the conventional view that these supermassive black holes are cores energized by in falling material. Because this group acknowledges that with a wind as strong as they are seeing (10 46 erg/second) it would be impossible for material to fall into the core to fuel its observed emission. Black hole theorists side step this by suggesting that the “black hole’s” activity was fired up at an earlier date when such a wind was absent and that now the presence of this wind will have a limiting effect to cause the black hole’s activity to shut off. Such reasoning, in my opinion, is pure fantasy. The high velocity wind is there because the core is active, and the core is active not because material is falling into it, but because of its intrinsic energy production through spontaneous energy creation, the phenomenon of genic energy production predicted by subquantum kinetics and proven by numerous a posteriori observations.

These recent findings support the subquantum kinetics cosmology which has long proposed that most of the stars in galaxies are formed by matter expelled outward from a galaxy’s core and that is why dwarf elliptical galaxies eventually adopt a spiral shape and then progressively grow in size. These findings then support the subquantum kinetics view of why there is a close correspondence between the mass of a galaxy’s core (Mother star) and its total mass.


Notes

[1] The precise measure of the stellar mass in Holmberg 15A, reported in the study described below in the article, is (2.5 ± 0.64) × 10¹² solar masses.

[2] Although far away, Holmberg 15A is considered from a cosmological point of view a galaxy of the local Universe, meaning by this expression that region of the observable Universe, which, due to its relative spatial and temporal proximity, contains galaxies in an evolutionary phase comparable to that of the Milky Way. Indeed, the 800 million years or so that light from Holmberg 15A traveled to reach the Earth are only a modest fraction of the age of the Universe, which is 13.8 billion years old. As a result, they are also a small fraction of the evolutionary history of galaxies, which began just a few hundred million years after the Big Bang.

[3] Roughly 10,000−16,000 light-years.

[4] The precise values ​​indicated in the study are (2.75 ± 2.22) × 10¹⁰ solar luminosities and (1.24 ± 1.00) × 10¹¹ solar masses.

[5] (4.0 ± 0.8) × 10¹⁰ solar masses, including the uncertainty margin resulting from the data.

[6] The gravitational sphere of influence is defined in the study as the radius within which a mass exactly equal to that of the SMBH is enclosed. In the case of Holmberg 15A, the radius of the gravitational sphere of influence of its SMBH reported in the study is 3.8 ± 0.37 kiloparsecs.

[7] Outside the event horizon of a black hole, there is a spherical volume, within which the light remains trapped following almost circular orbits until it falls into the black hole or escapes to infinity. It is this light that forms the photonic ring observed by the Event Horizon Telescope in the famous image of the black hole at center of M87, published in April 2019.


The Fate of Planets Near Galactic Center

It was Gregory Benford who used the wonderful phrase ‘the first hard science fiction convention’ to describe what happened at the 100 Year Starship Symposium. It was an apt choice of words. ‘Hard’ science fiction refers to SF that goes out of its way to get the science right, and in which the scientific and technical details play a major role in the development of the plot. Science fiction critic P. Schuyler Miller evidently coined the term in one of his reviews for Astounding Science Fiction back in the 1950s. In many ways, the Symposium operated under a science fictional meme.

Science fiction at its best exists to paint possibilities for us. Some scientific speculations may be remarkable in their own right but only become vivid when portrayed by writers who can make the background science into a scenario that plays out in fictional terms. An obvious case is the classic Isaac Asimov tale “Nightfall,” published in Astounding’s September, 1941 issue. Asimov took us to a place that knew night only once every 2000 years because of the configuration of the six suns in its planetary system. His craft painted a world few would have imagined, and showed us the consequences of its existence upon a civilization there.

All these musings were triggered by the latest news from the University of Leicester, and I’d love to see the science fiction story that might emerge when ‘hard’ SF tackles its findings. Surely someone will tell the story of a civilization too close to galactic center (speaking of places that are well lit!), and the consequences as radiation levels begin to rise to untenable levels on a world too near the central black hole. If interstellar flight is possible, surely it would happen here as a means of species survival.

For black holes seem to be common at galactic center in many galaxies, and in particular the supermassive ones that lurk at the center of galaxies like our Milky Way. Huge cloaks of dust obscure many of these, and a team of scientists led by Sergei Nayakshin at Leicester thinks that collisions between planets and asteroids occurring at speeds up to 1000 kilometers per second could be the cause. Nayakshin’s team argues that the accretion disc around supermassive black holes will eventually form planets, and that planets and asteroids that formed in the outer regions of the disc would be stripped away by the close passage of stars in the disc, given the tight quarters at galactic center.

Released from their host stars, these solids and planets orbit the SMBH independently. Since the velocity kick required to unbind them from the host is in km/s range, whereas the star’s orbital velocity around the SMBH is ∼ 1000 km/s, orbits of the solids are initially only slightly different from that of their hosts. AGN gas discs are expected to be very geometrically thin (e.g., Nayakshin & Cuadra 2005), and if they always lay in the same plane (e.g., the disc galaxy’s mid-plane) then the resulting distribution of solids would be quite thin and planar as well.

So far so good, but planets in this scenario seem bound to come to grief:

However, there is no particularly compelling reason for a single-plane mode of accretion in AGN as the inner parsec is such a tiny region compared with the rest of the bulge (Nayakshin & King 2007), and chaotically-oriented accretion may be much more likely…

Collisions are bad enough, but the planets would have already been sterilized as they orbited the supermassive black holes, says Nayakshin in a related news release:

“Too bad for life on these planets, but on the other hand the dust created in this way blocks much of the harmful radiation from reaching the rest of the host galaxy. This in turn may make it easier for life to prosper elsewhere in the rest of the central region of the galaxy.”

The team takes its lead from the zodiacal dust in our own Solar System, known to be the result of collisions between solid objects like asteroids and comets. And its work may help us understand how black holes grow and affect the galaxies within which they reside. The dust and gas in the inner regions of our own galaxy, much of which might have been expelled or destroyed by this process, would otherwise have contributed to the formation of more stars and planets. The black hole at galactic center would have thus played a significant role in the evolution of the Milky Way.

Image: ‘Light echo’ of dust illuminated by a nearby star V838 Monocerotis as it became 600,000 times more luminous than our Sun in January 2002. The flash is believed to have been caused by a giant collision of some kind, e.g., between two stars or a star and a planet. Collisions of smaller objects, such as asteroids or minor planets near a supermassive black hole could also be dramatic due to the huge collision velocities and would release a lot of dust. Credit: NASA/ESA.

The paper is Nayakshin, et al., “Are SMBHs shrouded by ‘Super-Oort’ clouds of comets and asteroids?” in press at Monthly Notices of the Royal Astronomical Society (preprint). The science fiction story based on it remains to be written.

Comments on this entry are closed.

A civilization to close to the galactic center would probably find themselves in the proverbial frying pan. Planets near the center would experience far more exposure to gamma rays, x-rays, and cosmic rays. My question is, how did complex life and a technological civilization evolve so near the galactic center in the first place? Some scientists theorize there is a “galactic habitable zone” which is friendly to complex life, like us, but anywhere close to the galactic center is well out of this theoretical GHZ!! Any thoughts?

This new research is interesting. Finally, someone is telling us why the galactic center is shrouded in dust- all they told us before is that you can’t see the black hole because visible light cannot penetrate the dust cloud.

Back to the civilization that must escape from the rising radiation levels near the galactic center- wouldn’t high radiation levels make space travel extremely hazardous? If the radiation levels have risen high enough that even a thick atmosphere is not shielding enough, how could a starship survive? If you want to escape dangerous radiation levels, you have to leave your neighborhood altogether.

The distance from Earth to the galactic center is 25000-28000 lys. How far would this civilization need to go to escape the dangerous radiation levels?

Space travel might be easier near the galactic center. There are large clouds of hydrogen near the galactic center, which will make the fusion ramjet a lot more practical. The stars are more densely packed, which will be an incentive for any budding starflight program. If you only have to travel one lightyear instead of four to reach a nearby star, interstellar travel will be easier than it is in our neighborhood.

Once stellar explosions start turning up the heat in their neighborhood, these aliens will turn their ramjets out from the galactic center and head for cooler, safer regions of space. Areas without dangerous gamma rays and x-rays, densely packed stars, nearby novas, and a giant black hole lurking nearby.

However, I think the dangerous radiation and nearby novas would wipe any life before they build interstellar ramjets. I prefer our neighborhood- there might not be any free fuel, but it is a lot safer.

Would a voyage to the galactic center in a starship with a hyperdrive be heroic exploration or insanity?

Speaking of hard sci-fi and galactic centers surely a mention of Greg Egan’s Incandescence is warranted.

(I must mention that if Egan is new to you, then Diaspora is a must read.)

Hi Paul
Stephen Baxter’s “Exultant” in its opening scenes is set amongst the asteroids around the Milky Way’s SMBH. The Core region does get more interesting, the more we study it.

I’ve only just cracked open this paper but something immediately struck me as odd in their reasoning.

First, where did the metals come from that formed these stellar systems near the AGN? Fragmentation beyond a certain threshold distance from the accretion disk. But how did they come to be in the accretion disk to begin with? That must have been from older novae near the AGN, and brought into the accretion disk along with non-metals (hydrogen).

So suggests to me there is a partial recycling of accretion disk material going on, where a portion falls into the SMBH, another portion into the SMBH jets, and the rest into (the paper’s hypothesized) fragments forming these stellar systems. I am having difficulty seeing how this would allow large clouds of metals to exist and have the effects suggested in the paper.

Second, while there are great differences in the opacity of metal (dust) clouds and hydrogen, even if all the material in these putative stellar systems gets pummeled into dust clouds it is still only a small fraction the mass of their stellar parents, and over time I would think that the stellar winds alone would greatly out-mass all the expelled metals.

It just doesn’t feel right. Maybe I’ll have to read further into the paper.

I wrote a long series of novels about these problems (though without this recent research), the Galactic Center Series. I supposed the Center was the best place to live if you were a machine intelligence — plentiful energy resources, indifference to radiation levels, unconcerned with planets as life sites since one could live in raw, radiated space.
It still seems that way to me. I doubt life will evolve nearer than 1000 or more light years from the devouring black hole squatting at the Center.
Yet I supposed humans would go there, seeking the answer to why machine intelligences sought out organic life like us and sought to exterminate it. The astrophysics I did on the magnetic structures around the black hole — which interestingly don’t occur in the Andromeda galaxy — led me to write the rest of the series, after the first two novels.
The Center realm remains the most fascinating region of our galaxy, though not I think a zone for life.

One recent study of the GHZ, Gowanlock, Patton and McConnell (2011) concluded that although the risk from supernovae to the biosphere in the inner galaxy was far greater, the favourable planet-forming conditions made it the most habitable region of the galaxy (i.e. there are sufficient planets there to compensate for the large fraction that experience supernova sterilisation events). From that paper:

From Sections 4.1 and 4.2, we see that SN sterilizations on their own make the inner Galaxy the least hospitable for complex life. However, regarding the planet-metallicity correlation without the effects of SNe makes the inner Galaxy the most hospitable for complex life. When both factors are taken into account, the inner Galaxy is ∼10× more hospitable than the outer Galaxy (Figure 9). This finding indicates that the impact of metallicity on planet formation appears to dominate over the effects of SN sterilizations. Furthermore, the inside-out scenario of Galaxy formation permits the inner region to be more habitable than the outskirts. Neither SN sterilizations nor metal-poor environments are capable of rendering any region inhospitable to complex life at the present day.

Of course this is unlikely to be the final word on the issue…

Andy: What form does this “sterilization” take? I thought a supernova was quite weak even just a few light years away, and a thick atmosphere like the Earth’s does not really let any ionizing radiation through, or does it? If this “sterilization” is just about potential damage to the ozone layer, that would hardly qualify as a life extinguishing event, I think.

Cockroaches, and many bacteria, can tolerate high levels of radiation. I don’t know how they manage it, but life on planets near the galactic center could do the same. Life might take longer to develop, but once it does, *all* life on the planet might be like cockroaches, able to tolerate practically any environment.

Welp.
Larry Niven has us all almost trumped.
Pierson’s Puppeteers are taking their whole kit and caboodle of a Fleet of Worlds out of the galactic center, or where they were near the center.

Say, Greg, I think you said you had some idea to trump Larry?
Didn’t some Russian astronomer have an idea is moving the whole solar system with a big mirror around the sun?

Anybody ever written a story where ‘solid state’ intelligence evolves in a hostile radiation environment , such as near the galactic core.
Then goes on to build ‘wet ware’ things like humans?

The Milky Way and Andromeda galaxy are on a collision course. In about 3 billion years, the two galaxies will collide. That can’t be good for us!
How would one move the Milky Way?
I would say that would take a Kardashev type X!

Eniac: the model for supernova sterilisation used for that analysis is surprisingly enough discussed in the paper. Read section 3.1…

Fred Hoyle’s novel “The Inferno” featured the Milky Way’s centre becoming a full-on quasar. More importantly he used this unlikely scenario to illustrate a factor that I have never seen formally addressed. Unlike supernovas, the power of a galactic core event can be so great as to completely disrupt the galaxy’s magnetic field. In the novel this opened the possibility of every system, even in the galactic disc, being bathed in radiation from the quasar that was so intense that it could completely strip a planet’s atmosphere, but I can’t help but think of milder possibilities such as those highlighted by the cyclical occurrences of mass extinctions on Earth tending to coincide with periods when our system is at locations with the least protection from our galaxy’s field.

My question is how resilient is the bulge of our galaxy to such magnetic field disruptions and how real is the possibility that disruptions thereof by (a series of) core events can play a greater role in the development of higher life than this field does in the disc?

Andy: As I suspected, they appear to assume that a supernova closer than 8 pc will strip aways the ozone layer which will then “sterilize” the planet. I would like to submit these caveats:

1) The ozone layer might be more resilient than we think
2) Something else might replace the ozone layer
3) Life may survive the lack of ozone layer
4) There may be stars with less UV where no ozone layer is needed
5) Bigger planets may have a thicker atmosphere and no need for an ozone layer
6) … etc. etc.

I think there are so many caveats that it is unrealistic to assume that we have any idea about what distance a supernova needs to be to “sterilize” planets. Therefore the inner limit of the GHZ may well be the event horizon of the black hole, or at least not too far from it.

@andy: yes, while most authors, such as Lineweaver, consider the GHZ as an annular ring at about 6-10 kpc from the galactic center, Gowanlock, Patton and McConnell (‘A Model of Habitability Within the Milky Way Galaxy’) model it from 2.5 kpc (or possibly even closer) to at least 12 kpc from the center, with the density of habitable planets in the inner region about 10x as high as in the outer region, also resulting in a rather high estimate of the number of habitable planets in the MW galaxy.

Stephen: scorpions are also known to tolerate very high levels of radiation.

A.A. Jackson: the ‘collision’ of the MW with Andromeda will not be a real collision, but rather a merging of the two galaxies, not uncommon in the history of the universe. Because of the huge distances between the individual stars, there will hardly be any real stellar collisions, in fact very few stars will even be caught in each other’s gravity field (to become secondary binary stars, a very rare event). What may happen is that stars may be disrupted in their galactic orbits and there will probably be a (relatively short duration) outburst of new star formation.

The description of Hoyle’s “Inferno” makes me think of Donald Moffitt’s duology “Second Genesis”/”The Genesis Quest” about an off-shoot of humanity being made by aliens in a distant Galaxy (M101) from radio transmission data. The second book features a very interesting take on the Fermi Paradox based on periodic extinctions, akin to Hoyle’s concept.

The book is now rather out-of-date – eg. M101 is now known to be 21 Mly away, not 37 Mly as was previously thought – but periodic extinctions still drop out of the fossil data. One wonders just what Galaxies do every so often…

One more thought: Isn’t the ozone layer derived from atmospheric oxygen? That would mean that for most of its life Earth did not have one to begin with. Any calculations of GHZ based on supernovas stripping the ozone layer would then be blatantly invalid.

And please all remember that ionizing radiation does not penetrate the atmosphere, so no cockroaches or scorpions required. For UV, there could be a permanent cloud layer, or we could have life that is undersea or underground.

@Eniac: ozone has been detected on both Mars and Venus, there isn’t much of it though…

To me, it would make just as much sense that strong X-rays generate more ozone directly than they destroy indirectly by generating nitrous oxide.

Anyway, after all this and some reading I am now quite convinced that a supernova cannot have a lasting ill effect on life (much less “sterilization”) unless it is close enough to literally fry the place, i.e. provides as much energy as the sun. For the strongest supernovas, this would be less than one light year, which should be an unlikely occurrence even quite close to the galactic center. I would be happy to hear reasons why I am wrong.

Eniac, although I agree with you that supernovas are probably nor such a big risk, your 1 ly ‘safe distance’ may be a bit too optimistic: as I wrote in the previous post (Widening the Red Dwarf Habitable Zone), there are some studies indicating that the most dangerous supernovas, Type Ia, may harm a planet (atmosphere, biosphere) up to about 30 ly.

It shouldn’t be too difficult to make some base caslculations: how much radiation of various types (visible light + IR, UV, X-ray, gamma) reaching our upper atmosphere would be harmful per unit area?
It would be easy to calculate how much that would be at a given distance for a supernova of a particular type.

there are some studies indicating that the most dangerous supernovas, Type Ia, may harm a planet (atmosphere, biosphere) up to about 30 ly.

Well, yes, but what I have come to realize (please tell me if I am wrong) is that those “some studies” are based on the destruction of the ozone layer as the mechanism for sterilization. To me, that is not conclusive (not even close) for all the reasons you will discover if you read my other posts on this matter.

Anyway, after all this and some reading I am now quite convinced that a supernova cannot have a lasting ill effect on life (much less “sterilization”) unless it is close enough to literally fry the place, i.e. provides as much energy as the sun. For the strongest supernovas, this would be less than one light year, which should be an unlikely occurrence even quite close to the galactic center. I would be happy to hear reasons why I am wrong.

What about the expanding shell of high-velocity gas? Sten Odenwald answered the question of what would happen if Betelgeuse went supernova, and the expanding shell of gas would push the suns magnetosphere so far in it would touch the orbit of the Earth.

Apparently, the detonation of Betelgeuse would not be too dangerous for life on Earth, but travelers in interplanetary space would need extra shielding.

Betelgeuse is 160 parsecs (520 light-years) distant. If you were much closer, say within a dozen light years, I’d imagine that the expanding shell of gas might have much worse effects on habitable planets. Do you have any thoughts on this damage mechanism?

Here is what Sten Odenwald hast to say about Betelgeuse going supernova.

Betelgeuse is 160 parsecs (520 light years) distant. If we just consider what could happen as a result of its expanding shell of gas, typical shell velocities are about 10,000 kilometers/sec. The shell would arrive here about 100,000 years after we see the star brightened. The shell would carry perhaps 10 times the mass of the Sun or some 2 x 10^58 protons. The flux of particles in a shell with a radius of 160 parsecs would be about 140,000 protons per second per square centimeter. The solar wind flux, by comparison is about 300 million protons/sec/square centimeter at the Earth’s orbit. So, although detectable, the flux from Betelgeuse probably won’t do much biological damage compared to what the Sun does. However, because the Betelgeuse flux is traveling at 10,000 kilometers/sec compared to the 450 kilometers/sec of the solar wind, the Betelgeuse flux has an effective pressure that is (10,000/450)^2 = 490 times stronger than the solar wind, and spread out over a region much larger than the size of the solar system. This would probably cause the Sun’s magnetopause to collapse from its present radius near 100 AU, to possibly less than the orbit of the Earth. Also, the Earth’s magnetosphere would be compressed, which would cause the energies of the particles in the van Allen belts to be amplified. The environment outside the van allen radiation belts would probably be ‘lethal’ for human exploration of the solar system.

There is also the x-ray flux to contend with. Inside this shell, which would probably take many decades to pass by, there is a bubble of plasma consisting of electrons and magnetic fields which produce copious amounts of X-ray light. We would be subjected to this x-ray flux for 10s of thousands of years until the expanding supernova remnant has aged sufficiently to quench this production mechanism. These X-rays, of the ‘soft’ variety’ would not get down to the Earth’s surface thanks to atmospheric shielding, but travelers in interplanetary space would need some additional shielding from the secondary electrons generated as these x-rays strike the skin of their spacecraft and liberate additional electrons.

I’ve just noticed that you and Ronald were only discussing radiation and the stripping of the ozone layer- but I’d think that the impact of the expanding shell of gas at close range might be bad. Am I wrong? Or is the expanding shell of gas only going to affect the ozone layer, which you don’t seem to think is going to be lethal for life?

Christopher Phoenix, very interesting information from Sten Odenwald, that you passed on.
However, there is one little flaw with the expaning shell/proton flux as described, or maybe not even a flaw, but a detail to bear in mind that makes this proton flux considerably less dangerous:
Quote:
“However, because the Betelgeuse flux is traveling at 10,000 kilometers/sec compared to the 450 kilometers/sec of the solar wind, the Betelgeuse flux has an effective pressure that is (10,000/450)^2 = 490 times stronger than the solar wind”.
This � times srtonger than solar wind’ is *per proton*.
The amount of protons is only 140,000/300 million = about 0.0005

Which means that the total proton energy from Betelgeuse at this distance would only be about 23% of the solar wind.

It’s a pity Odenwald does not elaborate on the amount of X-ray (or did he?).

The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds of thousands of years and over tens of parsecs before its speed falls below the local sound speed.

50 ly, so I am afraid Sten Odenwald is mistaken about the speed with which the Betelgeuse ejecta would arrive here. More likely, they would never arrive at all, having slowed down to a crawl and eventually dissipated before making it 10% of the way. Nevertheless, it seems likely that supernova ejecta could be comparable with the solar wind in density or energy somewhat further away than the 0.5 ly or so that it takes for the electromagnetic radiation energy to be reduced below solar levels. It is not going to kill anything on Earth, but it may cause radiation damage to space craft and unlucky astronauts.


Planets around Supermassive Black Holes are now possible, research reveals

Seen nearly edgewise, the turbulent disk of gas churning around a black hole takes on a crazy double-humped appearance. The black hole’s extreme gravity alters the paths of light coming from different parts of the disk, producing the warped image. The black hole’s extreme gravitational field redirects and distorts light coming from different parts of the disk, but exactly what we see depends on our viewing angle. The greatest distortion occurs when viewing the system nearly edgewise. Above image is a NASA simulation of how a Black Hole might look like.

Credit: NASA’s Goddard Space Flight Center/Jeremy Schnittman

Every galaxy has its heart in the epicenter, and as your human heart, this heart is also vital to the galaxy it exists in. A supermassive black hole is what this organ is in terms of space and science. In the case of our Milky Way, the location of this Black Hole is at the Galactic Core, the rotational center of our galaxy, or the site of the Saggitarius A, a compact astronomical radio source.

Before we jump into knowing more about the planets around a black hole, we need to know what a Black Hole is exactly. It is a region of space-time where the power of gravity is so strong that even light can’t escape from it. After being formed, a black hole absorbs anything that crosses a specific boundary, also known as the event horizon. Each black hole has a doughnut-shaped formation of dust and gases around it, which is called a torus.

The various aspects of the simulation. Image Source: NASA’s Goddard Space Flight Center/Jeremy Schnittman

By absorbing other stars and mixing up with other black holes, we get what is known as a supermassive black hole. A supermassive black hole can have a mass four million times the mass of the sun sitting at the center of our solar system.

But according to the latest research by the National Astronomical Observatory of Japan, it may be possible for planets to orbit them.

Earlier, we had the notion that planets only formed from protoplanetary disks, which were made up of dust and gas found around stars. But this latest research states that planets may also develop from the torus around an SMBH (Supermassive Black Hole).

An artistic rendering of a supermassive black hole. Image: NASA

“The torus of an SMBH has a mass of about 100,000 times the mass of the sun, which is a billion times the mass of the dust in a protoplanetary disk,” says Professor Eiichiro Kokubo and colleagues from the National Astronomical Observatory of Japan in a statement. For the dust in a torus to form a planet, we need different temperatures in the clouds (which is where the black holes play a part). The dust disk around the black holes is so intense that the strong radiation from the central region is stopped and the low-temperature areas are formed.

If the temperature is low enough, the dust can cluster together to form a protoplanet, which is a primary stage in the building of a planet. Small icy particles can be formed from these regions, which can eventually grow into Earth-sized worlds. The distance from the black holes can be as close as just ten light-years away from the black hole with the planet being ten times the mass of our planet Earth.

This can lead to a planetary system around the black holes. This is an astounding find when taken into the fact that the conditions there are very harsh and raspy. The team’s paper is going to be published in the Astrophysics Journal.

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Gravitational Wave Kicks Monster Black Hole Out of Galactic Core

The Hubble Space Telescope captured an image of a quasar named 3C 186 that is offset from the center of its galaxy. Astronomers hypothesize that this supermassive black hole was jettisoned from the center of its galaxy by the recoil from gravitational waves produced by the merging of two supermassive black holes.

This image, taken by NASA's Hubble Space Telescope, reveals an unusual sight: a runaway quasar fleeing from its galaxy's central hub. A quasar is the visible, energetic signature of a black hole. Black holes cannot be observed directly, but they are the energy source at the heart of quasars -- intense, compact gushers of radiation that can outshine an entire galaxy. The green dotted line marks the visible periphery of the galaxy. The quasar, named 3C 186, appears as a bright star just off-center. The quasar and its host galaxy reside 8 billion light-years from Earth. Researchers estimate that it took the equivalent energy of 100 million supernovas exploding simultaneously to jettison the black hole. The most plausible explanation for this propulsive energy is that the monster object was given a kick by gravitational waves unleashed by the merger of two hefty black holes at the center of the host galaxy. The Hubble image combines visible and near-infrared light taken by the Wide Field Camera 3.

This illustration shows how gravitational waves can propel a black hole from the center of a galaxy. The scenario begins in the first panel with the merger of two galaxies, each with a central black hole. In the second panel, the two black holes in the newly merged galaxy settle into the center and begin whirling around each other. This energetic action produces gravitational waves. As the two hefty objects continue to radiate away gravitational energy, they move closer to each other over time, as seen in the third panel. If the black holes do not have the same mass and rotation rate, they emit gravitational waves more strongly in one direction, as shown by the bright area at upper left. The black holes finally merge in the fourth panel, forming one giant black hole. The energy emitted by the merger propels the black hole away from the center in the opposite direction of the strongest gravitational waves.

FOR RELEASE: 1:00 pm (EDT) March 23, 2017

Gravitational Wave Kicks Monster Black Hole Out Of Galactic Core

Newswise — Astronomers have uncovered a supermassive black hole that has been propelled out of the center of a distant galaxy by what could be the awesome power of gravitational waves.

Though there have been several other suspected, similarly booted black holes elsewhere, none has been confirmed so far. Astronomers think this object, detected by NASA's Hubble Space Telescope, is a very strong case. Weighing more than 1 billion suns, the rogue black hole is the most massive black hole ever detected to have been kicked out of its central home.

Researchers estimate that it took the equivalent energy of 100 million supernovas exploding simultaneously to jettison the black hole. The most plausible explanation for this propulsive energy is that the monster object was given a kick by gravitational waves unleashed by the merger of two hefty black holes at the center of the host galaxy.

First predicted by Albert Einstein, gravitational waves are ripples in space that are created when two massive objects collide. The ripples are similar to the concentric circles produced when a hefty rock is thrown into a pond. Last year, the Laser Interferometer Gravitational-Wave Observatory (LIGO) helped astronomers prove that gravitational waves exist by detecting them emanating from the union of two stellar mass black holes, which are several times more massive than the sun.

Hubble's observations of the wayward black hole surprised the research team. "When I first saw this, I thought we were seeing something very peculiar," said team leader Marco Chiaberge of the Space Telescope Science Institute (STScI) and Johns Hopkins University, in Baltimore, Maryland. "When we combined observations from Hubble, the Chandra X-ray Observatory, and the Sloan Digital Sky Survey, it all pointed towards the same scenario. The amount of data we collected, from X-rays to ultraviolet to near-infrared light, is definitely larger than for any of the other candidate rogue black holes."

Chiaberge's paper will appear in the March 30 issue of Astronomy & Astrophysics.

Hubble images taken in visible and near-infrared light provided the first clue that the galaxy was unusual. The images revealed a bright quasar, the energetic signature of a black hole, residing far from the galactic core. Black holes cannot be observed directly, but they are the energy source at the heart of quasars - intense, compact gushers of radiation that can outshine an entire galaxy. The quasar, named 3C 186, and its host galaxy reside 8 billion light-years away in a galaxy cluster. The team discovered the galaxy's peculiar features while conducting a Hubble survey of distant galaxies unleashing powerful blasts of radiation in the throes of galaxy mergers.

"I was anticipating seeing a lot of merging galaxies, and I was expecting to see messy host galaxies around the quasars, but I wasn't really expecting to see a quasar that was clearly offset from the core of a regularly shaped galaxy," Chiaberge recalled. "Black holes reside in the center of galaxies, so it's unusual to see a quasar not in the center."

The team calculated the black hole's distance from the core by comparing the distribution of starlight in the host galaxy with that of a normal elliptical galaxy from a computer model. The black hole had traveled more than 35,000 light-years from the center, which is more than the distance between the sun and the center of the Milky Way.

Based on spectroscopic observations taken by Hubble and the Sloan survey, the researchers estimated the black hole's mass and measured the speed of gas trapped near the behemoth object. Spectroscopy divides light into its component colors, which can be used to measure velocities in space. "To our surprise, we discovered that the gas around the black hole was flying away from the galaxy's center at 4.7 million miles an hour," said team member Justin Ely of STScI. This measurement is also a gauge of the black hole's velocity, because the gas is gravitationally locked to the monster object.

The astronomers calculated that the black hole is moving so fast it would travel from Earth to the moon in three minutes. That's fast enough for the black hole to escape the galaxy in 20 million years and roam through the universe forever.

The Hubble image revealed an interesting clue that helped explain the black hole's wayward location. The host galaxy has faint arc-shaped features called tidal tails, produced by a gravitational tug between two colliding galaxies. This evidence suggests a possible union between the 3C 186 system and another galaxy, each with central, massive black holes that may have eventually merged.

Based on this visible evidence, along with theoretical work, the researchers developed a scenario to describe how the behemoth black hole could be expelled from its central home. According to their theory, two galaxies merge, and their black holes settle into the center of the newly formed elliptical galaxy. As the black holes whirl around each other, gravity waves are flung out like water from a lawn sprinkler. The hefty objects move closer to each other over time as they radiate away gravitational energy. If the two black holes do not have the same mass and rotation rate, they emit gravitational waves more strongly along one direction. When the two black holes collide, they stop producing gravitational waves. The newly merged black hole then recoils in the opposite direction of the strongest gravitational waves and shoots off like a rocket.

The researchers are lucky to have caught this unique event because not every black-hole merger produces imbalanced gravitational waves that propel a black hole in the opposite direction. "This asymmetry depends on properties such as the mass and the relative orientation of the back holes' rotation axes before the merger," said team member Colin Norman of STScI and Johns Hopkins University. "That's why these objects are so rare."

An alternative explanation for the offset quasar, although unlikely, proposes that the bright object does not reside within the galaxy. Instead, the quasar is located behind the galaxy, but the Hubble image gives the illusion that it is at the same distance as the galaxy. If this were the case, the researchers should have detected a galaxy in the background hosting the quasar.

If the researchers' interpretation is correct, the observations may provide strong evidence that supermassive black holes can actually merge. Astronomers have evidence of black-hole collisions for stellar-mass black holes, but the process regulating supermassive black holes is more complex and not completely understood.

The team hopes to use Hubble again, in combination with the Atacama Large Millimeter/submillimeter Array (ALMA) and other facilities, to more accurately measure the speed of the black hole and its gas disk, which may yield more insight into the nature of this bizarre object.

The international team of astronomers in this study consists of M. Chiaberge (STScI and Johns Hopkins University), J. Ely (STScI), E. Meyer (University of Maryland Baltimore County), M. Georganopoulos (University of Maryland Baltimore County and NASA Goddard Space Flight Center), A. Marinucci and S. Bianchi (Università deli Studi Roma Tre, Italy), G. Tremblay (Yale University), B. Hilbert and J. Kotyla (STScI), A. Capetti (INAF - Osservatorio Astrofisico di Torino, Italy), S. Baum (University of Manitoba, Canada), F.D. Macchetto (STScI), G. Miley (University of Leiden, Netherlands), C. O’Dea (University of Manitoba), E. Perlman (Florida Institute of Technology), W. Sparks (STScI) and C. Norman (STScI and Johns Hopkins University).

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

For images and more information about the study and Hubble, visit:

Donna Weaver / Ray VillardSpace Telescope Science Institute, Baltimore, Maryland410-338-4493 / 410-338-4514 [email protected] / [email protected]

Marco ChiabergeSpace Telescope Science Institute andJohns Hopkins University, Baltimore, Maryland 410-338-4980 [email protected]


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