Artistic view of a radiating black hole. Credit: NASA
A new paper has been posted on the arxiv (a repository of research preprints) introducing the idea of a Planck star arising from a black hole. These hypothetical objects wouldn’t be a star in the traditional sense, but rather the light emitted when a black hole dies at the hands of Hawking radiation. The paper hasn’t been peer reviewed, but it presents an interesting idea and a possible observational test.
When a large star reaches the end of its life, it explodes as a supernova, which can cause its core to collapse into a black hole. In the traditional model of a black hole, the material collapses down into an infinitesimal volume known as a singularity. Of course this doesn’t take into account quantum theory.
Although we don’t have a complete theory of quantum gravity, we do know a few things. One is that black holes shouldn’t last forever. Because of quantum fluctuations near the event horizon of a black hole, a black hole will emit Hawking radiation. As a result, a black hole will gradually lose mass as it radiates. The amount of Hawking radiation it emits is inversely proportional to its size, so as the black hole gets smaller it will emit more and more Hawking radiation until it finally radiates completely away.
Because black holes don’t last forever, this has led Stephen Hawking and others to propose that black holes don’t have an event horizon, but rather an apparent horizon. This would mean the material within a black hole would not collapse into a singularity, which is where this new paper comes in.
Diagram showing how matter approaches Planck density. Credit: Carlo Rovelli and Francesca Vidotto
The authors propose that rather than collapsing into a singularity, the matter within a black hole will collapse until it is about a trillionth of a meter in size. At that point its density would be on the order of the Planck density. When the the black hole ends its life, this “Planck star” would be revealed. Because this “star” would be at the Planck density, it would radiate at a specific wavelength of gamma rays. So if they exist, a gamma ray telescope should be able to observe them.
Just to be clear, this is still pretty speculative. So far there isn’t any observational evidence that such a Planck star exists. It is, however, an interesting solution to the paradoxical side of black holes.
This picture was created from images forming part of the Digitized Sky Survey 2. It shows the rich region of sky around the young open star cluster NGC 2547 in the southern constellation of Vela (The Sail). Credit:
ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin
Black holes are big influencers for the early universe; these singularities that were close to ancient stars heated up gas and affected star formation across the cosmos. A new study, however, says that heating happened later than previously thought.
“It was previously believed that the heating occurred very early, but we discovered that this standard picture delicately depends on the precise energy with which the X-rays come out,” stated Rennan Barkana, a co-author of the paper who is an astronomer at Tel Aviv University.
“Taking into account up-to-date observations of nearby black-hole binaries changes the expectations for the history of cosmic heating. It results in a new prediction of an early time (when the universe was only 400 million years old) at which the sky was uniformly filled with radio waves emitted by the hydrogen gas.”
These so-called “black-hole binaries” are star pairs where the larger star exploded into a supernova and left behind a black hole. The strong gravity then yanked gas away from the stellar companion, emitting X-rays in the process. The radiation, as it flows across the universe, is cited as the factor behind gas heating in other parts of space.
Artist rendering of a supermassive black hole. Credit: NASA / JPL-Caltech.
A recent paper by Stephen Hawking has created quite a stir, even leading Nature News to declare there are no black holes. As I wrote in an earlier post, that isn’t quite what Hawking claimed. But it is now clear that Hawking’s claim about black holes is wrong because the paradox he tries to address isn’t a paradox after all.
It all comes down to what is known as the firewall paradox for black holes. The central feature of a black hole is its event horizon. The event horizon of a black hole is basically the point of no return when approaching a black hole. In Einstein’s theory of general relativity, the event horizon is where space and time are so warped by gravity that you can never escape. Cross the event horizon and you are forever trapped.
This one-way nature of an event horizon has long been a challenge to understanding gravitational physics. For example, a black hole event horizon would seem to violate the laws of thermodynamics. One of the principles of thermodynamics is that nothing should have a temperature of absolute zero. Even very cold things radiate a little heat, but if a black hole traps light then it doesn’t give off any heat. So a black hole would have a temperature of zero, which shouldn’t be possible.
Then in 1974 Stephen Hawking demonstrated that black holes do radiate light due to quantum mechanics. In quantum theory there are limits to what can be known about an object. For example, you cannot know an object’s exact energy. Because of this uncertainty, the energy of a system can fluctuate spontaneously, so long as its average remains constant. What Hawking demonstrated is that near the event horizon of a black hole pairs of particles can appear, where one particle becomes trapped within the event horizon (reducing the black holes mass slightly) while the other can escape as radiation (carrying away a bit of the black hole’s energy).
While Hawking radiation solved one problem with black holes, it created another problem known as the firewall paradox. When quantum particles appear in pairs, they are entangled, meaning that they are connected in a quantum way. If one particle is captured by the black hole, and the other escapes, then the entangled nature of the pair is broken. In quantum mechanics, we would say that the particle pair appears in a pure state, and the event horizon would seem to break that state.
Artist visualization of entangled particles. Credit: NIST.
Last year it was shown that if Hawking radiation is in a pure state, then either it cannot radiate in the way required by thermodynamics, or it would create a firewall of high energy particles near the surface of the event horizon. This is often called the firewall paradox because according to general relativity if you happen to be near the event horizon of a black hole you shouldn’t notice anything unusual. The fundamental idea of general relativity (the principle of equivalence) requires that if you are freely falling toward near the event horizon there shouldn’t be a raging firewall of high energy particles. In his paper, Hawking proposed a solution to this paradox by proposing that black holes don’t have event horizons. Instead they have apparent horizons that don’t require a firewall to obey thermodynamics. Hence the declaration of “no more black holes” in the popular press.
But the firewall paradox only arises if Hawking radiation is in a pure state, and a paper last month by Sabine Hossenfelder shows that Hawking radiation is not in a pure state. In her paper, Hossenfelder shows that instead of being due to a pair of entangled particles, Hawking radiation is due to two pairs of entangled particles. One entangled pair gets trapped by the black hole, while the other entangled pair escapes. The process is similar to Hawking’s original proposal, but the Hawking particles are not in a pure state.
So there’s no paradox. Black holes can radiate in a way that agrees with thermodynamics, and the region near the event horizon doesn’t have a firewall, just as general relativity requires. So Hawking’s proposal is a solution to a problem that doesn’t exist.
What I’ve presented here is a very rough overview of the situation. I’ve glossed over some of the more subtle aspects. For a more detailed (and remarkably clear) overview check out Ethan Seigel’s post on his blog Starts With a Bang! Also check out the post on Sabine Hossenfelder’s blog, Back Reaction, where she talks about the issue herself.
Orbiting near a moving black hole doesn't seem like the safest mode of transportation, but time dilation might make it worth the risk. Credit: NAOJ
If you could get a good look at the environment around a supermassive black hole — which is a black hole often found in the center of the galaxy — what factors would make that black hole keep going?
A Japanese study revealed that at least one of these black holes stay “active and luminous” by gobbling up nearby material, but notes that only a few of the observed galaxies that are merging have these types of black holes. This must mean something unique arises in the environment near the black hole to get it going, the researchers say. What that is, though, is still poorly understood.
Supermassive black holes, defined as black holes that have a million times the mass of the sun or more, reside in galaxy centers. “The merger of gas-rich galaxies with SMBHs [supermassive black holes] in their centers not only causes active star formation, but also stimulates mass accretion onto the existing SMBHs,” stated a press release from the Subaru Telescope.
“When material accretes onto a SMBH, the accretion disk surrounding the black hole becomes very hot from the release of gravitational energy, and it becomes very luminous. This process is referred to as active galactic nucleus (AGN) activity; it is different from the energy generation activity by nuclear fusion reactions within stars.”
Figuring out how these types of activity vary would give a clue as to how galaxies come together, the researchers said, but it’s hard to see anything in action because of dust and gas blocking the view of optical telescopes. That’s why infrared observations come in so handy, because it makes it easier to peer through the debris. (You can see some examples from this research below.)
Examples of infrared K-band images of luminous, gas-rich, merging galaxies. Credit: NAOJ
The team (led by the National Astronomical Observatory of Japan’s Masatoshi Imanishi) used NAOJ’s Subaru’s Infrared Camera and Spectrograph (IRCS) and the telescope’s adaptive optics system in two bands of infrared. Researchers looked at 29 luminous gas-rich merging galaxies in the infrared and found “at least” one active supermassive black hole in all but one of the ones studied. However, only four of these galaxies merging had multiple, active black holes.
“The team’s results mean that not all SMBHs in gas-rich merging galaxies are actively mass accreting, and that multiple SMBHs may have considerably different mass accretion rates onto SMBHs,” Subaru stated.
The implication is more about the environment around a supermassive black hole must be understood to figure out how mass accretes. Knowing more about this will improve computer simulations of galaxy mergers, the researchers said.
Artist concept of matter swirling around a black hole. (NASA/Dana Berry/SkyWorks Digital)
Nature News has announced that there are no black holes. This claim is made by none other than Stephen Hawking, so does this mean black holes are no more? It depends on whether Hawking’s new idea is right, and on what you mean be a black hole. The claim is based on a new paper by Hawking that argues the event horizon of a black hole doesn’t exist.
The event horizon of a black hole is basically the point of no return when approaching a black hole. In Einstein’s theory of general relativity, the event horizon is where space and time are so warped by gravity that you can never escape. Cross the event horizon and you can only move inward, never outward. The problem with a one-way event horizon is that it leads to what is known as the information paradox.
Professor Stephen Hawking during a zero-gravity flight. Image credit: Zero G.
The information paradox has its origin in thermodynamics, specifically the second law of thermodynamics. In its simplest form it can be summarized as “heat flows from hot objects to cold objects”. But the law is more useful when it is expressed in terms of entropy. In this way it is stated as “the entropy of a system can never decrease.” Many people interpret entropy as the level of disorder in a system, or the unusable part of a system. That would mean things must always become less useful over time. But entropy is really about the level of information you need to describe a system. An ordered system (say, marbles evenly spaced in a grid) is easy to describe because the objects have simple relations to each other. On the other hand, a disordered system (marbles randomly scattered) take more information to describe, because there isn’t a simple pattern to them. So when the second law says that entropy can never decrease, it is say that the physical information of a system cannot decrease. In other words, information cannot be destroyed.
The problem with event horizons is that you could toss an object (with a great deal of entropy) into a black hole, and the entropy would simply go away. In other words, the entropy of the universe would get smaller, which would violate the second law of thermodynamics. Of course this doesn’t take into account quantum effects, specifically what is known as Hawking radiation, which Stephen Hawking first proposed in 1974.
The original idea of Hawking radiation stems from the uncertainty principle in quantum theory. In quantum theory there are limits to what can be known about an object. For example, you cannot know an object’s exact energy. Because of this uncertainty, the energy of a system can fluctuate spontaneously, so long as its average remains constant. What Hawking demonstrated is that near the event horizon of a black hole pairs of particles can appear, where one particle becomes trapped within the event horizon (reducing the black holes mass slightly) while the other can escape as radiation (carrying away a bit of the black hole’s energy).
Hawking radiation near an event horizon. Credit: NAU.
Because these quantum particles appear in pairs, they are “entangled” (connected in a quantum way). This doesn’t matter much, unless you want Hawking radiation to radiate the information contained within the black hole. In Hawking’s original formulation, the particles appeared randomly, so the radiation emanating from the black hole was purely random. Thus Hawking radiation would not allow you to recover any trapped information.
To allow Hawking radiation to carry information out of the black hole, the entangled connection between particle pairs must be broken at the event horizon, so that the escaping particle can instead be entangled with the information-carrying matter within the black hole. This breaking of the original entanglement would make the escaping particles appear as an intense “firewall” at the surface of the event horizon. This would mean that anything falling toward the black hole wouldn’t make it into the black hole. Instead it would be vaporized by Hawking radiation when it reached the event horizon. It would seem then that either the physical information of an object is lost when it falls into a black hole (information paradox) or objects are vaporized before entering a black hole (firewall paradox).
In this new paper, Hawking proposes a different approach. He argues that rather than instead of gravity warping space and time into an event horizon, the quantum fluctuations of Hawking radiation create a layer turbulence in that region. So instead of a sharp event horizon, a black hole would have an apparent horizon that looks like an event horizon, but allows information to leak out. Hawking argues that the turbulence would be so great that the information leaving a black hole would be so scrambled that it is effectively irrecoverable.
If Stephen Hawking is right, then it could solve the information/firewall paradox that has plagued theoretical physics. Black holes would still exist in the astrophysics sense (the one in the center of our galaxy isn’t going anywhere) but they would lack event horizons. It should be stressed that Hawking’s paper hasn’t been peer reviewed, and it is a bit lacking on details. It is more of a presentation of an idea rather than a detailed solution to the paradox. Further research will be needed to determine if this idea is the solution we’ve been looking for.
A composite image (X-ray and optical wavelengths) showing galaxy cluster RX J1532.9+3021 and the black hole at its center. Credit: X-ray: NASA/CXC/Stanford/J.Hlavacek-Larrondo et al, Optical: NASA/ESA/STScI/M.Postman & CLASH team
Got gas? The black hole in galaxy cluster RX J1532.9+3021 is keeping it all for itself and stopping trillions of stars from coming to be, according to new research. You can see data above from NASA’s Chandra X-ray Observatory (purple) and the Hubble Space Telescope (yellow).
The drama is taking place about 3.9 billion light-years from Earth, showing an extreme phenomenon that has been noted in other galaxies on smaller scales, Chandra officials stated.
“The large amount of hot gas near the center of the cluster presents a puzzle,” a statement read. “Hot gas glowing with X-rays should cool, and the dense gas in the center of the cluster should cool the fastest. The pressure in this cool central gas is then expected to drop, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. However, astronomers have found no such evidence for this burst of stars forming at the center of this cluster.”
Black hole with disc and jets visualization courtesy of ESA
What’s blocking the stars (according to data from Chandra and the National Science Foundation’s Karl G. Jansky Very Large Array) could be supersonic jets blasting from the black hole and shoving the gas in the area away, forming cavities on either side of the galaxy. These cavities, by the way, are immense — at 100,000 light-years across each, this makes them about as wide as our home galaxy, the Milky Way.
The big question is where that power came from. Perhaps the black hole is “ultramassive” (10 billion times of the sun) and has ample mass to shoot out those jets without eating itself up and producing radiation. Or, the black hole could be smaller (a billion times that of the sun) but spinning quickly, which would allow it to send out those jets.
Picture an entire star collapsed down into a gravitational singularity. An object with so much mass, compressed so tightly, that nothing, not even light itself can escape its grasp. It’s no surprise these objects have captured our imagination… and yet, I have a complaint.
The name “black hole” seems to have created something of a misunderstanding. And the images that show the gravitational well of a black hole don’t seem to help either.
From all the correspondence I get, I know many imagine these objects as magnificent portals to some other world or dimension. That they might be gateways which will take you off to adventures with beautiful glistening people in oddly tailored chainmail codpieces and bikinis.
So, if you were to jump into a black hole, where would you come out? What’s on the other side? Where do they take you to? Black holes don’t actually “go” anywhere. There isn’t an actual “hole” involved at all.
They’re massive black orbs in space with an incomprehensible gravitational field. We’re familiar with things that are black in color, like asphalt, or your favorite Cure shirt from the Wish tour that you’ve only ever hand-washed.
Black holes aren’t that sort of black. They’re black because even light, the fastest thing in the Universe, has given up trying to escape their immense gravity.
Let’s aim for a little context. Consider this. Imagine carrying an elephant around on your shoulders. Better yet, imagine wearing an entire elephant, like a suit. Now, let’s get off the couch and go for a walk. This what it would feel like if the gravity on Earth increased by a factor of 50. If we were to increase the force of gravity around your couch up to a level near the weakest possible black hole, it would be billions of times stronger than you would experience stuck under your elephant suit.
And so, if you jumped into a black hole, riding your space dragon, wearing maximus power gauntlets of punchiness and wielding some sort of ridiculous light-based melee weapon, you would then be instantly transformed … by those terrible tidal forces unravelling your body into streams of atoms… and then your mass would be added to the black hole.
Just so we’re clear on this, you don’t go anywhere. You just get added to the black hole.
It’s like wondering about the magical place you go if you jump into a trash compactor.
If you did jump into a black hole, your experience would be one great angular discomfort and then atomic disassembly. Here’s the truly nightmarish part. ..
As time distorts near the event horizon of a black hole, the outside Universe would watch you descend towards it more and more slowly. In theory, from their perspective it would take an infinite amount of time for you to become a part of the black hole. Even photons reflecting off your newly shaped body would be stretched out to the point that you would become redder and redder, and eventually, just fade away.
Artist concept of a view inside a black hole. Credit: April Hobart, NASA, Chandra X-Ray Observatory
Now that that is over with. Let’s clear up the matter of that diagram. Consider that image of a black hole’s gravity well. Anything with mass distorts space-time. The more mass you have, the more of a distortion you make….And black holes make bigger distortions than anything else in the Universe.
Light follows a straight line through space-time, even when space-time has been distorted into the maw of a black hole. When you get inside the black hole’s event horizon, all paths lead directly to the singularity, even if you’re a photon of light, moving directly away from it. It sounds just awful. The best news is that, from your perspective, it’s a quick and painful death for you and your space dragon.
So, if you had any plans to travel into a black hole, I urge you to reconsider. This isn’t a way to quickly travel to another spot in the Universe, or transcend to a higher form of consciousness. There’s nothing on the other side. Just disassembly and death.
If you’re looking for an escape to another dimension, might I suggest a good book instead?
The "Hand ( or Fist?) of God" nebula enshrouding pulsar PSR B1509-58. The upper red cloud structure is RCW 89. The image is a composite of Chandra observations (red & green), while NuSTAR observations are denoted in blue.
One star player in this week’s findings out of the 223rd meeting of the American Astronomical Society has been the Nuclear Spectroscopic Telescope Array Mission, also known as NuSTAR. On Thursday, researchers revealed some exciting new results and images from the mission, as well as what we can expect from NuSTAR down the road.
NuSTAR was launched on June 13th, 2012 on a Pegasus XL rocket deployed from a Lockheed L-1011 “TriStar” aircraft flying near the Kwajalein Atoll in the middle of the Pacific Ocean.
Part of a new series of low-cost missions, NuSTAR is the first of its kind to employ a space telescope focusing on the high energy X-ray end of the spectrum centered around 5-80 KeV.
Daniel Stern, part of the NuSTAR team at JPL Caltech, revealed a new X-ray image of the now-famous supernova remnant dubbed “The Hand of God.” Discovered by the Einstein X-ray observatory in 1982, the Hand is home to pulsar PSR B1509-58 or B1509 for short, and sits about 18,000 light years away in the southern hemisphere constellation Circinus. B1509 spins about 7 times per second, and the supernova that formed the pulsar is estimated to have occurred 20,000 years ago and would’ve been visible form Earth about 2,000 years ago.
A diagram of the NuSTAR satellite. (NASA/JPL/Caltech)
While the Chandra X-ray observatory has scrutinized the region before, NuSTAR can peer into its very heart. In fact, Stern notes that views from NuSTAR take on less of an appearance of a “Hand” and more of a “Fist”. Of course, the appearance of any nebula is a matter of perspective. Pareidolia litter the deep sky, whether it’s the Pillars of Creation to the Owl Nebula. We can’t help but being reminded of the mysterious “cosmic hand” that the Guardians of Oa of Green Lantern fame saw when they peered back at the moment of creation. Apparently, the “Hand” is also rather Simpson-esque, sporting only three “fingers!”
An diagram of the Hand of God. Credit: NASA/JPL/Caltech/McGill).
NuSTAR is the first, and so far only, focusing hard X-ray observatory deployed in orbit. NuSTAR employs what’s known as grazing incidence optics in a Wolter telescope configuration, and the concentric shells of the detector look like layers on an onion. NuSTAR also requires a large focal length, and employs a long boom that was deployed shortly after launch.
The hard X-ray regime that NuSTAR monitors is similar to what you encounter in your dentist’s office or in a TSA body scanner. Unlike the JEM-X monitor aboard ESA’s INTERGRAL or the Swift observatory, which have a broad resolution of about half a degree to a degree, NuSTAR has an unprecedented resolution of about 18 arc seconds.
The first data release from NuSTAR was in late 2013. NuSTAR is just begging to show its stuff, however, in terms of what researchers anticipate that it’s capable of.
“NuSTAR is uniquely able to map the Titanium-44 emission, which is a radioactive tracer of (supernova) explosion physics,” Daniel Stern told Universe Today.
NuSTAR will also be able to pinpoint high energy sources at the center of our galaxy. “No previous high-energy mission has had the imaging resolution of NuSTAR,” Stern told Universe Today. ”Our order-of-magnitude increase in image sharpness means that we’re able to map out that very rich region of the sky, which is populated by supernovae remnants, X-ray binaries, as well as the big black hole at the center of our Galaxy, Sagittarius A* (pronounced “A-star).”
NuSTAR identifies new black hole candidates (in blue) in the COSMOS field. The discoveries in the image above are overlayed on previous black holes spotted by Chandra in the same field, which are denoted in red and green. (Credit-NASA/JPL-Caltech/Yale University).
Yale University researcher Francesca Civano also presented a new image from NuSTAR depicting black holes that were previously obscured from view. NuSTAR is especially suited for this, gazing into the hearts of energetic galaxies that are invisible to observatories such Chandra or XMM-Newton. The image presented covers the area of Hubble’s Cosmic Evolution Survey, known as COSMOS in the constellation Sextans. In fact, Civano notes that NuSTAR has already seen the highest number of obscured black hole candidates to date.
“This is a hot topic in astronomy,” Civano said in a recent press release. “We want to understand how black holes grew and the degree to which they are obscured.”
To this end, NuSTAR researchers are taking a stacked “wedding cake” approach, looking at successively larger slices of the sky from previous surveys. These include looking at the quarter degree field of the Great Observatories Origins Deep Survey (GOOD-S) for 18 days, the two degree wide COSMOS field for 36 days, and the large four degree Swift-BAT fields for 40 day periods hunting for serendipitous sources.
Interestingly, NuSTAR has also opened the window on the hard X-ray background that permeates the universe as well. This peaks in the 20-30 KeV range, and is the combination of the X-ray emissions of millions of black holes.
“For several decades already, we’ve known what the sum total emission of the sky is across the X-ray regime,” Stern told Universe Today. “The shape of this cosmic X-ray background peaks strongly in the NuSTAR range. The most likely interpretation is that there are a large number of obscured black holes out there, objects that are hard to find in other energy bands. NuSTAR should find these sources.”
And NuSTAR may just represent the beginning of a new era in X-ray astronomy. ESA is moving ahead with its next generation flagship X-ray mission, known as Athena+, set to launch sometime next decade. Ideas abound for wide-field imagers and X-ray polarimeters, and one day, we may see a successor to NuSTAR dubbed the High-Energy X-ray Probe or (HEX-P) make it into space.
But for now, expect some great science out of NuSTAR, as it unlocks the secrets of the X-ray universe!
A composite x-ray and optical image of a dwarf galaxy showing the x-ray transcient in the inset. Credit-CFHT (Optical), NASA/CXC/University of Alabama/GSCF/UMD/W.P. Maksym, D.Donato et al.
This week, astronomers announced the detection of a rare event, a star being torn to shreds by a massive black hole in the heart of a distant dwarf galaxy. The evidence was presented Wednesday January 8th at the ongoing 223rd meeting of the American Astronomical Society being held this week in Washington D.C.
Although other instances of the death of stars at the hands of black holes have been witnessed before, Chandra may have been the first to document an intermediate black hole at the heart of a dwarf galaxy “in the act”.
The results span observations carried out by the space-based Chandra X-ray observatory over a period spanning 1999 to 2005. The search is part of an archival study of observations, and revealed no further outbursts after 2005.
“We can’t see the star being torn apart by the black hole, but we can track what happens to the star’s remains,” said University of Alabama’s Peter Maksym in a recent press release. A comparison of with similar events seen in larger galaxies backs up the ruling of “death by black hole.” A competing team led by Davide Donato also looked at archival data from Chandra and the Extreme Ultraviolet Explorer (EUVE), along with supplementary observations from the Canada-France-Hawaii Telescope to determine the brightness of the host galaxy, and gained similar results.
The dwarf galaxy in the Abell 1795 cluster that was observed has the name WINGS J134849.88+263557.5, or WINGS J1348 for short. The Abell 1795 cluster is about 800 million light years distant.
WINGS denotes the galaxy’s membership in the WIde-field Nearby Galaxy-cluster Survey, and the phone number-like designation is the galaxy’s position in the sky in right ascension and declination.
Like most galaxies associated with galaxy clusters, WINGS J1348 a dwarf galaxy probably smaller than our own satellite galaxy known as the Large Magellanic Cloud. The Abell 1795 cluster is located in the constellation Boötes, and WINGS J1348 has an extremely faint visual magnitude of +22.46.
An optical view of the Abell 1795 galaxy cluster. Credit- NASA/CFHT/D. Donato et al.
“Scientists have been searching for these intermediate mass black holes for decades,” NASA’s Davide Donato said in a recent press release “We have lots of evidence for small black holes and very big ones, but these medium-sized ones have been tough to pin down.”
Maksym notes in an interview with Universe Today that this isn’t the first detection of an intermediate-mass black hole, which are a class of black holes often dubbed the “mostly” missing link between stellar mass and super massive black holes.
The mass range for intermediate black holes is generally pegged at 100 to one million solar masses.
What makes the event witnessed by Chandra in WINGS J1348 special is that astronomers managed to capture a rare tidal flare, as opposed to a supermassive black hole in the core of an active galaxy.
A closeup view of the bright, long duration flare witnessed by Chandra pre-2005. Credit- NASA/CXC/University of Alabama/W.P. Maksym et al.
“Most of the time, black holes eat very little, so they can hide very well,” Maksym said in the AAS meeting on Wednesday.
This discovery pushes the limits on what we know of intermediate black holes. By documenting an observed number of tidal flare events, it can be inferred that a number of inactive black holes must be lurking in galaxies as well. The predicted number of tidal events that occur also have implications for the eventual detection of gravity waves from said mergers.
And more examples of these types of X-ray flare events could be waiting to be uncovered in the Chandra data as well.
“Chandra has taken quite a few pictures over the past 13+ years, and collaborators and I have an ongoing program to look for more tidal flares,” Maksym told Universe Today. “We’ve found one other this way, from a larger galaxy, and hope to find more. Abell 1795 was a particularly good place to look because as a calibration source, there were tons of pictures.”
Use of Chandra data was also ideal for the study because its spatial resolution allowed researchers to pinpoint an individual galaxy in the cluster. Maksym also notes that while it’s hard to get follow-up observations of events based on archival data, future missions dedicated to X-ray astronomy with wider fields of view may be able to scour the skies looking for such tidal flaring events.
The NuSTAR satellite was the latest X-Ray observatory to launch in 2012. NASA’s Extreme Ultraviolet Explorer picked up a strong ultraviolet source in 1998 right around the time of the tidal flare event, and ESA’s XMM-Newton satellite may have detected the event in 2000 as well.
This was also one of the smallest galaxies ever observed to contain a black hole. Maksym noted in Wednesday’s press conference that an alternative explanation could be a super-massive black hole in a tiny galaxy that just “nibbled” on a passing star, but said that new data from the Gemini observatory does not support this.
“It would be like looking into a dog house and finding a large ogre crammed in there,” Maksym said at Wednesday’s press conference.
This discovery provides valuable insight into the nature of intermediate mass black holes and their formation and behavior. What other elusive cosmological beasties are lying in wait to be discovered in the archives?
Congrats to Maksym and teams on this exciting new discovery, and the witnessing of a rare celestial event!
An exciting new discovery was unveiled early this week at the 223rd meeting of the American Astronomical Society being held in Washington D.C., when astronomers announced that a gravitational lens was detected for the first time at gamma-ray wavelengths.
The study was conducted using NASA’s Fermi Gamma Ray Space Telescope, and promises to open a new window on the universe, giving astrophysicists another tool to study the emission regions that exist near supermassive black holes.
But the hunt wasn’t easy. A gravitational lens occurs when a massive foreground object, such as a galaxy, bends the light from a distant background object. In the case of this study, researchers targeted a blazar known as B0218+357, a energetic source located 4.35 billion light years away in the direction of the constellation Triangulum.
Blazar and quasar sources are named using their respective coordinates in the sky. Think of “0218+357” as translating into “Right Ascension 2 Hours 18 Minutes, Declination +35.7 degrees north” in backyard astronomer-speak. A blazar is a compact form of quasar that results from a supermassive black hole at the heart of an active galaxy. The term blazar was first coined by Edward Spiegel in 1978. The first quasar discovered was 3C 273 in 1970, which was also later found to be a blazar. 3C 273 is visible in Virgo using a large backyard telescope.
A foreground spiral galaxy seen face on lies along our line of sight between our vantage point and B0218+357. At 4 billion light years distant, the two have the smallest angular separation of any gravitationally lensed system so far identified at less than a third of an arc second across.
“We began thinking about the possibility of making this observation a couple of years after Fermi launch, and all of the pieces finally came together in late 2012,” said Naval Research Laboratory astrophysicist and lead scientist on the study Teddy Cheung in a recent NASA Goddard Spaceflight Center press release.
Observations of the blazar suggested that it would be flaring in September 2012, making it a prime target for the study. In fact, B0218+357 was the brightest extra-galactic gamma-ray source at the time. Cheung was granted time spanning late September into October 2012 to use Fermi’s Large Area Telescope (LAT) instrument to study the blazar in outburst.
Fermi‘s LAT instrument doesn’t have the resolution possessed by radio and optical instruments to catch the blazar in single images. Instead, the team exploited a phenomenon known as the “delayed playback effect” to catch the blazar in action.
“One light path is slightly longer than the other, so when we detect flares in one image we try and catch them days later when they replay in the other image,” Said team member Jeff Scargle, astrophysicist based at NASA’s Ames Research Center.
Cheung presented the findings of the study Monday at the American Astronomical Society meeting, which included three distinct flaring episodes from the background blazar that demonstrated the tell-tale delayed playback events with a period spanning 11.46 days.
A Hubble Space Telescope image of the gravitational lensing of B0218+357. Credit: NASA/ESA and the Hubble Legacy Archive.
Follow-up observations in radio and optical wavelengths supported the key observations, and demonstrate that Fermi’s LAT imager did indeed witness the event. Interestingly, the delay for the gamma-rays from the lensed blazar takes about a day longer than radio waves to reach the Earth. B0218+357 is also about four times brighter in gamma-rays than in radio wavelengths.
This occurs because the gamma-rays are emanating from a slightly different region than radio waves generated by the blazar, and are taking a different path though the gravitational field of the foreground galaxy. This demonstrates that assets like Fermi can be used to probe the heart of the distant energetic galactic nuclei which harbor supermassive black holes. This opens the hot topic of gravitationally lensed blazars and their role in extra-galactic astronomy up to the gamma-ray spectrum, and gives cosmologists another gadget for their tool box.
“Over the course of a day, one of these flares can brighten the blazar by 10 times in gamma-rays but only 10 percent in visible light and radio, which tells us that the region emitting gamma-rays is very small compared to those emitting at lower energies,” Said Stockholm University team member Stefan Larsson in the recent press release.
Using the analysis of lensing systems at gamma-ray wavelengths will not only help to probe these enigmatic cosmological beasts, but it may also assist with refining the all-important Hubble Constant, which measures the rate at which the universe is expanding.
But Fermi may just beginning to show its stuff when it comes to hunting for extra-galactic sources. The really exciting breakthrough, researchers say, would be the discovery of an energetic extra-galactic source being lensed by a foreground galaxy in gamma-rays that hasn’t been seen been seen at other wavelengths. This recent finding has certainly demonstrated how Fermi can “see” these tell-tale flashes via a clever method. Expect more news in the coming years!
