# Could the largest SMBH swallow an entire galaxy?

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It is unlikely that the largest supermassive black hole in the universe has already been discovered, there may be much larger ones.

Are there, or could there be, supermassive black holes large enough to swallow whole galaxies as opposed to the occasional star?

Are there other factors beyond size that would also affect a SMBH's ability to swallow it's own galaxy?

This question might be related to Is there a maximum size for a black hole?

Typical SMBHs do not contribute much to the overall mass of a galaxy, much less than the sun is of the total mass of our solar system. And as we can see, even such mass centered quite nearby does not swallow all objects in the solar system very easily.

While there is no theoretical maximum, in practice - based on simulations - maximum mass for a black hole seems to be around 50 billion solar masses, which will give a radius of 0.01 light years. This is very small compared to the size of the galaxy, so it will not affect the situation much. Thus the main effect of huge black hole vs galaxy would be via plain old gravitation.

The main impediment for a black hole to swallow anything is angular momentum. Any object a black hole is going to consume must shed its angular momentum in order to get closer to event horizon. This is not very easy thing to do, and the main reason black holes are surrounded by discs of extremely hot gas - friction will turn angular momentum into heat, allowing matter to descend towards black hole.

practical maximum of 50 billion suns is due to fact that accretion disc becomes unstable due to new stars forming from it. See for example Andrew King's 2015 paper How Big Can a Black Hole Grow?

Abstract:

I show that there is a physical limit to the mass of a black hole, above which it cannot grow through luminous accretion of gas, and so cannot appear as a quasar or active galactic nucleus. The limit is $$M_{max} ≃ 5 imes 10^{10}$$ M⊙ for typical parameters, but can reach $$M_{max} ≃ 2.7 imes 10^{11}$$ M⊙ in extreme cases (e.g. maximal prograde spin). The largest black hole masses so far found are close to but below the limit. The Eddington luminosity $$≃ 6.5 imes 10^{48} ext{erg s}^{-1}$$ corresponding to $$M_{max}$$ is remarkably close to the largest AGN bolometric luminosity so far observed. The mass and luminosity limits both rely on a reasonable but currently untestable hypothesis about AGN disc formation, so future observations of extreme SMBH masses can therefore probe fundamental disc physics. Black holes can in principle grow their masses above $$M_{max}$$ by non-luminous means such as mergers with other holes, but cannot become luminous accretors again. They might nevertheless be detectable in other ways, for example through gravitational lensing. I show further that black holes with masses ∼ $$M_{max}$$ can probably grow above the values specified by the black-hole - host-galaxy scaling relations, in agreement with observation.

## Ghostly Galaxy –“May Unravel Mystery of Largest Black Holes in the Universe”

.

An enduring mystery is where the largest black holes in the universe come from –massive cosmic paradoxes where creation is destruction that have no memory, yet are said to contain the earliest memories of the universe. An answer may exist about 10 million light-years from Earth, a faint, ghostly galaxy, galaxy NGC 404, named “Mirach’s Ghost” hidden in the line-of-sight glare of a giant red giant star some 200 light years distant.

A research team led by Cardiff University scientists say they are closer to understanding how a supermassive black hole (SMBH) is born thanks to a new technique that has enabled them to zoom in on one of these enigmatic cosmic objects in unprecedented detail. Scientists are unsure as to whether SMBHs were formed in the extreme conditions shortly after the big bang, in a process dubbed a ‘direct collapse’, or were grown much later from ‘seed’ black holes resulting from the death of massive stars.

If the former method were true, SMBHs would be born with extremely large masses – hundreds of thousands to millions of times more massive than our Sun – and would have a fixed minimum size. If the latter were true then SMBHs would start out relatively small, around 100 times the mass of our Sun, and start to grow larger over time by feeding on the stars and gas clouds that live around them.

Astronomers have long been striving to find the lowest mass SMBHs, which are the missing links needed to decipher this problem. The Cardiff-led team has pushed the boundaries, revealing one of the lowest-mass SMBHs, ever observe, at the center of a nearby galaxy, Mirach’s Ghost, weighing less than one million times the mass of our sun.

The findings were made using a new technique with the Atacama Large Millimeter/submillimeter Array (ALMA), a state-of-the-art telescope situated high on the Chajnantor plateau in the Chilean Andes that is used to study light from some of the coldest objects in the Universe.

Seed Theory or Direct Collapse?

“The SMBH in Mirach’s Ghost appears to have a mass within the range predicted by ‘direct collapse’ models,” said Dr Tim Davis from Cardiff University’s School of Physics and Astronomy. “We know it is currently active and swallowing gas, so some of the more extreme ‘direct collapse’ models that only make very massive SMBHs cannot be true.

This on its own is not enough to definitively tell the difference between the ‘seed’ picture and ‘direct collapse’ – we need to understand the statistics for that – but this is a massive step in the right direction.

SMBHs have been found in very distant galaxies as they appeared just a few hundred million years after the big bang, said Dr Marc Sarzi, a member of Davis’ team from the Armagh Observatory & Planetarium. “This suggest that at least some SMBHs could have grown very massive in a very short time, which is hard to explain according to models for the formation and evolution of galaxies.”

“All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others. Looking for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start off,” continued Dr. Sarzi.

The ALMA telescope enabled the team to resolve the gas clouds in the heart of the galaxy, revealing details only 1.5 light years across, making this one of the highest resolution maps of gas ever made of another galaxy. Being able to observe this galaxy with such high resolution enabled the team to overcome a decade’s worth of conflicting results and reveal the true nature of the SMBH at the galaxy’s center.

“Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects,” continued Dr Davis. “If there is a minimum mass for a supermassive black hole, we haven’t found it yet.”

## “Gargantua” –The Black Hole That Could Swallow Our Solar System

This past April 2019, with an event that was as epic as the Apollo 11 landing on the Moon, the world viewed its first image of what had once been purely theoretical, a black hole at the heart of galaxy M87, frozen in time it was 55 million years ago, the size of our solar system, and bigger, with the mass of six and a half billion suns that was captured by a lens the size of planet Earth and 4,000 times more powerful than the Hubble Space Telescope. Over those eons its light took to reach us, said astrophysicist Janna Levin at Columbia University, “we emerged on Earth along with our myths, differentiated cultures, ideologies, languages and varied beliefs,”

(Each day, between Christmas and New Year’s Day, we’ll post one of The Daily Galaxy’s 2019 most viewed posts as ranked by Google Analytics. With our best wishes for The Holidays.)

“The gates of hell, the end of space and time.” That was the black hole was described at the press conference in Brussels where the first ever photograph of one was revealed to an excited audience. And this black hole, a super-massive object at the center of the galaxy Messier 87 (M87 shown above), really is a monster, observed Ellie Mae O’Hagan for The Guardian. “Everything unfortunate enough to get too close to it falls in and never emerges again, including light itself. It’s the point at which every physical law of the known universe collapses. Perhaps it is the closest thing there is to hell: it is an abyss, a moment of oblivion.”

Astronomers have theorized that the galaxy that harbors the black hole grew to its massive size by merging with several other black holes in elliptical galaxy M87, the largest, most massive galaxy in the nearby universe thought to have been formed by the merging of 100 or so smaller galaxies. The M87 black hole’s large size and relative proximity, led astronomers to think that it could be the first black hole that they could actually “see.”

“The Planet Earth Telescope”

The Event Horizon Telescope that imaged the black hole is actually 10 telescopes, linked across four continents in the United States, Mexico, Chile, Spain, and Antarctica, and designed to scan the cosmos in radio waves. For a few days in April 2017, the observatories studied the skies in tandem, creating a gargantuan telescope nearly the size of the planet.

A Galaxy Fell Through It

“A medium-sized galaxy fell through the center of M87, and as a consequence of the enormous gravitational tidal forces, its stars are now scattered over a region that is 100 times larger than the original galaxy!” said Ortwin Gerhard, head of the dynamics group at the Max Planck Institute for Extraterrestrial Physics. Observations July 2018 with ESO’s Very Large Telescope revealed that the giant elliptical galaxy swallowed the entire medium-sized galaxy over the last billion years.

Located about 55 million light-years from Earth, M87 has been a subject of astronomical study for more than 100 years and has been imaged by many NASA observatories, including the Hubble Space Telescope, the Chandra X-ray Observatory and NuSTAR.

In 1918, astronomer Heber Curtis first noticed “a curious straight ray” extending from the galaxy’s center. This bright jet of high-energy material, produced by a disk of material spinning rapidly around the black hole, is visible in multiple wavelengths of light, from radio waves through X-rays. When the particles in the jet impact the interstellar medium (the sparse material filling the space between stars in M87), they create a shockwave that radiates in infrared and radio wavelengths of light but not visible light. In the Spitzer image, the shockwave is more prominent than the jet itself.

Harvard history of science professor Peter L. Galison, a collaborator on Event Horizon Telescope (EHT), said that scientists proposed theoretical arguments for black holes as early as 1916. It was not until the 1970s, however, that researchers substantiated the theory by observing extremely dense areas of matter. Scientists announced in 2016 that, for the first time, they had detected gravitational waves — which many argued were produced by black holes merging, and therefore were evidence that black holes exist.

The image marked the culmination of years of work undertaken by a team of 200 scientists in 59 institutes across 18 countries. The project, to which other scientists at Harvard’s Black Hole Institute also contributed, drew on data collected by eight telescopes whose locations range from Hawaii to the South Pole.

Like Trying to Photograph a Golf Ball on the Moon

In contrast to M87’s monster, 1,500 times more massive than the Milky Way’s central black hole, Sag A* has four million times the mass of our sun, which means that it’s about 44 million kilometers across. That may sound like a big target, but for the telescope array on Earth some 26,000 light-years (or 245 trillion kilometers) away, it’s like trying to photograph a golf ball on the Moon.

“More than 50 years ago, scientists saw that there was something very bright at the center of our galaxy,” Paul McNamara, an astrophysicist at the European Space Agency and an expert on black holes, told AFP’s Marlowe Hood. It has a gravitational pull strong enough to make stars orbit around it very quickly—as fast as 20 years, compared to our Solar System’s journey, which takes about 230 million years to circle the center of the Milky Way.

“We are sitting in the plain of our galaxy—you have to look through all the stars and dust to get to the center,” said McNamara.

## Scientists find monster black holes grow quicker than galaxies and 'could swallow Earth'

Black hole emits accreted matter as energetic radiation without slowing formation in host galaxy

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An international team of astrophysicists has located one of the largest supermassive black holes in the early universe, which is seven BILLION times larger than the Sun and takes up a staggering 10 per cent of its own galaxy.

The researchers, led by Benny Trakhtenbrot from ETH Zurich&rsquos Institute for Astronomy, now fear black holes can continue to expand and eventually outgrow their host galaxy.

Their findings question the current understanding of the rate at which black holes and galaxies grow.

It had previously been understood that black holes at the centre of galaxies grew at the same rate as their host star system.

This meant a black hole would always remain just a fraction - about one per cent - of the size of the growing galaxy.

However, the new research now opens up the possibility the monster supermassive black hole at the centre of our Milky Way galaxy - currently only 4.5million times the size of our Sun - could grow at a faster rate than the rest of the galaxy and swallow our entire solar system, including Earth.

Professor Meg Urry of Yale University, co-author of the study published in the Journal of Science, said: "Black holes are objects that possess such a strong gravitational force that nothing, not even light, can escape.&rdquo

### NASA - Simulations Uncover 'Flashy' Secrets of Merging Black Holes

That means this black hole grew much more efficiently than its galaxy, contradicting the models that predicted a hand-in-hand development

Dr Benny Trakhtenbrot from ETH Zurich&rsquos Institute for Astronomy

Dr Trakhtenbrot's team now want to learn why and how the newly-discovered black hole grew to such a size in the CID-947 galaxy.

He added: "The measurements of CID-947 correspond to the mass of a typical galaxy.

"We therefore have a gigantic black hole within a normal size galaxy.

"The result was so surprising, two of the astronomers had to verify the galaxy mass independently.

"Both came to the same conclusion.&rdquo

In today's local universe, black holes typically reach a mass of 0.2 to 0.5 per cent of their host galaxy&rsquos mass.

Dr Trakhtenbrot added: &ldquoThat means this black hole grew much more efficiently than its galaxy, contradicting the models that predicted a hand-in-hand development.&rdquo

Data collected with Hawaii's Keck Observatory&rsquos newest instrument, called MOSFIRE, discovered the giant black hole in the CID-947 galaxy - 11 billion light years away.

They were able to look at the black hole when the universe was just two billion years old. It is now 14 billion years since the Big Bang.

## Breakthrough in deciphering birth of supermassive black holes

"On the left is shown a colour composite Hubble Space Telescope image of the centre of Mirachs Ghost'. On the right is shown the new ALMA image of this same region, revealing the distribution of the cold, dense gas that swirls around this centre of this object in exquisite detail." Credit: Cardiff University

A research team led by Cardiff University scientists say they are closer to understanding how a supermassive black hole (SMBH) is born thanks to a new technique that has enabled them to zoom in on one of these enigmatic cosmic objects in unprecedented detail.

Scientists are unsure as to whether SMBHs were formed in the extreme conditions shortly after the big bang, in a process dubbed a 'direct collapse', or were grown much later from 'seed' black holes resulting from the death of massive stars.

If the former method were true, SMBHs would be born with extremely large masses—hundreds of thousands to millions of times more massive than our Sun—and would have a fixed minimum size.

If the latter were true then SMBHs would start out relatively small, around 100 times the mass of our Sun, and start to grow larger over time by feeding on the stars and gas clouds that live around them.

Astronomers have long been striving to find the lowest mass SMBHs, which are the missing links needed to decipher this problem.

In a study published today, the Cardiff-led team has pushed the boundaries, revealing one of the lowest-mass SMBHs ever observed at the centre of a nearby galaxy, weighing less than one million times the mass of our sun.

The SMBH lives in a galaxy that is familiarly known as "Mirach's Ghost", due to its close proximity to a very bright star called Mirach, giving it a ghostly shadow.

The findings were made using a new technique with the Atacama Large Millimeter/submillimeter Array (ALMA), a state-of-the-art telescope situated high on the Chajnantor plateau in the Chilean Andes that is used to study light from some of the coldest objects in the Universe.

"The SMBH in Mirach's Ghost appears to have a mass within the range predicted by 'direct collapse' models," said Dr. Tim Davis from Cardiff University's School of Physics and Astronomy.

"We know it is currently active and swallowing gas, so some of the more extreme 'direct collapse' models that only make very massive SMBHs cannot be true.

"This on its own is not enough to definitively tell the difference between the 'seed' picture and 'direct collapse' - we need to understand the statistics for that—but this is a massive step in the right direction."

Black holes are objects that have collapsed under the weight of gravity, leaving behind small but incredibly dense regions of space from which nothing can escape, not even light.

An SMBH is the largest type of black hole that can be hundreds of thousands, if not billions, of times the mass of the Sun.

It is believed that nearly all large galaxies, such as our own Milky Way, contain an SMBH located at its centre.

"SMBHs have also been found in very distant galaxies as they appeared just a few hundred million years after the big bang", said Dr. Marc Sarzi, a member of Dr. Davis' team from the Armagh Observatory & Planetarium.

"This suggest that at least some SMBHs could have grown very massive in a very short time, which is hard to explain according to models for the formation and evolution of galaxies."

"All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others."

"Looking for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start off," continued Dr. Sarzi.

In their study, the international team used brand new techniques to zoom further into the heart of a small nearby galaxy, called NGC404, than ever before, allowing them to observe the swirling gas clouds that surrounded the SMBH at its centre.

The ALMA telescope enabled the team to resolve the gas clouds in the heart of the galaxy, revealing details only 1.5 light years across, making this one of the highest resolution maps of gas ever made of another galaxy.

Being able to observe this galaxy with such high resolution enabled the team to overcome a decade's worth of conflicting results and reveal the true nature of the SMBH at the galaxy's centre.

"Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects," continued Dr. Davis.

"If there is a minimum mass for a supermassive black hole, we haven't found it yet."

The results of the study have been published today in the Monthly Notices of the Royal Astronomical Society.

## Black hole: 'Ghost' galaxy offers major breakthrough in birth of supermassive black holes

### Black holes: Scientists observe galaxies with large telescope

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A team of astronomers at Cardiff University have observed a low-mass supermassive black hole that could be the missing link between two leading theories on how the cosmic monsters are born. Supermassive black holes or SMBHs are the largest known type of black hole, weighing thousands or billions of times more than our Sun. But very little is known about the colossal object and astronomers are still unsure how they are born.

### Trending

According to one theory, supermassive black holes were born shortly after the Big Bang in a process dubbed a "direct collapse".

In this scenario, extremely large supermassive black holes would have been born with a fixed minimum size and weight hundreds of thousands to millions of times than our Sun.

Another theory suggests SMBHs were born much later from "seed" black holes that formed with the dying breath of supermassive stars.

In this case, SMBHs would start out small - about 1,000 times heavier than our Sun - and feed on surrounding stars and gas to gradually grown in mass.

Black holes news: Astronomers still do not know how supermassive black holes are born (Image: GETTY)

Black hole fact sheet: Everything you need to know about black holes (Image: EXPRESS)

In a study published today (July 14) in Monthly Notices of the Royal Astronomical Society, the Cardiff-led team has presented evidence of a supermassive black hole less than one million times the mass of our Sun.

Astronomers have been trying to hunt these low-mass SMBHs for a long time.

The black hole sits at the centre of Mirach's Ghost (NGC 404) - a galaxy about 10 million light-years from us.

Dr Tim Davis from Cardiff University&rsquos School of Physics and Astronomy said: "The SMBH in Mirach's Ghost appears to have a mass within the range predicted by 'direct collapse' models.

"We know it is currently active and swallowing gas, so some of the more extreme 'direct collapse' models that only make very massive SMBHs cannot be true.

### Related articles

We know it is currently active and swallowing gas

Dr Tim Davis, Cardiff University

"This on its own is not enough to definitively tell the difference between the &lsquoseed&rsquo picture and &lsquodirect collapse&rsquo &ndash we need to understand the statistics for that &ndash but this is a massive step in the right direction."

The findings were made using a new technique at the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean Andes, Chile.

The cutting-edge telescope is being used to study some of the coldest objects in the universe.

Astronomers believe nearly all large galaxies, including our own, contain a supermassive black hole in their centre.

In the case of the Milky Way, it is a supermassive black hole about 26,000 light-years away that is known as Sagittarius A* (read: A-star).

Black hole: On the left is a composite Hubble Space Telescope image of the centre of Mirachs Ghost' (Image: NASA/ESA/ALMA)

Black hole news: Black holes can feed on the gas and stars that surround them (Image: GETTY)

Dr Marc Sarzi, a member of Dr Davis&rsquo team from the Armagh Observatory and Planetarium said: "SMBHs have also been found in very distant galaxies as they appeared just a few hundred million years after the Big Bang.

"This suggests that at least some SMBHs could have grown very massive in a very short time, which is hard to explain according to models for the formation and evolution of galaxies.

"All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others.

"Looking for the smallest SMBHs in nearby galaxies could, therefore, help us reveal how SMBHs start off."

The astronomers used a new technique to zoom further into the centre of Mirach's Ghost than ever before.

### Related articles

The technique allowed the astronomers to observe the clouds of gas swirling around the black hole.

The gas clouds were found to only measure about 1.5 light-years across.

Dr Davis said: "Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects.

"If there is a minimum mass for a supermassive black hole, we haven't found it."

## Breakthrough in deciphering birth of supermassive black holes

A research team led by Cardiff University scientists say they are closer to understanding how a supermassive black hole (SMBH) is born thanks to a new technique that has enabled them to zoom in on one of these enigmatic cosmic objects in unprecedented detail.

Scientists are unsure as to whether SMBHs were formed in the extreme conditions shortly after the big bang, in a process dubbed a 'direct collapse', or were grown much later from 'seed' black holes resulting from the death of massive stars.

If the former method were true, SMBHs would be born with extremely large masses - hundreds of thousands to millions of times more massive than our Sun - and would have a fixed minimum size.

If the latter were true then SMBHs would start out relatively small, around 100 times the mass of our Sun, and start to grow larger over time by feeding on the stars and gas clouds that live around them.

Astronomers have long been striving to find the lowest mass SMBHs, which are the missing links needed to decipher this problem.

In a study published today, the Cardiff-led team has pushed the boundaries, revealing one of the lowest-mass SMBHs ever observed at the centre of a nearby galaxy, weighing less than one million times the mass of our sun.

The SMBH lives in a galaxy that is familiarly known as "Mirach's Ghost", due to its close proximity to a very bright star called Mirach, giving it a ghostly shadow.

The findings were made using a new technique with the Atacama Large Millimeter/submillimeter Array (ALMA), a state-of-the-art telescope situated high on the Chajnantor plateau in the Chilean Andes that is used to study light from some of the coldest objects in the Universe.

"The SMBH in Mirach's Ghost appears to have a mass within the range predicted by 'direct collapse' models," said Dr Tim Davis from Cardiff University's School of Physics and Astronomy.

"We know it is currently active and swallowing gas, so some of the more extreme 'direct collapse' models that only make very massive SMBHs cannot be true.

"This on its own is not enough to definitively tell the difference between the 'seed' picture and 'direct collapse' - we need to understand the statistics for that - but this is a massive step in the right direction."

Black holes are objects that have collapsed under the weight of gravity, leaving behind small but incredibly dense regions of space from which nothing can escape, not even light.

An SMBH is the largest type of black hole that can be hundreds of thousands, if not billions, of times the mass of the Sun.

It is believed that nearly all large galaxies, such as our own Milky Way, contain an SMBH located at its centre.

"SMBHs have also been found in very distant galaxies as they appeared just a few hundred million years after the big bang", said Dr Marc Sarzi, a member of Dr. Davis' team from the Armagh Observatory & Planetarium.

"This suggest that at least some SMBHs could have grown very massive in a very short time, which is hard to explain according to models for the formation and evolution of galaxies."

"All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others."

"Looking for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start off," continued Dr. Sarzi.

In their study, the international team used brand new techniques to zoom further into the heart of a small nearby galaxy, called NGC404, than ever before, allowing them to observe the swirling gas clouds that surrounded the SMBH at its centre.

The ALMA telescope enabled the team to resolve the gas clouds in the heart of the galaxy, revealing details only 1.5 light years across, making this one of the highest resolution maps of gas ever made of another galaxy.

Being able to observe this galaxy with such high resolution enabled the team to overcome a decade's worth of conflicting results and reveal the true nature of the SMBH at the galaxy's centre.

"Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects," continued Dr Davis.

"If there is a minimum mass for a supermassive black hole, we haven't found it yet."

The results of the study have been published today in the Monthly Notices of the Royal Astronomical Society.

Michael Bishop
Cardiff University
02920874499/07713325300
[email protected]

2). Cardiff University is recognised in independent government assessments as one of Britain's leading teaching and research universities and is a member of the Russell Group of the UK's most research intensive universities. The 2014 Research Excellence Framework ranked the University 5th in the UK for research excellence. Among its academic staff are two Nobel Laureates, including the winner of the 2007 Nobel Prize for Medicine, Professor Sir Martin Evans. Founded by Royal Charter in 1883, today the University combines impressive modern facilities and a dynamic approach to teaching and research. The University's breadth of expertise encompasses: the College of Arts, Humanities and Social Sciences the College of Biomedical and Life Sciences and the College of Physical Sciences and Engineering, along with a longstanding commitment to lifelong learning.

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.

## Early universe explosion reveals hidden ‘Goldilocks’ black hole that few believed existed

An artist's impression of the discovery | Credit: Carl Knox, OzGrav | Via @ARC_OzGrav/Twitter

Bengaluru: Analysis of light from a gamma-ray burst dating back three billion years ago has revealed the existence of a previously undetected black hole. The black hole is of intermediate mass, an elusive category of black holes that, until a few years ago, many scientists believed didn’t exist.

The gamma-ray burst, known as GRB 950830, was detected in 1995 when the light reached Earth. GRBs are the most energetic form of electromagnetic events in the universe, with short bursts of gamma rays being ejected at the speed of light.

A team of Australian researchers — James Paynter, Rachel Webster and Eric Thrane — from different institutions used the technique of gravitational lensing, where gravity around a massive body bends light coming from a source behind, to identify the intermediate-mass black hole (IMBH) that lensed the gamma-ray burst.

The findings were published in Nature Astronomy journal this week.

### Gravitational lensing

Lensing is thought to occur when light from distant galaxies or events like gamma-ray bursts pass by massive objects in the universe, like stars or black holes.

The gravitational tug of these massive bodies can bend the light, causing the source to look distorted or appear in a different position.

When gravitational lensing is weak, it can distort the distant object or galaxy, making it appear magnified or stretched out. But when it is strong, it can bend light to such an extent that multiple images of the same galaxy are visible to us simultaneously.

Gravitational lensing is difficult to measure for individual galaxies, but clusters of galaxies tend to exhibit similar lensing patterns, enabling mathematical deduction.

Paynter, Webster (both from University of Melbourne) and Thrane (Monash University and OzGrav, the Australian Research Council Centre of Excellence for Gravitational Wave Discovery) combed through thousands of gamma-ray bursts looking for data that could point to gravitational lensing by objects that appear invisible.

​ Gamma-ray bursts are created when a high-mass star collapses and forms a neutron star or black hole. ​

Through extensive calculations, the authors concluded that this IMBH candidate likely carries a mass of tens of thousands solar masses.

### Intermediate-mass black holes

IMBHs are a class of a black hole with a mass 100 to 100,000 times that of the Sun. There are two other types of black holes: the ones with a mass of less than 100 times that of the Sun are called stellar-mass black holes, while the ones with a mass greater than 100,000 times that — sometimes even billions of solar masses — are called supermassive black holes (SMBH).

Both stellar black holes and SMBHs are common. The closest black hole to Earth, a part of the system HR 6819, is active just 1,000 light years from us. The smallest known black hole is GRO J0422+32, discovered in 1992 at around 7,800 light years from Earth, which measures 2.1 times the solar mass.

Meanwhile, the centre of the Milky Way galaxy hosts a supermassive black hole called Sgr A* (pronounced “Sagittarius A star”) that is 26,000 light years from Earth and holds a mass of at least 40 lakh times the Sun’s. Every galaxy is theorised to have an SMBH at its centre, around which the entire galaxy revolves.

The first ever black hole detected, Cygnus X-1 in 1964, has 21 solar masses . Since then, researchers have discovered numerous black holes of the two extreme categories. But IMBHs — which have come to court the moniker “Goldilocks” in a reference drawn from the popular 19th-century fairytale — have been mysteriously difficult to detect.

Since 2004, new research has been published regularly with a handful of candidates, most claiming to be the “first evidence” of an IMBH. However, no findings have confirmed the existence of one directly yet.

In 2020, the Hubble Space Telescope provided the “best evidence” for an IMBH. This was followed by the detection of a gravitational wave from the merger of two IMBHs weighing 85 times and 66 times the solar mass.

The first direct picture of a black hole was obtained in 2019. It is the only black hole imaged directly , and the image has since been improved by mapping the magnetic fields around the SMBH.

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## “Ghost” Galaxy Offers Breakthrough in Deciphering Birth of Supermassive Black Holes

“On the left is shown a color composite Hubble Space Telescope image of the center of `Mirachs Ghost’. On the right is shown the new ALMA image of this same region, revealing the distribution of the cold, dense gas that swirls around this center of this object in exquisite detail.” Credit: Cardiff University

Astronomers zoom in on black hole with one of the lowest masses ever observed in nearby “ghost” galaxy.

A research team led by Cardiff University scientists say they are closer to understanding how a supermassive black hole (SMBH) is born thanks to a new technique that has enabled them to zoom in on one of these enigmatic cosmic objects in unprecedented detail.

Scientists are unsure as to whether SMBHs were formed in the extreme conditions shortly after the big bang, in a process dubbed a ‘direct collapse’, or were grown much later from ‘seed’ black holes resulting from the death of massive stars.

If the former method were true, SMBHs would be born with extremely large masses — hundreds of thousands to millions of times more massive than our Sun — and would have a fixed minimum size.

If the latter were true then SMBHs would start out relatively small, around 100 times the mass of our Sun, and start to grow larger over time by feeding on the stars and gas clouds that live around them.

Astronomers have long been striving to find the lowest mass SMBHs, which are the missing links needed to decipher this problem.

In a study published today, the Cardiff-led team has pushed the boundaries, revealing one of the lowest-mass SMBHs ever observed at the center of a nearby galaxy, weighing less than one million times the mass of our sun.

The SMBH lives in a galaxy that is familiarly known as “Mirach’s Ghost,” due to its close proximity to a very bright star called Mirach, giving it a ghostly shadow.

The findings were made using a new technique with the Atacama Large Millimeter/submillimeter Array (ALMA), a state-of-the-art telescope situated high on the Chajnantor plateau in the Chilean Andes that is used to study light from some of the coldest objects in the Universe.

“The SMBH in Mirach’s Ghost appears to have a mass within the range predicted by ‘direct collapse’ models,” said Dr. Tim Davis from Cardiff University’s School of Physics and Astronomy.

“We know it is currently active and swallowing gas, so some of the more extreme ‘direct collapse’ models that only make very massive SMBHs cannot be true.

“This on its own is not enough to definitively tell the difference between the ‘seed’ picture and ‘direct collapse’ — we need to understand the statistics for that — but this is a massive step in the right direction.”

Black holes are objects that have collapsed under the weight of gravity, leaving behind small but incredibly dense regions of space from which nothing can escape, not even light.

An SMBH is the largest type of black hole that can be hundreds of thousands, if not billions, of times the mass of the Sun.

It is believed that nearly all large galaxies, such as our own Milky Way, contain an SMBH located at its center.

“SMBHs have also been found in very distant galaxies as they appeared just a few hundred million years after the big bang,” said Dr. Marc Sarzi, a member of Dr. Davis’ team from the Armagh Observatory & Planetarium.

“This suggest that at least some SMBHs could have grown very massive in a very short time, which is hard to explain according to models for the formation and evolution of galaxies.”

“All black holes grow as they swallow gas clouds and disrupt stars that venture too close to them, but some have more active lives than others.”

“Looking for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start off,” continued Dr. Sarzi.

In their study, the international team used brand new techniques to zoom further into the heart of a small nearby galaxy, called NGC404, than ever before, allowing them to observe the swirling gas clouds that surrounded the SMBH at its center.

The ALMA telescope enabled the team to resolve the gas clouds in the heart of the galaxy, revealing details only 1.5 light-years across, making this one of the highest resolution maps of gas ever made of another galaxy.

Being able to observe this galaxy with such high resolution enabled the team to overcome a decade’s worth of conflicting results and reveal the true nature of the SMBH at the galaxy’s center.

“Our study demonstrates that with this new technique we can really begin to explore both the properties and origins of these mysterious objects,” continued Dr. Davis.

“If there is a minimum mass for a supermassive black hole, we haven’t found it yet.”

Reference: “Revealing the intermediate-mass black hole at the heart of the dwarf galaxy NGC 404 with sub-parsec resolution ALMA observations” by Timothy A Davis, Dieu D Nguyen, Anil C Seth, Jenny E Greene, Kristina Nyland, Aaron J Barth, Martin Bureau, Michele Cappellari, Mark den Brok, Satoru Iguchi, Federico Lelli, Lijie Liu, Nadine Neumayer, Eve V North, Kyoko Onishi, Marc Sarzi, Mark D Smith and Thomas G Williams, 14 July 2020, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/staa1567

## Wandering Supermassive Black Holes May Hide Alien Civilizations

Which concept is more believable (or unbelievable) … that the Milky Way galaxy has wandering supermassive black holes or that supermassive black holes (wandering or otherwise) could be hiding advanced alien civilizations? Both concepts have been seen in models and both could someday have an impact on Earth. Is it too soon to either run or put out a welcome mat … or both?

Supermassive black holes are the largest type of black hole and as such usually occupy the premier location in a galaxy – namely, smack dab in the middle. That’s the case with the Milky Way galaxy, whose supermassive black hole is at its center at Sagittarius A* (A-star), which is near the border of the constellations Sagittarius and Scorpius. While not yet proven, astronomers assume that every galaxy has a supermassive black hole at its center. It’s also likely that some may have two in that same center location. Now, a new study published in the Astrophysical Journal Letters proposes that some galaxies, including the Milky Way, have wandering supermassive black holes whose cause and possible effects are a concern for other stars.

Study lead author Michael Tremmel (who summarizes it in this video) reports that researchers from Yale, the University of Washington, Institut d’Astrophysique de Paris, and University College London used a new simulation model appropriately named Romulus (one of the twin founders of Rome) to predict the existence of these wandering supermassive black holes – appropriate because the secondary wandering holes are likely the result of the incomplete merging of two galaxies where the bigger SMBH didn’t assimilate the smaller one. The smaller SMBHs, being too far out to absorb gas and generate radiation, are invisible, but could still be deadly to a nearby star and its planets. Like us?

“It is extremely unlikely that any wandering supermassive black hole will come close enough to our Sun to have any impact on our solar system. We estimate that a close approach of one of these wanderers that is able to affect our solar system should occur every 100 billion years or so, or nearly 10 times the age of the universe.”

The amount of money wagered on lotteries shows how little humans respect long odds, but something far different that annihilation might also occur if our solar system is approached by a SMBH … alien contact. With the news of the wandering SMBHs, it’s worth revisiting an older report where Russian cosmologist Vyacheslav Vyacheslav Dokuchaev at Moscow’s Institute for Nuclear Research and the Russian Academy of Sciences proposed that supermassive black holes are so large, their centers may have enough space that their gravitational pull is less, allowing for planets to potentially exist. And not just planets, but also …

“We hypothesize that the advanced civilizations may live safely inside the supermassive black holes in the galactic nuclei being invisible from the outside.”

Really? Dokuchaev says supermassive black holes have two ‘point of no return’ event horizons with a space between them.

“The naked central singularity illuminates the orbiting internal planets and provides the energy supply for life supporting. This internal black hole domain, hidden by the two horizons from the whole external universe, is indeed a suitable place for safe inhabitation.”

REALLY? Dokuchaev admits that this advanced civilization would have to be advanced enough to deal with “huge tidal forces and massive energy densities … [and] causality violations, where the rules of space-time don’t apply.” If they’re so advanced, why don’t they move to a better galactic neighborhood?

So, a simulator shows that supermassive black holes are wandering the Milky Way, a Russian cosmologist says they may contain advanced life forms, and the odds of either getting close to us are worse than the lottery … but not impossible.

What do we know for sure? Supermassive Black Hole is already a great song and the Naked Singularities would be a great name for a band.