Primordial Black Holes Might be Cosmic Gold Diggers

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Neutron stars might have black hole parasites in their cores (NASA’s Goddard Space Flight Center)

When the universe’s first black holes appeared is one of the biggest mysteries in astrophysics. Were they born immediately after the Big Bang 13.8 billion years ago? Or did they pop into existence after the first population of massive stars exploded as supernovas millions of years later?

The origin of primordial black holes isn’t a trivial matter. In our modern universe, the majority of galaxies have supermassive black holes in their cores and we’re having a hard time explaining how they came to be the monsters they are today. For them to grow so big, there must have been a lot of primordial black holes formed early in the universe’s history clumping together to form progressively more massive black holes.

Now, in a new study published in Physical Review Letters, Alexander Kusenko and Eric Cotner, who both work at the University of California, Los Angeles (UCLA), have arrived at an elegant theory as to how the early universe birthed black holes.

Primordial beginnings

Immediately after the Big Bang, the researchers suggest that a uniform energy field pervaded our baby universe. In all the superheated chaos, long before stars started to form, this energy field condensed as “Q balls” and clumped together. These clumps of quasi-matter collapsed under gravity and the first black holes came to be.

These primordial black holes have been singled out as possible dark matter candidates (classed as massive astrophysical compact halo objects, or “MACHOs”) and they may have coalesced to quickly seed the supermassive black holes. In short: if these things exist, they could explain a few universal mysteries.

But in a second Physical Review Letters study, Kusenko teamed up with Volodymyr Takhistov (also from UCLA) and George Fuller, at UC San Diego, to investigate how these primordial black holes may have triggered the formation of heavy elements such as gold, platinum and uranium — through a process known as r-process (a.k.a. rapid neutron capture process) nucleosynthesis.

It is thought that energetic events in the universe are responsible for the creation for approximately half of elements heavier than iron. Elements lighter than iron (except for hydrogen, helium and lithium) were formed by nuclear fusion inside the cores of stars. But the heavier elements formed via r-process nucleosynthesis are thought to have been sourced via supernova explosions and neutron star collisions. Basically, the neutron-rich debris left behind by these energetic events seeded regions where neutrons could readily fuse, creating heavy elements.

These mechanisms for heavy element production are far from being proven, however.

“Scientists know that these heavy elements exist, but they’re not sure where these elements are being formed,” Kusenko said in a statement. “This has been really embarrassing.”

A cosmic goldmine

So what have primordial black holes got to do with nucleosynthesis?

If we assume the universe is still populated with these ancient black holes, they may collide with spinning neutron stars. When this happens, the researchers suggest that the black holes will drop into the cores of the neutron stars.

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Alexander Kusenko/UCLA

Like a parasite eating its host from the inside, material from the neutron star will be consumed by the black hole in its core, causing the neutron star to shrink. As it loses mass, the neutron star will spin faster, causing neutron-rich debris to fling off into space, facilitating (you guessed it) r-process nucleosynthesis, creating the heavy elements we know and love — like gold. The whole process is expected to take about 10,000 years before the neutron star is no more.

So, where are they?

There’s little evidence that primordial black holes exist, so the researchers suggest further astronomical work to study the light of distant stars that may flicker by the passage of invisible foreground black holes. The black holes’ gravitational fields will warp spacetime, causing the starlight to dim and brighten.

It’s certainly a neat theory to think that ancient black holes are diving inside neutron stars to spin them up and create gold in the process, but now astronomers need to prove that primordial black holes are out there, possibly contributing to the dark matter budget of our universe.

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Repeating “Fast Radio Bursts” Detected in Another Galaxy — Probably Not Aliens, Interesting Anyway

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The Green Bank Radio Telescope (NRAO)

A radio astronomy project intended to find signals from intelligent aliens has announced the intriguing detections of “repeating” fast radio bursts (FRBs) from a single source in a galaxy three billion light-years distant. This is definitely an exciting development, but probably not for the reasons you think.

The ambitious $100 million Breakthrough Listen project aims to scan a million stars in our galaxy and dozens of nearby galaxies across radio frequencies and visible light in hopes of discovering a bona fide artificial signal that could be attributed to an advanced alien civilization. But in its quest, Breakthrough Listen has studied the signals emanating from FRB 121102 — and recorded 15 bursts — to better understand what might be causing it.

FRBs remain a mystery. First detected by the Parkes Radio Telescope in Australia, these very brief bursts of radio emissions seemed to erupt from random locations in the sky. But the same location never produced another FRB, making these bizarre events very difficult to understand and impossible to track.

Hypotheses ranged from powerful bursts of energy from supernovae to active galactic nuclei to (you guessed it) aliens, but until FRB 121102 repeated itself in 2015, several of these hypotheses could be ruled out. Supernovae, after all, only have to happen once — this FRB source is repeating, possibly hinting at a periodic energetic phenomenon we don’t yet understand. Also, because FRB 121102 is a repeater, in 2016 astronomers could trace back the location of its source to a dwarf galaxy 3 billion light-years from Earth.

Now we ponder the question: What in the universe generates powerful short bursts of radio emissions from inside a dwarf galaxy, repeatedly?

Using the Green Bank Telescope in the West Virginia, scientists of Breakthrough Listen recorded 400 TB of data over a five hour period on Aug. 26. In these data, 15 FRBs were recorded across the 4 to 8 GHz radio frequency band. The researchers noted the characteristic frequency dispersion of these FRBs, caused by the signal traveling through gas between us and the source.

Now that we have dedicated and extremely detailed measurements of this set of FRBs, astrophysicists can get to work trying to understand what natural phenomenon is generating these bursts. This is the story so far, but as we’re talking radio emissions, mysteries and a SETI project, aliens are never far away…

Probably Not Aliens

It may be exciting to talk about the possibility of aliens generating this signal — as a means of communication or, possibly, transportation via beamed energy — but that avenue of speculation is just that: speculation. But to speculate is understandable. FRBs are very mysterious and, so far, astrophysicists don’t have a solid answer.

But this mystery isn’t without precedent.

In 1967, astronomers Jocelyn Bell Burnell and Antony Hewish detected strange radio pulses emanating from a point in the sky during a quasar survey to study interplanetary scintillation (IPS). The mysterious pulses had an unnaturally precise period of 1.33 seconds. At the time, nothing like it had been recorded and the researchers were having a hard time explaining the observations. But in the back of their minds, they speculated that, however unlikely, the signal might be produced by an alien intelligence.

During a dinner speech in 1977, Bell Burnell recalled the conundrum they faced:

“We did not really believe that we had picked up signals from another civilization, but obviously the idea had crossed our minds and we had no proof that it was an entirely natural radio emission. It is an interesting problem – if one thinks one may have detected life elsewhere in the universe how does one announce the results responsibly? Who does one tell first? We did not solve the problem that afternoon, and I went home that evening very cross here was I trying to get a Ph.D. out of a new technique, and some silly lot of little green men had to choose my aerial and my frequency to communicate with us.”

This first source was nicknamed “LGM-1” (as in “Little Green Men-1”), but far from being an artificial source, the duo had actually identified the first pulsar — a rapidly-spinning, highly magnetized neutron star that generates powerful emissions from its precessing magnetic poles as it rotates.

This is how science works: An interesting signal is detected and theories are formulated as to how that signal could have been generated.

In the case of LGM-1, it was caused by an as-yet-to-be understood phenomenon involving a rapidly-spinning stellar corpse. In the case of FRB 121102, it is most likely an equally as compelling phenomenon, only vastly more powerful.

The least likely explanation of FRB 121102 makes a LOT of assumptions, namely: aliens that have become so incredibly technologically advanced (think type II or even type III on the Kardashev Scale) that they can fire a (presumably) narrow beam directly at us through intergalactic space over and over again (to explain the repeated FRB detections) — the odds of which would be vanishingly low — unless the signal is omnidirectional, so they’d need to access way more energy to make this happen. Another assumption could be that intelligent, technologically advanced civilizations are common, so it was only a matter of time before we saw a signal like FRB 121102.

Or it could be a supermassive black hole (say) doing something very energetic that science can’t yet explain.

Occam’s razor suggests the latter might be more reasonable.

This isn’t to say aliens don’t exist or that intelligent aliens aren’t transmitting radio signals, it just means the real cause of this particular FRB repeater is being generated by a known phenomenon doing something unexpected, or a new (and potentially more exciting) phenomenon that’s doing something exotic and new. It doesn’t always have to be aliens.

h/t:

We’re Really Confused Why Supermassive Black Holes Exist at the Dawn of the Cosmos

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ESO

Supermassive black holes can be millions to billions of times the mass of our sun. To grow this big, you’d think these gravitational behemoths would need a lot of time to grow. But you’d be wrong.

When looking back into the dawn of our universe, astronomers can see these monsters pumping out huge quantities of radiation as they consume stellar material. Known as quasars, these objects are the centers of primordial galaxies with supermassive black holes at their hearts.

Now, using the twin W. M. Keck Observatory telescopes on Hawaii, researchers have found three quasars all with billion solar mass supermassive black holes in their cores. This is a puzzle; all three quasars have apparently been active for short periods and exist in an epoch when the universe was less than a billion years old.

Currently, astrophysical models of black hole accretion (basically models of how fast black holes consume matter — likes gas, dust, stars and anything else that might stray too close) woefully overestimate how long it takes for black holes to grow to supermassive proportions. What’s more, by studying the region surrounding these quasars, researchers at the Max Planck Institute for Astronomy (MPIA) in Germany have found that these quasars have been active for less than 100,000 years.

To put it mildly, this makes no sense.

“We don’t understand how these young quasars could have grown the supermassive black holes that power them in such a short time,” said lead author Christina Eilers, a post-doctorate student at MPIA.

Using Keck, the team could take some surprisingly precise measurements of the quasar light, thereby revealing the conditions of the environment surrounding these bright baby galaxies.

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MPIA

Models predict that after forming, quasars began funneling huge quantities of matter into the central black holes. In the early universe, there was a lot of matter in these baby galaxies, so the matter was rapidly consumed. This created superheated accretion disks that throbbed with powerful radiation. The radiation blew away a comparatively empty region surrounding the quasar called a “proximity zone.” The larger the proximity zone, the longer the quasar had been active and therefore the size of this zone can be used to gauge the age (and therefore mass) of the black hole.

But the proximity zones measured around these quasars revealed activity spanning less than 100,000 years. This is a heartbeat in cosmic time and nowhere near enough time for a black hole pack on the supermassive pounds.

“No current theoretical models can explain the existence of these objects,” said Joseph Hennawi, who led the MPIA team. “The discovery of these young objects challenges the existing theories of black hole formation and will require new models to better understand how black holes and galaxies formed.”

The researchers now hope to track down more of these ancient quasars and measure their proximity zones in case these three objects are a fluke. But this latest twist in the nature of supermassive black holes has only added to the mystery of how they grow to be so big and how they relate to their host galaxies.

Supermassive black hole with torn-apart star (artist’s impress
A supermassive black hole consumes a star in this artist’s impression (ESO)

These questions will undoubtedly reach fever-pitch later this year when the Event Horizon Telescope (EHT) releases the first radio images of the 4 million solar mass black hole lurking at the center of our galaxy. Although it’s a relative light-weight among supermassives, direct observations of Sagittarius A* may uncover some surprises as well as confirm astrophysical models.

But as for how supermassive black holes can possibly exist at the dawn of our universe, we’re obviously missing something — a fact that is as exciting as it is confounding.

A Powerful Galactic Explosion Has Been Detected — and Astronomers Aren’t Sure What Caused It

NASA/CXC/Pontifical Catholic Univ./F.Bauer et al.

A long time ago in a galaxy far, far away…

NASA’s Chandra X-ray Observatory has detected a mysterious explosion in deep space and, although astronomers have some suspected causes for the incredibly powerful event, there’s a possibility that it could be something we’ve never witnessed before.

The signal is the deepest X-ray source ever recorded and it appears to be related to a galaxy located approximately 10.7 billion light-years away (it therefore happened 10.7 billion years ago, when the universe was only three billion years old). Over the course of only a few minutes in October 2014, this event produced a thousand times more energy than all the stars in its galaxy. Before that time, there were no X-rays originating from this location and there’s been nothing since.

The explosion occurred in a region of sky called the Chandra Deep Field-South (CDF-S) — the event was therefore designated “CDF-S XT1” — and archived observations of that part of the sky by the NASA/ESA Hubble Space Telescope and NASA’s Spitzer space telescope revealed that it originated from within a faint, small galaxy.

“Ever since discovering this source, we’ve been struggling to understand its origin,” said Franz Bauer of the Pontifical Catholic University of Chile in Santiago, Chile, in a statement. “It’s like we have a jigsaw puzzle but we don’t have all of the pieces.”

One possibility is that we could be looking at the effects of a huge stellar explosion, known as a gamma-ray burst (GRB). GRBs are caused when a massive star implodes and blasts powerful gamma-rays as intense beams from its poles — think super-sized supernova on acid. They can also be caused by cataclysmic collisions between two neutron stars or a neutron star and black holes. Should one of those beams be directed at Earth, over 10.7 billion light-years of travel, the gamma-ray radiation would have dispersed and arrived here at a lower, X-ray energy, possibly explaining CDF-S XT1.

Alternatively, the signal may have been caused by the rapid destruction of a white dwarf star falling into a black hole. Alas, none of these explanations fully fit the observation and it could, actually, be a new phenomenon.

“We may have observed a completely new type of cataclysmic event,” said Kevin Schawinski, of ETH Zurich in Switzerland. “Whatever it is, a lot more observations are needed to work out what we’re seeing.”

So, in short, watch this space.

The research will be published in the June edition of the journal Monthly Notices of the Royal Astronomical Society and is available online.

Plasma ‘Soup’ May Have Allowed Ancient Black Holes to Beef up to Supermassive Proportions

How ancient supermassive black holes grew so big so quickly is one of the biggest mysteries hanging over astronomy — but now researchers think they know how these behemoths packed on the pounds.

John Wise, Georgia Tech

Supermassive black holes are the most extreme objects in the universe. They can grow to billions of solar masses and live in the centers of the majority of galaxies. Their extreme gravities are legendary and have the overwhelming power to switch galactic star formation on and off.

But as our techniques have become more advanced, allowing us to look farther back in time and deeper into the distant universe, astronomers have found these black hole behemoths lurking, some of which are hundreds of millions to billions of solar masses. This doesn’t make much sense; if these objects slowly grow by swallowing cosmic dust, gas, stars and planets, how did they have time only a few hundred million years after the Big Bang to pack on all those pounds?

Well, when the universe was young, it was a very different place. Closely-packed baby galaxies generated huge quantities of radiation and this radiation had a powerful influence over star formation processes in neighboring galaxies. It is thought that massive starburst galaxies (i.e. a galaxy that is dominated by stellar birth) could produce so much radiation that they would, literally, snuff-out star formation in neighboring galaxies.

Stars form in vast clouds of cooling molecular hydrogen and, when star birth reigns supreme in a galaxy, black holes have a hard time accreting matter to bulk up — these newly-formed stars are able to escape the black hole’s gravitational grasp. But in the ancient universe, should a galaxy that is filled with molecular hydrogen be situated too close to a massive, highly radiating galaxy, these clouds of molecular hydrogen could be broken down, creating clouds of ionized hydrogen plasma — stuff that isn’t so great for star formation. And this material can be rapidly consumed by a black hole.

According to computer simulations of these primordial galaxies of hydrogen plasma, if any black hole is present in the center of that galaxy, it will feed off this plasma “soup” at an astonishingly fast rate. These simulations are described in a study published in the journal Nature Astronomy.

“The collapse of the galaxy and the formation of a million-solar-mass black hole takes 100,000 years — a blip in cosmic time,” said astronomer Zoltan Haiman, of Columbia University, New York. “A few hundred-million years later, it has grown into a billion-solar-mass supermassive black hole. This is much faster than we expected.”

But for these molecular hydrogen clouds to be broken down, the neighboring galaxy needs to be at just the right distance to “cook” its galactic neighbor, according to simulations that were run for several days on a supercomputer.

“The nearby galaxy can’t be too close, or too far away, and like the Goldilocks principle, too hot or too cold,” said astrophysicist John Wise, of the Georgia Institute of Technology.

The researchers now hope to use NASA’s James Webb Space Telescope, which is scheduled for launch next year, to look back to this era of rapid black hole formation, with hopes of actually seeing these black hole feeding processes in action. Should observations agree with these simulations, we may finally have some understanding of how these black hole behemoths grew so big so quickly.

“Understanding how supermassive black holes form tells us how galaxies, including our own, form and evolve, and ultimately, tells us more about the universe in which we live,” added postdoctoral researcher John Regan, of Dublin City University, Ireland.

Some Galaxies Die Young… Others Recycle

Some galaxies undergo a rapid star formation phase, losing stellar gases to intergalactic space, others choose to recycle, thereby extending their star forming lifespans.
Some galaxies undergo a rapid star formation phase, losing stellar gases to intergalactic space, others choose to recycle, thereby extending their star forming lifespans (NASA, ESA, and A. Feild (STScI))

It sounds like an over-hyped public service announcement: If you don’t recycle, you’ll die a premature death.

But in the case of galaxies, according to three new Science papers based on Hubble Space Telescope data, this is a reality. Should a galaxy “go green,” reusing waste stellar gas contained within huge halos situated outside their visible disks, they will fuel future star-birth cycles, prolonging their lifespans.

Sadly for “starburst” galaxies — galaxies that undergo rapid star generation over very short time periods — they care little for recycling, resulting in an untimely death.

Using data from Hubble’s Cosmic Origins Spectrograph (COS), three teams studied 40 galaxies (including the Milky Way) and discovered vast halos of waste stellar gases. Contained within these spherical reservoirs — extending up to 450,000 light-years from their bright disks of stars — light elements such as hydrogen and helium were found to be laced with heavier elements like carbon, oxygen, nitrogen and neon. There’s only one place these heavy elements could have come from: fusion processes in the cores of stars and supernovae.

Interestingly, the quantity of heavy elements contained within the newly-discovered halos is similar to what is contained in the interstellar gases within the galaxies themselves.

“There’s as much heavy elements out in the halos of the galaxies as there is in their interstellar medium, that is what shocked us.” said Jason Tumlinson, an astronomer for the Space Telescope Science Institute in Baltimore, Md., in an interview for my Discovery News article “Galaxies That Don’t Recycle Live Hard, Die Young.”

But these heavy elements are stored in halos outside the galaxies; how the heck did it get there?

According to the researchers, powerful stellar winds jetting into intergalactic space have been observed, transporting the heavy elements with them. But there’s a catch. If the outflow is too strong, waste stellar gases are ejected from the galaxies completely. Unfortunately for one sub-set of galaxies, powerful stellar outflows come naturally.

Starburst galaxies rapidly generate stars, ejecting speedy streams of stellar waste gas. Some of these streams have been clocked traveling at 2 million miles per hour, escaping from the galaxy forever. In the case of a starbust galaxy, a “recycling halo” cannot be re-supplied — future star birth is therefore killed off.

“We found the James Dean or Amy Winehouse of that population, you know, the galaxies that lived fast and died young,” Tumlinson pointed out. “(Todd) Tripp’s team studied that in their paper.”

“That paper used a galaxy that is known as a ‘post-star burst galaxy’ and its spectrum showed that it had a very robust star burst (phase),” he continued. “It was one of those live fast, die young galaxies.”

Although fascinating, one idea struck me the hardest. On asking Tumlinson to speculate on how galactic recycling of stellar material may impact us, he said:

“Your body is 70 percent water and every water molecule has an oxygen atom in it. The theorists say the recycling time (in the Milky Way’s halo) is approximately a billion years, so that means — potentially — that some of the material (oxygen) inside your body has cycled in and out of the galaxy ten times in the history of the galaxy. At least once, maybe up to ten times.”

As Carl Sagan famously said: “We’re made of star stuff;” perhaps this should be rephrased to: “We’re made of recycled star stuff.”

Publications:

M87’s Obese Black Hole: A Step Closer to the Event Horizon Telescope

The black hole lurking inside galaxy M87 has a mass of 6.6 billion suns, according to today's announcement (NASA)

Fresh from the Department Of I Really Shouldn’t Have Eaten That Last Binary, astronomers attending the American Astronomical Society meeting in Seattle, Wash., have announced a supermassive black hole residing inside the nearby galaxy M87 has a weight problem.

In fact, this galactic behemoth is obese.

With a mass of 6.6 billion suns, it is the biggest black hole in our cosmic neighborhood. “It’s almost on top of us, relatively speaking. Fifty million light-years — that’s our backyard effectively. To have one so large, that’s kind of extreme,” astronomer Karl Gebhardt, with the University of Texas at Austin, told Discovery News. The black hole’s mass was arrived at after Gebhardt’s team tracked the motions of the stars near the black hole using the Gemini North telescope in Hawaii. By analyzing the stars’ orbits, the mass of the black hole could be calculated.

Although it’s been known for some time that M87’s black hole might be slightly on the heavy side, 6.6 billion solar masses exceeds previous estimates.

Previously on Astroengine, I’ve discussed the exciting possibility of imaging a black hole’s event horizon. Radio astronomers have even modeled what they might see should a collection of telescopes participate in event horizon astronomy. Naturally, to see the shadow of an event horizon, the black hole a) needs to be massive, and b) relatively close. The first nearby supermassive black hole that comes to mind is our very own Sagittarius A* (Sag. A*) that camps out in the middle of the Milky Way. That would be a good place to point our first event horizon telescope, right?

Think again. Even before astronomers were able to pinpoint M87’s black hole mass, in 2009, researchers from the Max Planck Institute and University of Texas had estimated M87’s mass to be 6.4 billion suns. Although M87 is a whopping 2,000 times further away from Earth than Sag. A*, due to its mass, the M87 supermassive black hole event horizon shadow should appear bigger in the sky than Sag. A*’s. Today’s announcement is bound to stimulate efforts in the quest to directly image a black hole’s event horizon for the first time.

“Right now we have no evidence that an object is a black hole. Within a few years, we might be able to image the shadow of the event horizon,” Gebhardt added.

For more on today’s news, read Irene Klotz’s report on Discovery News: “Obese Black Hole Lurks in Our Cosmic Backyard

Star Birth Dominates Energy Production in Ultra-Luminous Galaxies

Artists impression of an ultra-luminous galaxy heating the surrounding dust (JAXA/ISAS/LIRA)
Artists impression of an ultra-luminous galaxy heating the surrounding dust (JAXA/ISAS/LIRA)

In the early 1980’s, NASA’s Infrared Astronomical Satellite (IRAS) detected a number of unknown objects lurking in the depths of the cosmos.

At the time, these IRAS objects stirred speculation in the press. Were the infrared signals being emitted by comets inside the Solar System? Or were they failed stars (brown dwarfs) lurking beyond the orbit of Pluto? The latter theory spawned the idea that the hunt for Planet X was back on (stoking the smoldering conspiracy embers of the flawed doomsday theory that Nibiru is coming to get us). Alas, it was neither, these intense infrared signals were coming from much, much further away.

It turned out that the infrared emissions were being generated by galaxies that, bizarrely, had little optical signal. Although a high proportion of them were known to be interacting galaxies (i.e. they were colliding with other galaxies), the exact energy mechanism driving their emissions was not known.

Ultra-luminous galaxies have the luminocity of a trillion Suns, whereas our galaxy has the luminosity of a pedestrian ten billion Suns. Obviously, ultra-luminous galaxies are different animals to the Milky Way, but a galaxy is a galaxy and the energy sources are similar whether they are ultra-luminous or not. It would appear that the only difference is how active the galaxy is.

The first obvious energy source in a galaxy is star formation; the more stars that are forming, the brighter the galaxy. Secondly — as with our galaxy — the central supermassive black hole’s accretion rate contributes to the galaxy’s energy budget; the more matter being accreted by the black hole, the more energy is being generated (and therefore the brighter the galaxy).

So, when observing these ultra-luminous galaxies, surely it should be an easy task to work out where all this energy is coming from? Actually, this isn’t the case, astronomers are having a difficult job in understanding the nature of IRAS galaxies and the reason for this comes from the source of the infrared emissions. Galactic dust is being heated by the energy source, but this dust obscures the source of this heating (it is opaque to optical wavelengths).

Smithsonian Astrophysical Observatory (SAO) researcher Guido Risaliti and his team have been analyzing Spitzer data to try to characterize the infrared emissions from 71 ultra-luminous galaxies. Using a “dust emission diagnostic technique,” the team have deduced that approximately 70% of the galaxies have active nuclei (i.e. their supermassive black holes have high accretion rates). Although most of the galactic nuclei are active, it is star formation that dominates the energy production in two-thirds of the galaxies. Also, these account for the highest fraction of the brightest galaxies.

This is a significant finding as it demonstrates how a galaxy reacts when it interacts with another galaxy. It would appear that the black hole in the core of the galactic bulge is kick-started during the massive gravitational interaction, boosting energy output as it eats more matter. The interaction also boosts star birth and this energy source becomes a dominant factor. Both energy sources heat up interstellar dust, making the galaxy glow in infrared wavelengths while optical light is masked.

Source: SAO (Harvard)

Unexpectedly Large Black Holes and Dark Matter

The M87 black hole blasts relativistic plumes of gas 5000 ly from the centre of the galaxy (NASA)
The M87 black hole blasts relativistic plumes of gas 5000 ly from the centre of the galaxy (NASA)

I just spent 5 minutes trying to think up a title to this post. I knew what I wanted to say, but the subject is so “out there” I’m not sure if any title would be adequate. As it turns out, the title doesn’t really matter, so I opted for something more descriptive…

So what’s this about? Astronomers think they will be able to “see” a supermassive black hole in a galaxy 55 million light years away? Surely that isn’t possible. Actually, it might be.

When Very Long Baseline Interferometry is King

Back in June, I reported that radio astronomers may be able to use a future network of radio antennae as part of a very long baseline interferometry (VLBI) campaign. With enough observatories, we may be able to resolve the event horizon of the supermassive black hole lurking at the centre of the Milky Way, some 26,000 light years away from the Solar System.

The most exciting thing is that existing sub-millimeter observations of Sgr. A* (the radio source at the centre of our galaxy where the 4 million solar mass black hole lives) suggest there is some kind of active structure surrounding the black hole’s event horizon. If this is the case, a modest 7-antennae VLBI could observe dynamic flares as matter falls into the event horizon.

It would be a phenomenal scientific achievement to see a flare-up after a star is eaten by Sgr. A*, or to see the rotation of a possibly spinning black hole event horizon.

All of this may be a possibility, and through a combination of Sgr. A*’s mass and relatively close proximity to Earth, our galaxy’s supermassive black hole is predicted to have the largest apparent event horizon in the sky.

Or does it?

M87 Might be a Long Way Away, But…

As it turns out, there could be another challenger to Sgr. A*’s “largest apparent event horizon” crown. Sitting in the centre of the active galaxy called M87, 55 million light years away (that’s over 2,000 times further away than Sgr. A*), is a black hole behemoth.

M87’s supermassive black hole consumes vast amounts of matter, spewing jets of gas 5,000 light years from the core of the giant elliptical galaxy. And until now, astronomers have underestimated the size of this monster.

Karl Gebhardt (Univ. of Texas at Austin) and Thomas Jens (Max Planck Institute for Extraterrestrial Physics in Garching, Germany) took another look at M87 and weighed the galaxy by sifting through observational data with a supercomputer model. This new model accounted for the theorized halo of invisible dark matter surrounding M87. This analysis yielded a shocking result; the central supermassive black hole should have a mass of 6.4 billion Suns, double the mass of previous estimates.

Therefore, the M87 black hole is around 1,600 times more massive than our galaxy’s supermassive black hole.

A Measure for Dark Matter?

Now that the M87 black hole is much bigger than previously thought, there’s the tantalizing possibility of using the proposed VLBI to image M87’s black hole as well as Sgr. A*, as they should both have comparable event horizon dimensions when viewed from Earth.

Another possibility also comes to mind. Once an international VLBI is tested and proven to be an “event horizon telescope,” if we are able to measure the size of the M87 black hole, and its mass is confirmed to be in agreement with the Gebhardt-Jens model, perhaps we’ll have one of the first indirect methods to measure the mass of dark matter surrounding a galaxy…

Oh yes, this should be good.

UPDATE! How amiss of me, I forgot to include the best black hole tune ever:

Publication: The Black Hole Mass, Stellar Mass-to-Light Ratio, and Dark Matter Halo in M87, Karl Gebhardt et al 2009 ApJ 700 1690-1701, doi: 10.1088/0004-637X/700/2/1690.
Via: New Scientist

Mystery Blob Detected 12.9 Billion Light Years Away

The Himiko object, the most massive object ever discovered in the early universe (M. Ouchi et al.)

Take a good look, this is one of the most mysterious, massive objects ever discovered in the cosmos. We don’t really know what it is, but this thing is huge, spanning 55,000 light years across (the approximate radius of our Milky Way). What makes this all the more intriguing is the fact that this object formed only 800 million years after the Big Bang and it is 10 times more massive than the next biggest object observed in the early Universe. But what is it?
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