Category: Galaxies

Our Supermassive Black Hole Is Slurping Down a Cool Hydrogen Smoothie

The world’s most powerful radio telescope is getting intimate with Sagittarius A*, revealing a never-before-seen component of its accretion flow

Artist impression of ring of cool, interstellar gas surrounding the supermassive black hole at the center of the Milky Way [NRAO/AUI/NSF; S. Dagnello]

As we patiently wait for the first direct image of the event horizon surrounding the supermassive black hole living in the core of our galaxy some 25,000 light-years away, the Atacama Millimeter/submillimeter Array (ALMA) has been busy checking out a previously unseen component of Sagittarius A*’s accretion flow.

Whereas the Event Horizon Telescope (EHT) will soon deliver the first image of our supermassive black hole’s event horizon, ALMA’s attention has recently been on a cool flow of gas that is orbiting just outside the event horizon, before being consumed. (The EHT delivered its first historic image on April 10, not of the supermassive black hole in our galaxy, but of the gargantuan six-billion solar mass monster in the heart of the giant elliptical galaxy, Messier 87, 50 million light-years away.)

While this may not grab the headlines like the EHT’s first image (of which ALMA played a key role), it remains a huge mystery as to how supermassive black holes pile on so much mass and how they consume the matter surrounding them. So, by zooming in on the reservoir of material that accumulates near Sagittarius A* (or Sgr A*), astronomers can glean new insights as to how supermassive black holes get so, well, massive, and how their growth relates to galactic evolution.

While Sgr A* isn’t the most active of black holes, it is feeding off limited rations of interstellar matter. It gets its sustenance from a disk of plasma, called an accretion disk, starting immediately outside its event horizon—the point at which nothing, not even light, can escape a black hole’s gravitational grasp—and ending a few tenths of a light-year beyond. The tenuous, yet extremely hot plasma (with searing temperatures of up to 10 million degrees Kelvin) close to the black hole has been well studied by astronomers as these gases generate powerful X-ray radiation that can be studied by space-based X-ray observatories, like NASA’s Chandra. However, the flow of this plasma is roughly spherical and doesn’t appear to be rotating around the black hole as an accretion disk should.

Cue a cloud of “cool” hydrogen gas: at a temperature of around 10,000K, this cloud surrounds the black hole at a distance of a few light-years. Until now, it’s been unknown how this hydrogen reservoir interacts with the black hole’s hypothetical accretion disk and accretion flow, if at all.

ALMA is sensitive to the radio wave emissions that are generated by this cooler hydrogen gas, and has now been able to see how Sgr. A* is slurping matter from this vast hydrogen reservoir and pulling the cooler gas into its accretion disk—a feature that has, until now, been elusive to our telescopes. ALMA has basically used these faint radio emissions to act as a tracer as the cool gas mingles with the accretion disk, revealing its rotation and the location of the disk itself.

“We were the first to image this elusive disk and study its rotation,” said Elena Murchikova, a member in astrophysics at the Institute for Advanced Study in Princeton, New Jersey, in a statement. “We are also probing accretion onto the black hole. This is important because this is our closest supermassive black hole. Even so, we still have no good understanding of how its accretion works. We hope these new ALMA observations will help the black hole give up some of its secrets.” Murchikova is the lead author of the study published in Nature on June 6.

ALMA image of the disk of cool hydrogen gas flowing around the supermassive black hole at the center of our galaxy. The colors represent the motion of the gas relative to Earth: the red portion is moving away, so the radio waves detected by ALMA are slightly stretched, or shifted, to the “redder” portion of the spectrum; the blue color represents gas moving toward Earth, so the radio waves are slightly scrunched, or shifted, to the “bluer” portion of the spectrum. Crosshairs indicate location of black hole [ALMA (ESO/NAOJ/NRAO), E.M. Murchikova; NRAO/AUI/NSF, S. Dagnello]

Located in the Chilean Atacama Desert, ALMA is comprised of 66 individual antennae that work as one interferometer to deliver observations of incredible precision. This is a bonus for these kinds of accretion studies, as ALMA has now probed right up to the edge of Sgr A*’s event horizon, only a hundredth of a light-year (or a few light-days) from the point of no return, providing incredible detail to the rotation of this cool disk of accreting matter. What’s more, the researchers estimate that ALMA is tracking only a minute quantity of cool gas, coming in at a total only a tenth of the mass of Jupiter.

A small quantity this may be (on galactic scales, at least), but it’s enough to allow the researchers to measure the Doppler shift of this dynamic flow, where some is blue-shifted (and therefore moving toward us) and some is red-shifted (as it moves away), allowing them to clock its orbital speed around the relentless maw of Sgr A*.

“We were able to shed new light on the accretion process around Sagittarius A*, which is a typical example of a class of black holes that have little to eat,” added Murchikova in a second statement. “The accretion behavior of these black holes is quite complex and, so far, not well understood.

“Our result is potentially important not only for our galaxy, but to any galaxy which has this type of underfed black hole in its heart. We hope that this cool disk will help us uncover more secrets of black holes and their behavior.”

Primordial Black Holes Probably Don’t Pack a Dark Matter Punch

Waiting for the Andromeda galaxy’s stars to twinkle may have extinguished hope for tiny black holes being a significant dark matter candidate

Should a black hole drift in front of a star, it could trigger a microlensing event, so astronomers set out to estimate the number of primordial black holes in Andromeda [Kavli IPMU]

Using the Andromeda galaxy as a huge detector, astronomers have taken a stab at seeing the unseeable — possibly disproving a hypothesis first put forward by the late Stephen Hawking 45 years ago.

According to Hawking’s work, the universe should be filled with black holes that were formed at the beginning of time, when the universe was a chaotic soup of energy just after the Big Bang. Known as “primordial” black holes, these ancient objects are hypothesized to invisibly occupy modern galaxies, including our own, boosting their dark matter mass.

These black holes aren’t the supermassive monsters that lurk in the centers of most galaxies; they’re not even stellar-mass black holes, formed after massive stars go supernova. Primordial black holes are much smaller than that, having leaked most of their mass via Hawking radiation since their formation 13.8 billion years ago. They should, however, still have powerful gravitational effects on the space surrounding them and, in new research published last week in the journal Nature Astronomy, an international team of researchers have leveraged these hypothetical black holes’ space-time-warping powers to reveal their presence.

Or not, as it turns out.

Central to this study is the effect of microlensing. This astronomical method relies on an object passing between us and a distant star. It has been used to great effect when detecting distant exoplanets, or rogue brown dwarfs wandering through interstellar space. Should one of these objects drift directly in front of a star, its gravitational field can create a magnification effect that briefly brightens the star’s light. The gravitational field creates a natural “lens” out of space-time itself, a prediction that arises from Einstein’s general relativity.

The effect of gravitational microlensing on a star in the Andromeda galaxy should a primordial black hole drift in front [Kavli IPMU]

It stands to reason that even though primordial black holes don’t generate any light themselves, if you stare at at entire galaxy for long enough, you should see a lot of twinkling stars, or microlensing events caused by the hypothetical swarm of primordial black holes the galaxy should contain. Count the number of events, and you can take a statistical stab the total number of primordial black holes in a galaxy like Andromeda, thereby providing an estimate as to how much of the universe’s missing dark matter mass is made up from these objects.

Using the power of the Subaru telescope in Hawaii, the researchers put this to the test, capturing 190 consecutive images of Andromeda over seven hours during one night with the observatory’s Hyper Suprime-Cam digital camera. If Hawking’s theory held, the telescope should have recorded approximately 1,000 microlensing events caused by primordial black holes with a mass of less than our moon drifting in front of Andromeda’s stars. Alas, only one microlensing event was detected that night. From this observation campaign alone, the researchers estimate that primordial black holes make up no more than 0.1 percent of the total dark matter mass in our universe.

Although this elegant study doesn’t necessarily disprove the existence of primordial black holes — one single event is interesting, but not compelling — it does put a wrench in the idea that they dominate the mass holed up in dark matter. So, the quest to understand the nature of dark matter grinds on and, with the help of this study, astronomers have now narrowed down the search by removing primordial black holes from the dark matter equation.

‘Crasher Asteroids’ Photobomb Hubble’s Deep Gaze Into the Universe

asteroid-trails
NASA, ESA, and B. Sunnquist and J. Mack (STScI)

Like the infamous “Crasher Squirrel” that launched one of the most prolific memes in online history, “crasher asteroids” have photobombed the Hubble Space Telescope’s otherwise uninterrupted view of the ancient universe.

While carrying out its Frontier Fields survey of a random postage stamp-sized part of the sky in the direction of the galaxy cluster Abell 370, Hubble imaged many galaxies located at different distances over different epochs in time.

Visible in the observation are elliptical galaxies and spiral galaxies. Many are bright and bluish, but the vast majority are dim and reddish. The reddest blobs are the most distant galaxies in our observable universe; their light has been stretched (red-shifted) after traveling for billions of years through an expanding cosmos. These galaxies are the most ancient galaxies that formed within a billion years after the Big Bang.

But mixed in with this Hubble view of ancient light are bright arcs and dashes — tracks carved out by the rocky junk in our own solar system that is drifting in Hubble’s field of view, located a mere 160 million miles from Earth (on average). It’s sobering to think that the light from the reddest galaxies is nearly three times older than these asteroids.*

Abel 370 is located along the solar system’s ecliptic plane, around which the planets orbit the sun and the majority of asteroids in the asteroid belt between Mars and Jupiter are located. So, like looking through a swarm of bees, Hubble has captured the trails of asteroids in the foreground.

The trails themselves are created not by the motion of the asteroids, however, but by the motion of Hubble. While fixing its gaze on distant galaxies for hours at a time as it orbits Earth, Hubble’s position changes and, through an observational effect known as parallax, the positions of those asteroids appear to trace an arc when compared with the stationary background of galaxies billions of light-years distant.

As Hubble scanned its field of view, it revealed 20 asteroid trails, seven of which are unique objects (some of the asteroid trails were repeated observations of the same object, just captured at different times in Hubble’s orbit). Only two of these asteroids were previously discovered, the other five are newly discovered objects that were too faint for other observatories to detect.

So it goes to show that photobombing asteroids are useful for science and, though Hubble was observing the most distant objects in the cosmos, it was able to see a few of the rocks in our cosmic backyard.

*NOTE: Asteroids formed around the time our solar system first started creating planets, some 4.6 billion years ago. The most ancient galaxies are located over 13 billion light-years away, meaning the ancient light from those galaxies was produced 13 billion years ago.

Friday Flashback: Banff Ground Squirrel Witnessed Apollo 11 Landing (2009)

Buzz Aldrin poses for Armstrong's camera in 1969. Little did the astronauts realize... they were being watched... (NASA/NatGeo/Ian O'Neill)
Buzz Aldrin poses for Armstrong’s camera in 1969. Little did the astronauts realize… they were being watched… (NASA/NatGeo/Ian O’Neill)

Primordial Black Holes Might be Cosmic Gold Diggers

black-hole-gold
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.

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

green-bank
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

eso1229a
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.

discoveryint
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.”

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

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)

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“