Astronomy

What does it mean when we say that information is potentially recoverable from a black hole

What does it mean when we say that information is potentially recoverable from a black hole


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My understanding is that if the surface of a black hole is holographic, then information is potentially emitted from a black hole, say due to Hawking radiation or some other means.

What can say about this information? Is it physically possible and/or feasible that this type of emission would embed information about what went into it? Also, how does this measure up against the idea that the world lines inside the event horizon are completely disconnected from the outside?

I have some knowledge of the information paradox, but I was really hoping someone could explain it in simple terms or point me to a prior explanation along those lines.


The first thing to understand is that we have no actual knowledge of how information and black holes interact.

What we do have are theories that are well supported by experiment (General Relativity, which predicts Black Holes but which says nothing about information) and Quantum Mechanics (which says a lot about information (in this technical sense) but nothing about BHs.) We also have a variety of theories, none of which have any substantial experimental support, and all of which are incomplete (which means we don't know if there's actually a viable theory there -- all we have today is bits and pieces that look promising). One of the goals of all of these theories is to -- somehow -- meld GR and QM into a single coherent theory with greater explanatory power than the two separately.

It is very fair to say that some of the work which has been done to date which tries to link information and BHs is plausible and (at least) does not contradict any experimental evidence we have. And some of them (like what Hawking used in the prediction of Hawking radiation) are such a careful application of QM in the GR context that most physicists would be surprised if they turned out to be incorrect.

The bottom line is that GR and QM are both amazing theories which yet cannot be completely correct -- they must both be subsumed in some more encompassing theory. (Or at least everyone is convinced of that. I am too, BTW.)

Due to the mathematical underpinnings of QM and GR, physicists vaguely can see how some generalization of QM might, possibly be able to include GR someday. But virtually no one can see how GR could be extended to include QM. So the smart money -- just about all the money, actually -- is on extending QM in some way.

One of the most basic features of QM is that it is linear and preserves information (in a certain well-defined, but technical sense). If GR could be derived from some extension of QM, we'd expect that that extension of QM preserves information, and that GR also must preserve information.

On the face of it, GR by itself says that information which falls into a BH is lost. Zap. Gone. Never to return. Therefor finding ways to get GR to preserve information may be an important clue to the ultimate combined theory. And extensions of GR which preserve information seem more likely to be correct.

So the paradox is that BHs, which are predicted by our marvelously correct theory of gravity, GR, do not conserve information. But we have reasons to strongly suspect that BH built from the hypothetical gravitational extension of QM would preserve information. Something's wrong here!

One of the plausible theories that have been developed to resolve this says that Hawking radiation -- which seems very plausible, and which carries energy away from a BH in contradiction of vanilla GR -- might also carry the "lost" information away, eliminating the paradox.

Maybe.

But remember that there isn't any experimental evidence for any of this. It's all based on smart hard-working, competent scientists trying to use their brains and their intuition to guess what the undiscovered theory which merges GR and QM will predict and to turn it into consistent math. It's certainly better than a random-assed guess, but it is a far cry from established science.

Keep watching -- I hope that all this work will bear fruit and a real theory with experimental evidence behind it might emerge in our lifetimes.


Just to add to Mark's excellent answer, experimental verification of any information carried by Hawking radiation is not easy, and it may remain so indefinitely, even if we could visit a black hole in a spaceship to make up-close measurements.

Hawking radiation (if it exists) is extremely difficult to detect, even if you are near the black hole, which isn't a healthy place to be if the black hole is active. And of course the radiation from the matter in the accretion disk will totally swamp the Hawking radiation.

For example, the SMBH M87* emits Hawking radiation with a mean temperature of $9.5 imes 10^{-18}$ kelvin, at a luminosity of $2.13 imes 10^{-48}$ watts.

A stellar mass BH is warmer & brighter, but still way too dim for us to detect. Eg, a 10 solar mass BH emits at a temperature of around a nanokelvin, with a luminosity of $9 imes 10^{-31}$ watts.

I used this online Hawking radiation calculator to obtain those figures.


The many definitions of a black hole

Although black holes are objects of central importance across many fields of physics, there is no agreed upon definition for them, a fact that does not seem to be widely recognized. Physicists in different fields conceive of and reason about them in radically different, and often conflicting, ways. All those ways, however, seem sound in the relevant contexts. After examining and comparing many of the definitions used in practice, I consider the problems that the lack of a universally accepted definition leads to, and discuss whether one is in fact needed for progress in the physics of black holes. I conclude that, within reasonable bounds, the profusion of different definitions is in fact a virtue, making the investigation of black holes possible and fruitful in all the many different kinds of problems about them that physicists consider, although one must take care in trying to translate results between fields.


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Let's say a wad of strange matter hit the earth at whatever cosmic speed that it would be likely traveling at. How would it impact a solar body like the earth? What about just one strangelet? I keep thinking of this stuff being squished together in a neutron star, so I keep thinking of this unimaginably dense, hot, mystery particle. I read no two strangelets could occupy the same place at any given time, yet they bond directly together, so could a neutron star collapse into a singularity?

You'd think if this kind of matter could escape the confines of a neutron star, that we'd have observed more strange celestial bodies (like strange systems/universes?)

I love this kind of stuff. My own ignorance is the only thing that holds me back from learning more about things like strange matter! anon92830 June 30, 2010

I also am reading "Impact" by Douglas Preston and wanted to know if this strangelet matter that he refers to in his book really exist or did he make it up. I find out that there is a possibility that it does exist and guess what he did not make it up. zymurgyid May 21, 2010

I'm reading "Impact" by Douglas Preston and strange matter or a "strangelet" was used.

The description he gives is similar to the ones describing the Tunguska Event. A column of light reaching to the heavens and a blast wave that flattened a forest and a passing ship saw the same pillar of light going from the pacific ocean to the sky, which would roughly correspond to the entry point in Siberia.

The ongoing theory was that a micro-black hole passed through the earth. But it could also be a strangelet. anon57388 December 22, 2009

Jesus will sort it all out! Yeah! anon52472 November 14, 2009

This article mentions that strangelets can overwhelm "ordinary matter" with the strength of their gravitational fields. Is this meant to imply ordinary "particles" as well? I'm thinking of photons--I'm wondering if light can escape a strangelet's gravitational field. Thanks for reading! element92 January 9, 2009

anon 19848, your question as to the likelihood of any relationship between strangelet gravity wells and black holes is a valid one. A few caveats: since, as you said, even light is unable to escape from the gravitational field of a black hole after venturing past the event horizon, we are necessarily devoid of any information as to what exactly lies inside this "point of no return", since information is prevented from escaping in the form of photons secondly, strangelets, as they are currently understood, do not typically collapse to form black holes, i.e. they retain a measurable volume. So it could be said that the relationship between black holes and strangelets is simply their immense gravity, due to the densities involved. Though you should consider that black holes, since they have no volume, have infinite densities. They could be evolutionary partners, but this remains speculation. anon19848 October 20, 2008

Hi. I don't quite understand most of the things dealing in any field of science, but I was wondering since this strange matter stuff has these gravity wells then do they have any kind of relation with black holes. I mean we really don't know that much about black holes except that they are very dense and have such a gravitational force that light can't escape. that and I guess they are on a bigger scale then strangelets. Sorry I started rambling. I would like it if someone could help me understand this better. element92 September 13, 2008

anon17921, I assure you that my comment was the result of nothing more than a cynically minded sense of humour. In fact, I share your preference for a meticulously responsible approach to science, yet I remain mindful of the fact that there is a convincing reason why governments are reluctant to send their best epidemiologists to some obscure moon of Saturn and ask them to continue their "potentially" hazardous work there. The reason: Contrary to popular belief, they're not stupid. The only reason they don't completely dissolve the funding for these scientists is the possibility of their work ultimately paying (less than harmless) dividends. If it sounds cynical, it's because it is. Remember: I'm speaking from the point of view of world governments here. Would you expect anything else? anon17921 September 10, 2008

element92, I really hope you're kidding. I think we need to do these experiments much further from the only provable existence of sentient life. Nuts to the nuke lets figure out how to get to some intergalactic nowhere before we start tinkering with things that could make us disappear.

I'm not a Luddite, I just believe in a common sense approach to science. For instance- DNA should be manipulated in a completely isolated environment, like a moon. If we weren't busy investing in making germs and blowing each other up, we might already have that capability. element92 August 29, 2008

Well, quite obviously, science wouldn't be nearly as interesting if we didn't run the risk of anilhiliating the human race every once and a while (i.e., the nuclear bomb, bioengineering viruses, micro-black holes, etc.). anon14991 June 28, 2008

strange matter is not the necessarily the same thing as quark matter,

quark matter is simply mater composed of quark. strange matter is the name given to quark matter that has so-called strange quarks as part of its make-up. normal matter is composed of up and down quarks, but strange matter has strange quarks in addition to or replacing other types of quarks.

why would you even want to prove or disprove it when it could take over and ruin everything we have?


Scientists gear up to take a picture of a black hole

On Wednesday, Jan. 18, astronomers, physicists and scientists from related fields will convene in Tucson, Ariz. from across the world to discuss an endeavor that only a few years ago would have been regarded as nothing less than outrageous. The conference is organized by Dimitrios Psaltis, an associate professor of astrophysics at the University of Arizona's Steward Observatory, and Daniel Marrone, an assistant professor of astronomy at Steward Observatory.

"Nobody has ever taken a picture of a black hole," Psaltis said. "We are going to do just that."

"Even five years ago, such a proposal would not have seemed credible," added Sheperd Doeleman, assistant director of the Haystack Observatory at Massachusetts Institute of Technology (MIT), who is the principal investigator of the Event Horizon Telescope, as the project is dubbed. "Now we have the technological means to take a stab at it."

First postulated by Albert Einstein's Theory of General Relativity, the existence of black holes has since been supported by decades' worth of observations, measurements and experiments. But never has it been possible to directly observe and image one of these maelstroms whose sheer gravity exerts such cataclysmic power they twist and mangle the very fabric of space and time.

"Black holes are the most extreme environment you can find in the universe," Doeleman said.

The field of gravity around a black hole is so immense that it swallows everything in its reach not even light can escape its grip. For that reason, black holes are just that –emitting no light whatsoever, their "nothingness" blends into the black void of the universe.

So how does one take a picture of something that by definition is impossible to see?

"As dust and gas swirls around the black hole before it is drawn inside, a kind of cosmic traffic jam ensues," Doeleman explained. "Swirling around the black hole like water circling the drain in a bathtub, the matter compresses and the resulting friction turns it into plasma heated to a billion degrees or more, causing it to 'glow' – and radiate energy that we can detect here on Earth."

By imaging the glow of matter swirling around the black hole before it goes over the edge of the point of no return and plunges into the abyss of space and time, scientists can only see the outline of the black hole, also called its shadow. Because the laws of physics either don't apply to or cannot describe what happens beyond that point of no return from which not even light can escape, that boundary is called the Event Horizon.

"So far, we have indirect evidence that there is a black hole at the center of the Milky Way," Psaltis said. "But once we see its shadow, there will be no doubt."

Even though the black hole suspected to sit at the center of our galaxy is a supermassive one at four million times the mass of the Sun, it is tiny to the eyes of astronomers. Smaller than Mercury's orbit around the Sun, yet almost 26,000 light years away, it appears about the same size as a grapefruit on the moon.

"To see something that small and that far away, you need a very big telescope, and the biggest telescope you can make on Earth is to turn the whole planet into a telescope," Marrone said.

To that end, the team is connecting up to 50 radio telescopes scattered around the globe, including the Submillimeter Telescope (SMT) on Mt. Graham in Arizona, telescopes on Mauna Kea in Hawaii and the Combined Array for Research in Millimeter-wave Astronomy (CARMA) in California. The global array will include several radio telescopes in Europe, a 10-meter dish at the South Pole and potentially a 15-meter antenna atop a 15,000-foot peak in Mexico.

"In essence, we are making a virtual telescope with a mirror that is as big as the Earth," Doeleman said. "Each radio telescope we use can be thought of as a small silvered portion of a large mirror. With enough such silvered spots, one can start to make an image."

"The Event Horizon Telescope is not a first-light project, where we flip a switch and go from no data to a lot of data," he added. "Every year, we increase its capabilities by adding more telescopes, gradually sharpening the image we see of the black hole."

One crucial and eagerly expected key element about to join Event Horizon's global network of radio telescopes is the Atacama Large Millimeter Array, or ALMA, in Chile.

Comprising 50 radio antennas itself, ALMA will function as the equivalent of a dish that is 90 meters in diameter, and become what Doeleman called "a real game changer." "When ALMA comes online, it will double our resolution."

"The EHT will bring us as close to the edge of a black hole as we will ever come," the participating scientists wrote in a project summary.

"We will be able to actually see what happens very close to the horizon of a black hole, which is the strongest gravitational field you can find in the universe," Psaltis said. "No one has ever tested Einstein's Theory of General Relativity at such strong fields."

General Relativity predicts that the bright outline defining the black hole's shadow must be a perfect circle. According to Psaltis, whose research group specializes in Einstein's Theory of General Relativity, this provides an important test.

"If we find the black hole's shadow to be oblate instead of circular, it means Einstein's Theory of General Relativity must be flawed," he said. "But even if we find no deviation from general relativity, all these processes will help us understand the fundamental aspects of the theory much better."

Black holes remain among the least understood phenomena in the universe. Ranging in mass from a few times the mass of the Sun to billions, they appear to coalesce like drops of oil in water. Most if not all galaxies are now believed to harbor a supermassive black hole at their center, and smaller ones are scattered throughout. Our Milky Way is known to be home to about 25 smallish black holes ranging from 5 to 10 times the Sun's mass.

"What is great about the one in the center of the Milky Way is that is big enough and close enough," Marrone said. "There are bigger ones in other galaxies, and there are closer ones, but they're smaller. Ours is just the right combination of size and distance."

The reason astronomers rely on radio waves rather than visible or infrared light to spy on the black hole is two-fold: For one, observing the center of the Milky Way from the Earth requires peering right through the plane of the galaxy. Radio waves are able to penetrate thousands of light-years worth of stars, gas and dust obstructing the view. Secondly, combining optical telescopes into a virtual super-telescope would not be feasible, according to the researchers.

Only very recent technological advances have made it possible to not only record radio waves at just the right wavelengths where they don't interfere with water vapor in the atmosphere but also to ensure the ultra-precise timing necessary to combine observations from multiple telescopes thousands of miles apart into one exposure.

Each telescope will record its data onto hard drives, which will be collected and physically shipped to a central data processing center at MIT's Haystack Observatory.

Bringing together radio telescopes around the globe requires an equally global team effort.

"This is not only the usual international conference where people come from all over the world because they are interested in sharing their research," Psaltis said. "For the Event Horizon Telescope, we need the entire world to come together to build this instrument because it is as big as the planet. People are coming from all over the world because they have to work on it."


Ask Ethan: Why Is The Black Hole Information Loss Paradox A Problem?

Ilustration of a black hole and its surrounding, accelerating and infalling accretion disk. The . [+] initial and final states of black holes can be well-predicted, even if the loss-or-retention of information cannot, at present.

When it comes to the sciences, sometimes making two observations or measurements that appear to contradict each other is the best thing that could possibly happen. These apparent paradoxes help lead the field forward, and show us where to look for the solution. The fact that the night sky is dark, Olbers' paradox, wasn't resolved until the Big Bang came along. The Fermi paradox helps us understand how rare intelligent, spacefaring civilizations must truly be. And the black hole information loss paradox might truly be the key to unlocking quantum gravity. But is that last one really true? Gabe Eisenstein is skeptical, asking:

Why do physicists all seem to agree that the information loss paradox is a real problem? It seems to depend on determinism, which seems incompatible with QM.

Many people have a lot of preconceptions when it comes to the black hole information paradox, so let's give you the full version on why it's such a problem, and what its solution would mean.

In a Schwarzschild black hole, falling in leads you to the singularity, and darkness. Yet, whatever . [+] falls in contains information, while the black hole itself, at least in General Relativity, is defined only by its mass, charge, and angular momentum.

(Illustration) ESO, ESA/Hubble, M. Kornmesser

The first thing to recognize is that the black hole information paradox isn't so much about information the way we conceive of it. When we think about words in a printed book, the number of bits and bytes in a computer file, or the configurations and quantum properties of the particles comprising a system, we think of information as the full suite of things we'd need to know in order to reconstruct, from scratch, whatever it is we began with.

But this conventional definition of information isn't really a physical property that's easily measurable or quantifiable the way that, say, temperature is. Luckily for us, there is a physical property that can be defined as equivalent to information: entropy. Instead of thinking of entropy as a measure of disorder, we should think about entropy as the amount of "missing" information needed to determine what the specific microstate of your system is.

When a mass gets devoured by a black hole, the amount of entropy the matter has is determined by its . [+] physical properties. But inside a black hole, only properties like mass, charge, and angular momentum matter. This poses a big conundrum if the second law of thermodynamics must remain true.

Illustration: NASA/CXC/M.Weiss X-ray (top): NASA/CXC/MPE/S.Komossa et al. (L) Optical: ESO/MPE/S.Komossa (R)

There are rules that entropy must follow in this Universe. The second law of thermodynamics is one of the most inviolable ones: take any system you like, don't allow anything to enter or leave it, and its entropy will never spontaneously decrease.

Eggs don't spontaneously unscramble themselves, warm water never separates into hot and cold sections, and ashes don't reassemble into the shape of the object they were before they were burned. All of these would be an example of decreasing entropy, and this doesn't happen, in nature, on its own. Entropy can remain the same under most circumstance it increases but it can never return to a lower-entropy state.

A representation of Maxwell's demon, which can sort particles according to their energy on either . [+] side of a box.

Wikimedia Commons user Htkym

The only way to artificially decrease entropy is to pump energy into a system, "cheating" the second law by increasing the entropy external to the system by a larger amount than it decreases within your system. (Cleaning your house is one such example.) Put simply, entropy can never be destroyed.

So what happens, then, when a black hole feeds on matter? Let's go back to our original thought, and imagine throwing a book into a black hole. The only properties we know to assign to a black hole are very straightforward: mass, charge, and angular momentum. The book contains information, but when you throw it into a black hole, it only increases the black hole's mass. Originally, when it came to black holes, it was thought that their entropy must be zero. But if that were the case, allowing anything to fall into a black hole would always violate the second law of thermodynamics. And this, of course, cannot be.

The mass of a black hole is the sole determining factor of the radius of the event horizon, for a . [+] non-rotating, isolated black hole. For a long time, it was thought that black holes were static objects in the spacetime of the Universe.

So how, then, do you quantify the entropy of a black hole?

The idea for this can be traced back to John Wheeler, who was thinking about what happens to an object as it fall into a black hole from the point of view of an observer well outside the event horizon. From far away, someone falling in would appear to asymptotically approach the event horizon, turning redder and redder due to gravitational redshift, and taking an infinitely long time to reach the horizon, as relativistic time dilation took effect. The information, therefore, from whatever fell in would appear to be encoded on the surface area of the black hole itself.

Encoded on the surface of the black hole can be bits of information, proportional to the event . [+] horizon's surface area.

T.B. Bakker / Dr. J.P. van der Schaar, Universiteit van Amsterdam

This elegantly seems to solve the problem and make sense all at once. When something falls into a black hole, its mass increases. When its mass increases, so does its radius, and therefore, its surface area. The greater your surface area, the more information you can encode, the same way you can fit more strokes of a pen on a larger globe than a smaller one.

This implies that instead of an entropy of zero, a black hole's entropy is enormous! Even though an event horizon is relatively small compared to the size of the Universe, the amount of space it takes to encode a quantum bit is tiny, and therefore a tremendous amount of information can be encoded onto a black hole's surface. Entropy rises, information is conserved, and the laws of thermodynamics are obeyed. We can all go home.

Except, of course, for the paradox part.

The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even . [+] light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. Hawking's 1974 work was the first to demonstrate this, and it was arguably his greatest scientific achievement.

NASA DANA BERRY, SKYWORKS DIGITAL, INC.

You see, if black holes have an entropy, then they must also have a temperature. And like anything that has a temperature, it must radiate.

As Stephen Hawking famously demonstrated, black holes emit radiation of a particular (blackbody) spectrum and temperature, defined by the mass of the black hole that it's coming from. Over time, that emission of energy means that the black hole is losing mass, owing to Einstein's famous E = mc 2 if energy is being released, it has to come from somewhere, and that "somewhere" must be the black hole itself. Over time, the black hole will lose mass faster and faster, until in a brilliant flash of light far in the future, it evaporates entirely.

Against a seemingly eternal backdrop of everlasting darkness, a single flash of light will emerge: . [+] the evaporation of the final black hole in the Universe. This is the ultimate fate of every black hole: total evaporation.

But if the black hole evaporates into pure blackbody radiation, defined only by the black hole's mass, then what happens to all that information and all that entropy that was encoded on the event horizon of the black hole? You can't just destroy that information, can you?

That's the root of the black hole information paradox. Black holes must have a large entropy, that entropy includes all the information about what created the black hole, the information gets encoded on the surface of the event horizon, but as the black hole decays away via Hawking radiation, the event horizon disappears, leaving only radiation in its place. That radiation, as far as we understand it, is only dependent on a black hole's mass, not on anything else.

Anything that burns might appear to be destroyed, but everything about the pre-burned state is, in . [+] principle, recoverable, if we track everything that comes out of the fire. Public domain image.

A book of gibberish and a copy of the Count of Monte Cristo contain different amounts of information. Yet, if their masses were identical, and we threw them into identical black holes, we'd eventually expect equivalent Hawking radiation to emerge from them. To an outside observer, it looks like information gets destroyed, and based on what we know about entropy, that shouldn't be possible. That would, in fact, violate the 2nd law of thermodynamics.

If you burned those two identically-sized books instead, the patterns of ink on the paper, the variations in molecular structures, and other minute differences all contain information that could allow you to reconstruct the information within them. The information may be scrambled, but it's not lost. The black hole information paradox, however, is a real problem. Once a black hole evaporates, that initial information has left no trace anywhere in our observable Universe.

The simulated decay of a black hole not only results in the emission of radiation, but the decay of . [+] the central orbiting mass that keeps most objects stable. Black holes are not static objects, but rather change over time. However, black holes formed of different materials should have different information encoded on their event horizons.

We may not have the answers to this paradox yet, but it represents a real problem for physics. Still, we can envision what the solution to this might look like. As far as we understand it, one of two things must be happening:

  1. Either information is truly destroyed somehow when a black hole evaporates, teaching us that there are new physical rules and laws in place for black hole evaporation,
  2. Or the radiation that's emitted somehow contains this information, meaning that there's more to Hawking radiation than the calculations we've done so far imply.

For the real black holes that exist or get created in our Universe, we can observe the radiation . [+] emitted by their surrounding matter, but not the Hawking radiation theorized to be spontaneously emitted from outside their event horizons. We have only ever successfully measured the predicted Hawking effect for black hole analogue systems in fluid dynamics and condensed matter systems.

LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

Most people working on this problem think that somehow, there must be a way that the information encoded on the surface of the black hole imprints itself on the outgoing radiation. How that happens, though, is something no one understands.

Is it due to the fact that information on the black hole's surface applies quantum corrections to the purely thermal Hawking radiation state?

It's tempting to think so, but it's unproven. As it stands, there are a myriad of hypothesized solutions to the paradox, but none have been proven.

When you fall into a black hole or simply get very close to the event horizon, its size and scale . [+] appear much larger than the actual size. To an outside observer watching you fall in, your information would get encoded on the event horizon. What happens to that information as the black hole evaporates is still unanswered.

Andrew Hamilton / JILA / University of Colorado

The black hole information paradox is agnostic about whether the nature of the quantum Universe is deterministic or non-deterministic, which quantum interpretation you choose, whether there are hidden variables or not, or many other aspects of the nature of reality. We do not yet know whether there are more dimensions than the four we presently know of, and while many proposed solutions invoke the holographic principle, it is uncertain whether that plays any role in whatever the resolution of the paradox truly turns out to be.

Many ideas are compelling or interesting, but these are merely ideas the paradox remains unresolved. There is no clear solution. Despite the fact that pretty much everyone agrees that the solution ought to have information encoded in the outgoing radiation, no one yet knows how to arrive at it. Until we can figure out how — or if — information is preserved in black hole decays, this puzzle will remain a great paradox of our time.


WISE Findings Poke Hole in Black Hole 'Doughnut' Theory

A survey of more than 170,000 supermassive black holes, using NASA's Wide-field Infrared Survey Explorer (WISE), has astronomers reexamining a decades-old theory about the varying appearances of these interstellar objects.

The unified theory of active, supermassive black holes, first developed in the late 1970s, was created to explain why black holes, though similar in nature, can look completely different. Some appear to be shrouded in dust, while others are exposed and easy to see.

The unified model answers this question by proposing that every black hole is surrounded by a dusty, doughnut-shaped structure called a torus. Depending on how these "doughnuts" are oriented in space, the black holes will take on various appearances. For example, if the doughnut is positioned so that we see it edge-on, the black hole is hidden from view. If the doughnut is observed from above or below, face-on, the black hole is clearly visible.

However, the new WISE results do not corroborate this theory. The researchers found evidence that something other than a doughnut structure may, in some circumstances, determine whether a black hole is visible or hidden. The team has not yet determined what this may be, but the results suggest the unified, or doughnut, model does not have all the answers.

"Our finding revealed a new feature about active black holes we never knew before, yet the details remain a mystery," said Lin Yan of NASA's Infrared Processing and Analysis Center (IPAC), based at the California Institute of Technology in Pasadena. "We hope our work will inspire future studies to better understand these fascinating objects."

Yan is the second author of the research accepted for publication in the Astrophysical Journal. The lead author is post-doctoral researcher, Emilio Donoso, who worked with Yan at IPAC and has since moved to the Instituto de Ciencias Astronómicas, de la Tierra y del Espacio in Argentina. The research also was co-authored by Daniel Stern at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, and Roberto Assef of Universidad Diego Portales in Chile and formerly of JPL.

Every galaxy has a massive black hole at its heart. The new study focuses on the "feeding" ones, called active, supermassive black holes, or active galactic nuclei. These black holes gorge on surrounding gas material that fuels their growth.

With the aid of computers, scientists were able to pick out more than 170,000 active supermassive black holes from the WISE data. They then measured the clustering of the galaxies containing both hidden and exposed black holes -- the degree to which the objects clump together across the sky.

If the unified model was true, and the hidden black holes are simply blocked from view by doughnuts in the edge-on configuration, then researchers would expect them to cluster in the same way as the exposed ones. According to theory, since the doughnut structures would take on random orientations, the black holes should also be distributed randomly. It is like tossing a bunch of glazed doughnuts in the air -- roughly the same percentage of doughnuts always will be positioned in the edge-on and face-on positions, regardless of whether they are tightly clumped or spread far apart.

But WISE found something totally unexpected. The results showed the galaxies with hidden black holes are more clumped together than those of the exposed black holes. If these findings are confirmed, scientists will have to adjust the unified model and come up with new ways to explain why some black holes appear hidden.

"The main purpose of unification was to put a zoo of different kinds of active nuclei into a single umbrella," said Donoso. Now, that has become increasingly complex to do as we dig deeper into the WISE data."

Another way to understand the WISE results involves dark matter. Dark matter is an invisible substance that dominates matter in the universe, outweighing the regular matter that makes up people, planets and stars. Every galaxy sits in the center of a dark matter halo. Bigger halos have more gravity and, therefore, pull other galaxies toward them.

Because WISE found that the obscured black holes are more clustered than the others, the researchers know those hidden black holes reside in galaxies with larger dark matter halos. Though the halos themselves would not be responsible for hiding the black holes, they could be a clue about what is occurring.

"The unified theory was proposed to explain the complexity of what astronomers were seeing," said Stern. "It seems that simple model may have been too simple. As Einstein said, models should be made 'as simple as possible, but not simpler.'"

Scientists still are actively combing public data from WISE, put into hibernation in 2011 after scanning Earth's entire sky twice. WISE was reactivated in 2013, renamed NEOWISE, and given a new mission to identify potentially hazardous near-Earth objects.


Millions of Black Holes Are Hiding in the Milky Way Eating Matter from Interstellar Space

Across the Milky Way, there are millions of undiscovered black holes that are consuming matter from interstellar space, draining our galaxy of dust and gas floating in the voids between stars. Now, a pair of Japanese scientists have announced a plan to hunt down these "lost" black holes.

The idea that there are millions of black holes hiding in the Milky Way is not new. In 2018, NASA-funded research found there could be between 10,000 and 20,000 black holes gathered around the supermassive black hole at the center of the galaxy. Research published February also said there are potentially 100 million "quiet black holes" in the Milky Way.

Tracking these regions in space is difficult, however. The gravitational forces around a black hole are so intense not even light can escape. This means they cannot be detected using traditional methods used to observe other celestial objects.

However, astronomers Daichi Tsuna and Norita Kawanaka, from the University of Tokyo and Kyoto University in Japan, claim to have found a new way of detecting these "isolated black holes" (IBHs).

Their study, which has been posted on the preprint server arxiv.org, suggests observing IBHs through their X-ray emissions. The paper, which is yet to be peer reviewed so has not been assessed by other scientists working in the field, builds on the understanding that IBHs, like all black holes, feed on matter from interstellar space. This produces an accretion disk of matter that surrounds the black hole, which&mdashfor the biggest black holes&mdashproduces X-rays that can be detected by scientists.

But for IBHs, the accretion flow is "unusually weak," meaning it does not produce strong X-ray emissions. However, because of the weak accretion flow, there is a much stronger outflow of material. As LiveScience first reported, Tsuna and Kawanaka focus on the shock produced when this outflow hits the surrounding material. When this happens, electrons are accelerated, producing radio waves that could be detected.

The scientists say the technique is optimistic&mdashdetecting IBHs in this way would require extremely sensitive equipment and would probably could not be used to find the vast majority of these hidden black holes.

Astrophysicist Simon Portegies Zwart, from Leiden University in the Netherlands, who was not involved in the study, told LiveScience that Tsuna and Kawanaka's method of detecting IBHs "would be great" but "the sensitivity may pose a problem."

The authors say the forthcoming Square Kilometer Array (SKA) telescope, which will be based in Australia, may offer capabilities required. "We propose in this paper that IBHs can be one of the promising targets for SKA, and aim to give an estimate on the number of detectable IBHs in the whole Galaxy by the two SKA phases," they say.


Wolf 1061c: Potentially Habitable Super-Earth Spotted 14 Light-Years Away

This artist’s concept depicts a super-Earth. Image credit: NASA / Ames / JPL-Caltech.

Wolf 1061 is a red dwarf star located in the constellation Ophiuchus, only 14 light-years from Earth.

The three exoplanets discovered orbiting this star are between 1.3 and 5.2 times the size of our own, according to the team led by Dr Duncan Wright of the University of New South Wales.

“We have found strong Doppler signals in data for Wolf 1061 that indicate the presence of three planets: a 1.36 Earth minimum-mass planet with an orbital period P = 4.888 d (Wolf 1061b), a 4.25 Earth minimum-mass planet with orbital period P = 17.867 d (Wolf 1061c), and a probable 5.21 Earth minimum-mass planet with orbital period P = 67.274 d (Wolf 1061d),” the team wrote in a paper accepted for publication in the Astrophysical Journal Letters (arXiv.org preprint).

“All of the planets are of sufficiently low mass that they may be rocky in nature.”

The larger outer planet, Wolf 1061d, falls just outside the outer boundary of the habitable zone, while the smaller inner planet, Wolf 1061b, is too close to the star to be habitable.

“The middle planet, Wolf 1061c, sits within the Goldilocks zone where it might be possible for liquid water – and maybe even life – to exist,” said Dr Wright, who is the lead author of the paper.

He and his colleagues from the University of New South Wales made the discovery using data from the HARPS spectrograph on ESO’s 3.6-m telescope in La Silla, Chile.

Wolf 1061 (red star). Image credit: SDSS / Centre de Données astronomiques de Strasbourg / SIMBAD.

Small terrestrial planets are now known to be abundant in our Milky Way Galaxy. However most of them discovered so far are hundreds or thousands of light years away.

An exception is Gliese 667Cc, a potentially habitable exoplanet located 22 light-years from Earth in the constellation Scorpius.

“The close proximity of the planets around Wolf 1061 means there is a good chance these planets may pass across the face of the star,” said co-author Dr Rob Wittenmyer.

“If they do, then it may be possible to study the atmospheres of these planets in future to see whether they would be conducive to life.”


The banality of danger

In listening to these talks I was struck by how mundane the sources of these dangers were when it comes to day-to-day life. Unlike nuclear war or some lone terrorist building a super-virus (threats that Sir Martin Rees eloquently spoke of), when it comes to the climate crisis and an emerging surveillance culture, we are collectively doing it to ourselves through our own innocent individual actions. It's not like some alien threat has arrived and will use a mega-laser to drive the Earth's climate into a new and dangerous state. Nope, it's just us — flying around, using plastic bottles, and keeping our houses toasty in the winter. And it's not like soldiers in black body armor arrive at our doors and force us to install a listening device that tracks our activities. Nope, we willingly set them up on the kitchen counter because they are so dang convenient. These threats to our existence or to our freedoms are things that we are doing just by living our lives in the cultural systems we were born into. And it would take considerable effort to untangle ourselves from these systems.

So, what's next then? Are we simply doomed because we can't collectively figure out how to build and live with something different? I don't know. It's possible that we are doomed. But I did find hope in the talk given by the great (and my favorite) science fiction writer Kim Stanley Robinson. He pointed to how different eras have different "structures of feeling," which is the cognitive and emotional background of an age. Robinson looked at some positive changes that emerged in the wake of the COVID pandemic, including a renewed sense that most of us recognize that we're all in this together. Perhaps, he said, the structure of feeling in our own age is about to change.


Astronomers just found the oldest supermassive black hole yet

Just 670 million years after the Big Bang, a quasar with a monstrous black hole dominated a growing galaxy.

Just 670 million years after the Big Bang, the quasar J0313-1806 was born. It's the most distant black hole ever discovered.

A quasar has been discovered in a dark corner of space more than 13.03 billion light-years away, and it contains a supermassive black hole 1.6 billion times bigger than the sun at its heart.

Dubbed J0313-1806, the quasar, as we see it, is from a time when the universe was just 670 million years old, about 5% of its current age. At such a distance, J0313-1806 becomes the record holder for earliest black hole, dethroning the previous champion , J1342+0928, which was discovered in 2017 and existed when the universe was only 690 million years old.

The discovery, which was announced during the 237th Meeting of the American Astronomical Society on Tuesday, helps shed light on the environment in the ancient universe. But, like any good astrophysics story, it leaves researchers with a number of puzzling questions.

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Quasars are extremely bright objects -- the brightest in the universe. They lie at the center of galaxies, but at their own center lies a supermassive black hole, millions to billions of times more massive than the sun. The intense gravity surrounding the black hole captures gas and dust and potentially even rips apart stars, leaving a trail of debris in a disk that encircles it. The debris whips around at incredible speed and expels extreme amounts of energy, which observers on Earth can see across the electromagnetic spectrum as bright light.

J0313-1806, for instance, shines 1,000 times brighter than the entire Milky Way galaxy.

Astronomers were able to spot the quasar using a handful of ground-based observatories, including the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the world's largest radio telescope, and two observatories on Mauna Kea in Hawaii. The observations enabled researchers to confirm the distance with high precision and examine some of the properties of the supermassive black hole at the quasar's center.

Their calculations put the mass of the black hole at around 1.6 billion times that of the sun. But this poses a problem. Because the black hole can not be older than 670 million years, traditional theories of black hole growth can't account for its size in such a short period of time. Our current understanding of black hole formation involves stars collapsing in on themselves, but the researchers say this would not be able to explain why J0313-1806's black hole is so huge.

"In order for the black hole to have grown to the size we see with J0313-1806, it would have to have started out with a seed black hole of at least 10,000 solar masses," said Xiaohui Fan, an astronomer at the University of Arizona and co-author on an upcoming paper describing the find. "That would only be possible in the direct collapse scenario."

That scenario posits that it's not a star that collapses into a black hole, but instead vast quantities of cold hydrogen gas in a cloud. The direct collapse theory is one of the ways to explain why astronomers find such massive black holes in the early universe, but it's not the only significant find for the team.

Using spectral data, the team also speculates that the supermassive black hole is gobbling up the equivalent of 25 suns every year -- which means it's still growing. "These quasars presumably are still in the process of building their supermassive black holes" said Fan.

The James Webb Space Telescope, which is slated to launch on Oct. 31, could help give scientists another window into the early universe, revealing how these supermassive beasts come to be.

The work has been accepted for publication in Astrophysical Journal Letters.

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Update: Clarification of age of the black hole versus the universe. A previous version of this article stated the black hole is only 670 million years old.