Astronomy

What is the actual visual characteristics of a black hole?

What is the actual visual characteristics of a black hole?


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Is there a safe distance in which a black hole can be observed with the human eye? What is a safe distance?

I have seen many computer simulated and artist renditions, and I am not sure if they depicted the true colors and shape of BH.

Below I have a few of examples of what may a BH may look like rendered.

How light from the accretion disk maybe refracted by gravitational lensing. http://www.physics.utah.edu/~bromley/blackhole/index.html

https://www.bbc.com/news/science-environment-38937141

https://www.nasa.gov/connect/chat/black_hole_chat.html

Should these models be mixed to make a more complete rendition of a BH?


From the Wikipedia black hole article

This is a picture of a real black hole.


This simulation (video link) has been made to show what a black hole might look like seen from different angles.

From APOD :

If the black hole was surrounded by a swirling disk of glowing and accreting gas, then the great gravity of the black hole would deflect light emitted by the disk to make it look very unusual. [… ] Surrounding the central black hole is a thin circular image of the orbiting disk that marks the position of the photon sphere -- inside of which lies the black hole's event horizon. Toward the left, parts of the large main image of the disk appear brighter as they move toward you.


Astronomers capture new polarized view of a black hole

Scientists reveal the first-ever image of a black hole

Former NASA astronaut Mike Massimino explains what can be learned from the groundbreaking discovery.

Scientists from the international Event Horizon Telescope (EHT) collaboration announced Wednesday that they had been able to map the magnetic fields around a black hole using polarized light waves for the first time, releasing a stunning image of the supermassive object at the center of the Messier 87 (M87) galaxy.

The team of more than 300 researchers had produced the first-ever image of a black hole – from 55 million light-years away – in April of 2019.

The researchers published their most recent observations in two separate papers in The Astrophysical Journal, which they say are key to understanding how the M87 galaxy is able to "launch energetic jets from its core."

From data first collected in 2017, the scientists discovered that a significant fraction of the light at the black hole's near-horizon region was polarized.

Light becomes polarized when passing through certain filters or when it is emitted in hot regions of space that are magnetized.

For the first time, EHT scientists have mapped the magnetic fields around a black hole using polarized light waves. With this breakthrough, we have taken a crucial step in solving one of astronomy’s greatest mysteries. (EHT Collaboration)

Astronomers were given a sharper look around the black hole, and the ability to map the magnetic field lines in the surrounding area, by examining how the light around it was polarized.

"These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in the immediate vicinity of the black hole," the group stated in its observational publication. "Here we present the corresponding linear-polarimetric EHT images of the center of M87. We find that only a part of the ring is significantly polarized. The resolved fractional linear polarization has a maximum located in the southwest part of the ring, where it rises to the level of

The group also noted that the polarization position angles are arranged in an almost "azimuthal pattern."

The azimuth is the angle between a fixed point like true North, measured clockwise around the observer's horizon, and a celestial body.

The team wrote that it had performed "quantitative measurements of relevant polarimetric properties of the compact emission" and found "evidence for the temporal evolution of the polarized source structure" over the course of a week.

The data was then carried out by using multiple independent imaging and modeling techniques.

In an accompanying release, the collaboration explained that the energy jets emerging from M87's core extend at least 5,000 light-years from its center.

While most matter near the edge of a black hole falls into it, some of the surrounding particles are blown out in the opposite direction in jets.

Astronomers still don't fully understand this process, nor how matter falls into the black hole, but the new EHT image provides information about the structure of the magnetic fields just outside the black hole.

Only theoretical models with strongly magnetized gas could explain the event, the release says.

"All astronomical objects from the Earth to the Sun to galaxies have magnetic fields. In the case of black holes, these magnetic fields can control how rapidly they consume the matter falling onto them and how they eject some of that matter into narrow beams traveling at close to the speed of light," Geoffrey C. Bower, EHT project scientist at the Academia Sinica Institute of Astronomy and Astrophysics in Hawaii, told Fox News via email on Thursday. "We showed that the fields are indeed strong enough to play an important role in how this black hole eats its lunch."

The EHT collaboration is an evolving network of telescopes across Chile, Spain, Antarctica, Greenland, France, Hawaii, Arizona and Mexico.

In order to observe the M87 galaxy, the collaboration linked eight telescopes to create the EHT: a "virtual Earth-sized telescope" with resolution "equivalent to that needed to measure the length of a credit card on the surface of the Moon."

"This setup allowed the team to directly observe the black hole shadow and the ring of light around it, with the new [polarized-light] image clearly showing that the ring is magnetized," the release said.

"No one has ever made this kind of image before," Bower said. "Remarkably, the data forming this image is the same that was used to make the iconic first image of a black hole released two years ago. We took two years to analyze the data in a new way that allows us to separate the polarizations of light, a process like putting polarized sunglasses on our telescope."


Violent flaring revealed at the heart of a black hole system

An artist's impression of the black hole system MAXI J1820+070, based upon observed characteristics. The black hole is seen to feed off the companion star, drawing the material out into a vast disc of inspiralling matter. As it falls closer to the black hole itself, some of that material is shot out into energetic pencil-beam 'jets' above and below the disc. The light here is intense enough to outshine the Sun a thousand times over. ©John Paice Credit: ©John Paice. Licence type Attribution (CC BY 4.0)

An international team of astronomers, led by the University of Southampton, have used state-of-the-art cameras to create a high frame-rate movie of a growing black hole system at a level of detail never seen before. In the process they uncovered new clues to understanding the immediate surroundings of these enigmatic objects. The scientists publish their work in a new paper in Monthly Notices of the Royal Astronomical Society.

Black holes can feed off a nearby star and create vast accretion discs of material. Here, the effect of the black hole's strong gravity and the material's own magnetic field can cause rapidly changing levels of radiation to be emitted from the system as a whole.

This radiation was detected in visible light by the HiPERCAM instrument on the Gran Telescopio Canarias (La Palma, Canary Islands) and in X-rays by NASA's NICER observatory aboard the International Space Station.

The black hole system studied is named MAXI J1820+070, and was first discovered in early 2018. It is only about 10,000 lightyears away, in our own Milky Way. It has the mass of about 7 Suns, with this collapsed down to a region of space smaller than the City of London.

Investigating these systems is usually very difficult, as their distances make them too faint and too small to see - not even using the Event Horizon Telescope, which recently took a picture of the black hole at the centre of the galaxy M87. The HiPERCAM and NICER instruments however let the researchers record 'movies' of the changing light from the system at over three hundred frames per second, capturing violent 'crackling' and 'flaring' of visible and X-ray light.

John Paice, a graduate student at the University of Southampton and the Inter-University Centre for Astronomy & Astrophysics in India was the lead author of the study presenting these results, and also the artist who created the movie. He explained the work as follows: "The movie was made using real data, but slowed down to 1/10th of actual speed to allow the most rapid flares to be discerned by the human eye. We can see how the material around the black hole is so bright, it's outshining the star that it is consuming, and the fastest flickers last only a few milliseconds – that's the output of a hundred Suns and more being emitted in the blink of an eye."

Researchers also found that dips in X-ray levels are accompanied by a rise in visible light (and vice-versa). And the fastest flashes in visible light were found to emerge a fraction of a second after X-rays. Such patterns indirectly reveal the presence of distinct plasma, extremely hot material where electrons are stripped away from atoms, in structures deep in the embrace of the black hole's gravity, otherwise too small to resolve.

This is not the first time this has been found a split-second difference between X-ray and visual light has been seen in two other systems hosting black holes but it has never been observed at this level of detail. Members of this international team have been at the forefront of this field over the past decade. Dr Poshak Gandhi, also of Southampton, found the same fleeting time signatures in the two previous systems as well.

He commented on the significance of these findings: "The fact that we now see this in three systems strengthens the idea that it is a unifying characteristic of such growing black holes. If true, this must be telling us something fundamental about how plasma flows around black holes operate.

"Our best ideas invoke a deep connection between inspiralling and outflowing bits of the plasma. But these are extreme physical conditions that we cannot replicate in Earth laboratories, and we don't understand how nature manages this. Such data will be crucial for homing in on the correct theory."


So what is a black hole then?

The virtual partical you mention above is sort of like how photovoltaic cells turn photons into voltage. The photon make electron/hole pairs in the silicon, when the pairs are made on oppsite sides of a junction, they're split apart and don't recombine.

#27 Veshtan

#28 HiggsBoson

We have known for a few decades that forward time travel is a consequence of motion. Unfortunately, the mechanism does not provide a way to return to the past. Therefore your car is a time machine as is the case of your morning jog. While we know it works we also know that it take enormous energy to gain sufficient speed to provide useful time acceleration.

I once calculated the energy required to get a ship from a standing start to .86c. I found that the energy required was on the order of the mc^2 energy of the rest mass of the payload.

#29 HiggsBoson

If the core of the BH is actually a point. And the mass hasn't gone away.

Wouldn't that imply that there has to be more that 4 dimensions, And the matter has pushed somewhere else?

Remember the theory does not say anything about matter being pushed away. The theory is a mathematical model that produced a quantitative prediction of the collapse. The theory also does suggest that the collapse takes infinite time when viewed from outside the event horizon.

Since we know that our model breaks down inside of the event horizon discussion about what is in there is call conjecture. Also well meaning people who are attempting to explain the theory use analogies and says things like mass being pushed out of the universe. Such statements are not a part of the theory and can not be used to draw additional physical conclusions to agree with, refute or extend a theory.

#30 Pess

Remember the theory does not say anything about matter being pushed away. The theory is a mathematical model that produced a quantitative prediction of the collapse. The theory also does suggest that the collapse takes infinite time when viewed from outside the event horizon.

Since we know that our model breaks down inside of the event horizon discussion about what is in there is call conjecture. Also well meaning people who are attempting to explain the theory use analogies and says things like mass being pushed out of the universe. Such statements are not a part of the theory and can not be used to draw additional physical conclusions to agree with, refute or extend a theory.

Phrased perfectly by a scientist

For consumption of the masses I would say it more simplistically. The math dealing with the actual singularity describes a condition similar to balancing an incredibly sharpened pencil perfectly on the final atom at its extreme tip.

The math is perfect, and describes a theoretically possible state of the (pencil) singularity. Of course, like stated many places before the math may describe an unbalanced condition (like our pencil analogy) and therefore does not exist in nature.

We do not know enough at the present time to develop the math which could describe other, possibly more stable, states of the singularity that give us the same observed correlations we see today. Carrying the analogy further we cannot, as yet, describe a stable state of the singularity akin to the pencil lying on its side on the desk.

Can I slip through with that one Michael?

Pesse (Scientists really hate describing a line as 4" long when it's really 4.00000000000001") Mist

#31 llanitedave

Pesse (Scientists really hate describing a line as 4" long when it's really 4.00000000000001") Mist

#32 HiggsBoson

#33 HiggsBoson


Pesse (Scientists really hate describing a line as 4" long when it's really 4.00000000000001") Mist

#34 Shadowalker


Pesse (Scientists really hate describing a line as 4" long when it's really 4.00000000000001") Mist


Well Good Grief! An engineer worth his salt would say "close enough is close enough." Engineers aren't looking at black holes. We're looking at other heavenly bodies. Amazing but true.

#35 Pess


Pesse (Scientists really hate describing a line as 4" long when it's really 4.00000000000001") Mist

Un-hunh. When was the last time you saw an engineer buying a round of drinks for everyone because he just computed Pi to a couple million decimal points?

Pesse ( I consider a research mathematician as just a subcategory of scientist.) Mist

#36 HiggsBoson

Without taking the issue too seriously I think a physicist would say

“Consider a line of length L where L is on the order of 4 inches”

In this simple phrase he as both placed the length of the line exactly, length L, and avoided the issues of how precisely L is known.”

A mathematician would tell you the length of the line is 4 inches plus or minus some error epsilon where epsilon is very much less than 4. Then he would then have you to do all of the math dragging around this epsilon and at the end approximate the length of the line in the limit as epsilon goes to zero.

#37 jfosc

I once calculated the energy required to get a ship from a standing start to .86c. I found that the energy required was on the order of the mc^2 energy of the rest mass of the payload.

#38 HiggsBoson

I once calculated the energy required to get a ship from a standing start to .86c. I found that the energy required was on the order of the mc^2 energy of the rest mass of the payload.


I was in collage at the time and just beginning to understand the limitations of Special Relativity. The calculation showed that the speed of light limit is not even the problem. Fuel is the primary limitation in space travel and this limitation is technology independent.

#39 Jeremy Perez

This is an interesting discussion, and a couple folks have touched on something I've often wondered about: just HOW does the event horizon of a black hole grow?

If (from an outside perspective) time slows to a halt just outside the edge of the event horizon, then all inflowing matter that reaches that point would be stuck there--glommed just outside the horizon. I'm not comfortable enough with the math, physics and geometry of that concept to know for sure, but my gut feeling suggests that the event horizon probably grows in response to the accumulated, nearly-frozen matter surrounding it. As a result, even though time has essentially stopped and the matter can no longer proceed inward, the event horizon grows to accommodate and envelope it anyway.

Is that a reasonably correct way of visualizing how the black hole grows even though time dilates to infinity at the event horizon? If so, and if the accretion disc piles the matter up along the 'equator' of the black hole, would that eventually make for a very strangely shaped event horizon?

#40 Pess

This is an interesting discussion, and a couple folks have touched on something I've often wondered about: just HOW does the event horizon of a black hole grow?

All the event horizon is is the point where gravitational attraction from the mass of the black hole is just enough to make the escape velocity equal to the speed of light. Nothing more, nothing less.

Drop more mass into the BH and you increase the gravity of the BH. This enlarges the event horizon.

Just like the escape velocity of the moon is only 1/6 that of earth because the moon has lower mass. If we kept adding mass to the moon the escape velocity would keep increasing until at some point it would be equal to the speed of light and that would be defined as the Event Horizon. The EH would first be next to the surface and, as mass was added, the EH would expand outward.

If (from an outside perspective) time slows to a halt just outside the edge of the event horizon, then all inflowing matter that reaches that point would be stuck there--glommed just outside the horizon. I'm not comfortable enough with the math, physics and geometry of that concept to know for sure, but my gut feeling suggests that the event horizon probably grows in response to the accumulated, nearly-frozen matter surrounding it. As a result, even though time has essentially stopped and the matter can no longer proceed inward, the event horizon grows to accommodate and envelope it anyway.

No. This is wrong. To an outside observer you would never see a buddy heading down in a spaceship reach the EH because the photons coming off him would be retarded by gravity. Since at the event horizon photons, by definition, would not have enough energy to 'escape' you would never observe someone reaching and crossing an EH. They would just appear to get closer and closer and move slower and slower but never seen to reach or cross the EH from YOUR POINT OF OBSERVATION.

Is that a reasonably correct way of visualizing how the black hole grows even though time dilates to infinity at the event horizon? If so, and if the accretion disc piles the matter up along the 'equator' of the black hole, would that eventually make for a very strangely shaped event horizon?

Matter close to BH's eventually drops in and adds to mass increasing its gravity. Over time this moves the EH outward. Massive BH's have huge diameter EH's.

If you took your own spaceship and flew into a BH you would indeed cross the EH with nothing special happening..that is, if you could survive the massive tidal forces.

Pesse (Crossing the Event Horizon is a non-event.) Mist

#41 kraterkid

Black holes are very much like elementary particles. They have mass, spin and charge. There are in effect, two varieties, non-rotating Schwartzchild black holes (mentioned previously by Pess, it looks as if nature would never produce such a beast), and rotating Kerr black holes. We have only a general understanding of the nature of black holes, except at their event horizons and outward. That is directly a consequence of not being able to integrate General Relativity with Quantum Field Theory. To comprehend the nature of the singularity at the core of a black hole, our Grand Unification Theory must deal with the most severely warped spacetime and the most energetic forms of matter and energy. This is, in fact, the major unsolved problem in Physics today. Eventually if we are lucky enough and resourceful enough, we may finally solve the equations that will give us a much more sophisticated comprehension of the singularity itself. Until then, it will remain enignimatic.

I was in collage at the time and just beginning to understand the limitations of Special Relativity. The calculation showed that the speed of light limit is not even the problem. Fuel is the primary limitation in space travel and this limitation is technology independent.

#42 Pess

Michael (Higgs Boson), from my understanding of SR, there is no amount of energy that can accelerate a spacecraft to or beyond the velocity of light. This is a consequence of the extra mass that a body in motion attains as it is accelerated. According to Einstein, this extra mass resists acceleration and we must keep firing our engines to overcome this extra mass. But this new acceleration adds more extra mass, and again the need for more energy in order to accelerate. Therefore our velocity approaches, but never equals or exceeds the velocity of light. We may be able to play games with spacetime in the future, as a result of our understanding of Quantum Gravity, such as opening a hole in spacetime with exotic matter and moving through it to end up in a another part of the universe or by severely warping space around us as we accelerate through normal space to find ourselves many light years away, but the "C" speed limit still applies in our physical universe.

I hate to be nit-picky but Einstein only said that we can not go AT the speed of light. He said nothing about traveling faster than the speed of light.

And yes, I know that mass approaches infinity as speed approaches that of light making it a real challenge for even a Shelby Mustang to approach the limit.

We just need a way around the problem of actually going at the speed of light.

I just ordered an inertial damper (effectively a mass neutralizer) from Star Fleet Marine Depot (The Heisenberg uncertainty compensator was back ordered). We'll just dial that inertia all the way down to zero and Whooooooooooooooooosh we are going the speed of light! Hmmm, better pack some extra Twinkies. Still four+ years to the nearest star.

Pesse (If someone will please lift a corner of the fabric of space so i can just crawl under?) Mist

#43 kraterkid

#44 jfosc

I hate to be nit-picky but Einstein only said that we can not go AT the speed of light. He said nothing about traveling faster than the speed of light.

Pess, my recollection is that Einstein described the speed of light as the "cosmological speed limit". It's well known he didn't believe that "God played dice" in terms of quantum uncertainty in quantum field theory. He couldn't accept instantaneous action - so he could not accept that two particles significantly separated spatially could interact faster than light.


I don't have any resources to cite from Einstein directly, but if anyone does with respect to "faster than light" speed please feel free to contribute.

#45 Qkslvr

Rich, Electrons tunnel through insulators all the time, And tachyon's are theoretical FTL particles.

I personally still have FTL travel in the "Not proven impossible yet" category.

Plus we've found clumps of jupiter sized matter at 99.99.. to 19 places % of the Speed of Light being spit out of as it so happens a rotating black hole.

Which BTW has to beat the energy we'll be able to muster up in our accellerators for a while anyways.

#46 Pess

Pess, I believe Einstein said that matter cannot be accelerated to the speed of light. Whether "at" or "beyond" is irrelevant, if you cannot get there.

The fine point I made is not 'irrelevant'.

We must be careful about broad claims relative to relativity. Einstein clearly does not say we can't accelerate to the speed of light, only that we can't reach that one specific "speed". We can accelerate toward 'it' all day long as long as the battery pack holds out.

Mass has this weird characteristic called 'inertia'. We have absolutely no idea what causes it. (and I don't want to hear about the 'Higgs field, it's lame)

If we can discover what it is about matter and/or spacetime that bestows inertia on matter then the universe is ours.

On a broader note, mass has certain characteristics that not only identify it as we commonly perceive it, but also notify the universe as to its position (and mass and other things).

This is perhaps too heavy a concept for most to wrap their minds around but some element(s) we are not yet appreciative of reside in matter to define to the space/time 'fabric' where it should reside. If we can access this 'positional information' than perhaps flipping stars into say, the profile of Brittany Spears, might not be so far-fetched.

But again, I digress, my point was that Einstein says nothing about speeds in excess of light speed and indeed, the same equations that prohibit reaching light speed also easily can describe the proposed existence of 'tachyons' that can approach light speed but never quite slow down to it. Tachyons can even have 'mass'!

OK, now you are rolling your eyes and saying "Pess-ee, old boy, go back to the marble pile and restock!" Particles that have mass can never reach light speed so they can never go faster! End of argument! get help!"

Consider though. Theories today pretty much support the concept of pairs of 'Virtual Particles' that appear and disappear in the fabric of space. Indeed, this is the source of Hawking radiation from black holes as Virtual pairs appear next to an Event Horizon, and the BH snatches one of the pair away leaving the other to zip off into space as a 'Real particle' (after stealing a bit of energy from the BH itself to make the change). Hence BH evaporation.

Now these Virtual pairs can be anything. So suppose they are 'Virtual Tachyons". They already travel FTL when they come into existence, so there is no need to accelerate them. Now if a BH EH snatches one, the other pops into 'Real' existence and streaks off. VIOLA! Instant FTL particle with mass!

Now I am not saying tachyons exist for there is scant proof at present, but Einsteins math describe the situation I just outlined as just as likely as anything else. Math is fun!

Pesse (But math describes a lot of possibilities that can't be found in the real world..or can they? Tachyions ) Mist


By Kate Blackwood |

One of the key goals of gravitational wave astronomy is to understand and characterize binary black hole spins, according to Vijay Varma, a Klarman Postdoctoral Fellow in physics in the College of Arts and Sciences.

By measuring the masses and spin rates of binary black hole systems in which two of the super-compact astronomical objects orbit each other, using gravitational waves emitted as the objects merge, researchers can gain insight into larger questions in astrophysics, including general relativity and the lifespan of stars.

In “New spin on LIGO-Virgo binary black holes,” published in Physical Review Letters on April 29, Varma and collaborators proposed a novel way of studying binary black holes by identifying each of their individual component black holes by their spins – rather than their masses – which leads to an improved measurement of the spins. The researchers applied the new method to analyze binary black hole data gathered by the LIGO and Virgo gravitational wave detectors.

“Rather than attempting to identify the spin of the heaviest and lightest of the two objects, as is usually done, we infer the properties of the objects with the highest and lowest spin,” the researchers wrote. This refocus on the black holes’ spins, rather than their masses, gives a new importance to spin measurements in binaries in which the masses of the two black holes are nearly equal – “which appear to be the majority,” they wrote.

Their finding potentially changes the way scientists study black holes, which provide insight into general relativity and our knowledge of the evolution of stars, among other large questions.

“We realized that for systems where the two black holes in the binary have equal masses or close to equal masses, it’s hard to measure the spin,” Biscoveanu said. The team reframed the question to look directly at the spin of the black hole with the highest spin and the black hole with the lowest spin.

Varma and collaborators (lead author Sylvia Biscoveanu, Maximiliano Isi and Salvatore Vitale, all from the Massachusetts Institute of Technology) were inspired to pursue this line of research while studying data from GW190521, a binary black hole system detected by LIGO, a very sensitive instrument which detects gravitational waves from astronomical objects, including black holes. This system is particularly interesting, the researchers said, because it is the most massive detected to date, and it also demonstrates evidence for a unique spin signature that hadn’t previously been observed.

“We are especially interested in systems that have spins because they carry a lot of astrophysical information that can tell us how these binaries were formed in the first place,” said Varma, an expert on developing ‘surrogate models', which allow researchers to determine characteristics of black holes based on supercomputer simulations.

Black holes are incredibly heavy and dense, Varma said, typically 10 to 30 times more massive than the sun, sometimes heavier, but packed into a space about the size of Hawaii.

Biscoveanu compared measuring the mass and the spin of a binary black hole system to measuring the temperature and the sweetness of two juices. “You would measure the temperature of the coldest juice that you’re tasting and the sweetness of the sweetest juice,” she said. “You wouldn’t try to measure the sweetness of the coldest juice because that’s a convoluted question, especially if both of them are the same temperature.”

The researchers said that inquiring about the fastest spinning black hole helps researchers learn more about individual binary black hole systems, or a whole population of binary black holes, such as those observed via gravitational waves by the LIGO-Virgo collaboration.

“That has implications for how stars evolve and form black holes,” Varma said. “We can go back to the earlier stages of the evolution and try to understand the secrets of black hole astrophysics.”

The research was funded by the Klarman Postdoctoral Fellowship in A&S, the Sherman Fairchild Foundation,the National Science Foundation, the Paul and Daisy Soros Fellowship and the NASA Hubble Fellowship.

Kate Blackwood is a writer for the College of Arts and Sciences.


The Tell-Tale Radiation Signature

Those radiation signatures are important clues to the very existence of a black hole, which does not give off any radiation of its own. All the radiation we see is coming from the objects and material around it. So, astronomers look for the telltale radiation signatures of matter being gobbled up by black holes: x-rays or radio emissions, since the events that emit them are very energetic.

After studying black holes in distant galaxies, astronomers noticed that some galaxies suddenly brighten up at their cores and then slowly dim down. The characteristics of the light given off and the dim-down time came to be known as signatures of black hole accretion disks eating nearby stars and gas clouds, giving off radiation.


Astronomers Capture the First Image of a Black Hole

The Event Horizon Telescope (EHT), a planet-scale array of eight ground-based radio telescopes forged through international collaboration, was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers reveal that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.

This breakthrough was announced today in a series of six papers published in a special issue of The Astrophysical Journal Letters. The image reveals the black hole at the center of Messier 87 1 , a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5-billion times that of the Sun 2 .

The EHT links telescopes around the globe to form an Earth-sized virtual telescope with unprecedented sensitivity and resolution 3 . The EHT is the result of years of international collaboration, and offers scientists a new way to study the most extreme objects in the Universe predicted by Einstein’s general relativity during the centennial year of the historic experiment that first confirmed the theory 4 .

“We are giving humanity its first view of a black hole — a one-way door out of our Universe,” said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian. “This is a landmark in astronomy, an unprecedented scientific feat accomplished by a team of more than 200 researchers.

Black holes are extraordinary cosmic objects with enormous masses but extremely compact sizes. The presence of these objects affects their environment in extreme ways, warping spacetime and super-heating any surrounding material.

“If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow — something predicted by Einstein’s general relativity that we’ve never seen before,” explained chair of the EHT Science Council Heino Falcke of Radboud University, the Netherlands. “This shadow, caused by the gravitational bending and capture of light by the event horizon, reveals a lot about the nature of these fascinating objects and allowed us to measure the enormous mass of M87’s black hole.”

Multiple calibration and imaging methods have revealed a ring-like structure with a dark central region — the black hole’s shadow — that persisted over multiple independent EHT observations.

Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well,” remarks Paul T.P. Ho, EHT Board member and Director of the East Asian Observatory 5 . “This makes us confident about the interpretation of our observations, including our estimation of the black hole’s mass.”

Creating the EHT was a formidable challenge which required upgrading and connecting a worldwide network of eight pre-existing telescopes deployed at a variety of challenging high-altitude sites. These locations included volcanoes in Hawai and Mexico, mountains in Arizona and the Spanish Sierra Nevada, the Chilean Atacama Desert, and Antarctica.

The EHT observations use a technique called very-long-baseline interferometry (VLBI) which synchronizes telescope facilities around the world and exploits the rotation of our planet to form one huge, Earth-size telescope observing at a wavelength of 1.3mm. VLBI allows the EHT to achieve an angular resolution of 20 micro-arcseconds — enough to read a newspaper in New York from a sidewalk café in Paris 6 .

The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope 7 . Petabytes of raw data from the telescopes were combined by highly specialised supercomputers hosted by the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory.

The construction of the EHT and the observations announced today represent the culmination of decades of observational, technical, and theoretical work. This example of global teamwork required close collaboration by researchers from around the world. Thirteen partner institutions worked together to create the EHT, using both pre-existing infrastructure and support from a variety of agencies. Key funding was provided by the US National Science Foundation (NSF), the EU’s European Research Council (ERC), and funding agencies in East Asia.

ALMA is the largest millimeter wave telescope in the world and so was critical in the collaboration,” said ALMA Director Sean Dougherty “It really helped to ensure high-quality calibration of the data to each of the other telescopes in the array, resulting in the fantastic images from the EHT.”

“We have achieved something presumed to be impossible just a generation ago,” concluded Doeleman. “Breakthroughs in technology and the completion of new radio telescopes over the past decade enabled our team to assemble this new instrument — designed to see the unseeable.”

Additional Information

This research was presented in a series of six papers published today in a special issue of The Astrophysical Journal Letters.

The EHT collaboration involves more than 200 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved are ALMA, APEX, the IRAM 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope Alfonso Serrano (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT).

The EHT Collaboration consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Links

  • Paper I: The Shadow of the Supermassive Black Hole
  • Paper II: Array and Instrumentation
  • Paper III: Data processing and Calibration
  • Paper IV: Imaging the Central Supermassive Black Hole
  • Paper V: Physical Origin of the Asymmetric Ring
  • Paper VI: The Shadow and Mass of the Central Black Hole

Images and videos

The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of the supermassive black hole in the center of Messier 87 and its shadow.
The shadow of a black hole seen here is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across. While this may sound large, this ring is only about 40 microarcseconds across — equivalent to measuring the length of a credit card on the surface of the Moon.
Although the telescopes making up the EHT are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialized supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration. Credit: EHT Collaboration

Messier 87 (M87) is an enormous elliptical galaxy located about 55 million light years from Earth, visible in the constellation Virgo. It was discovered by Charles Messier in 1781, but not identified as a galaxy until 20th Century. At double the mass of our own galaxy, the Milky Way, and containing as many as ten times more stars, it is amongst the largest galaxies in the local universe. Besides its raw size, M87 has some very unique characteristics. For example, it contains an unusually high number of globular clusters: while our Milky Way contains under 200, M87 has about 12,000, which some scientists theorize it collected from its smaller neighbors.
Just as with all other large galaxies, M87 has a supermassive black hole at its center. The mass of the black hole at the center of a galaxy is related to the mass of the galaxy overall, so it shouldn’t be surprising that M87’s black hole is one of the most massive known. The black hole also may explain one of the galaxy’s most energetic features: a relativistic jet of matter being ejected at nearly the speed of light.
The black hole was the object of paradigm-shifting observations by the Event Horizon Telescope. The EHT chose the object as the target of its observations for two reasons. While the EHT’s resolution is incredible, even it has its limits. As more massive black holes are also larger in diameter, M87’s central black hole presented an unusually large target—meaning that it could be imaged more easily than smaller black holes closer by. The other reason for choosing it, however, was decidedly more Earthly. M87 appears fairly close to the celestial equator when viewed from our planet, making it visible in most of the Northern and Southern Hemispheres. This maximized the number of telescopes in the EHT that could observe it, increasing the resolution of the final image.
This image was captured by FORS2 on ESO’s Very Large Telescope as part of the Cosmic Gems program, an outreach initiative that uses ESO telescopes to produce images of interesting, intriguing or visually attractive objects for the purposes of education and public outreach. The program makes use of telescope time that cannot be used for science observations, and produces breathtaking images of some of the most striking objects in the night sky. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through the ESO Science Archive. Credit: ESO

Comparison of the image of M87 taken by EHT with and without Chilean Telescopes (ALMA-APEX). Credit: EHT Collaboration

This artist’s impression depicts the black hole at the heart of the enormous elliptical galaxy Messier 87 (M87). This black hole was chosen as the object of paradigm-shifting observations by the Event Horizon Telescope. The superheated material surrounding the black hole is shown, as is the relativistic jet launched by M87’s black hole. Credit: ESO/M. Kornmesser

In anticipation of the first image of a black hole, Jordy Davelaar and colleagues built a virtual reality simulation of one of these fascinating astrophysical objects. Their simulation shows a black hole surrounded by luminous matter. This matter disappears into the black hole in a vortex-like way, and the extreme conditions cause it to become a glowing plasma. The light emitted is then deflected and deformed by the powerful gravity of the black hole. Credit: Jordy Davelaar et al./Radboud University/BlackHoleCam

In anticipation of the first image of a black hole, Jordy Davelaar and colleagues built a virtual reality simulation of one of these fascinating astrophysical objects. Their simulation shows a black hole surrounded by luminous matter. This matter disappears into the black hole in a vortex-like way, and the extreme conditions cause it to become a glowing plasma. The light emitted is then deflected and deformed by the powerful gravity of the black hole. Credit: Jordy Davelaar et al./Radboud University/BlackHoleCam

This artist’s impression depicts a rapidly spinning supermassive black hole surrounded by an accretion disc. This thin disc of rotating material consists of the leftovers of a Sun-like star which was ripped apart by the tidal forces of the black hole. The black hole is labelled, showing the anatomy of this fascinating object. Credit: ESO

Simulated image of an accreting black hole. The event horizon is in the middle of the image, and the shadow can be seen with a rotating accretion disk surrounding it. Credit: Bronzwaer/Davelaar/Moscibrodzka/Falcke/Radboud University

This image shows the locations of some of the telescopes making up the EHT, as well as the long baselines between the telescopes. Credit: ESO/ L. Calçada

This chart shows the position of giant galaxy Messier 87 in the constellation of Virgo (The Virgin). The map shows most of the stars visible to the unaided eye under good conditions. Credit: ESO, IAU and Sky & Telescope

This artist’s impression depicts the surroundings of a black hole, showing an accretion disc of superheated plasma and a relativistic jet. Credit: Nicolle R. Fuller/NSF

This artist’s impression depicts the paths of photons in the vicinity of a black hole. The gravitational bending and capture of light by the event horizon is the cause of the shadow captured by the Event Horizon Telescope. Credit: Nicolle R. Fuller/NSF

This poster from the NRAO explains some of the key concepts in interferometry, the breakthrough that made the Event Horizon Telescope observations of M87’s black hole possible. Credit: NRAO/AUI/NSF S. Dagnello

This diagram shows the location of the telescopes used in the 2017 EHT observations of M87. Credit: NRAO

In the Shadow of a Black Hole. The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow. This 17-minute film explores the efforts that led to this historic image, from the science of Einstein and Schwarzschild to the struggles and successes of the EHT collaboration. Credit:ESO

Zooming in to the Heart of Messier 87. The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow. This zoom video starts with a view of ALMA and zooms in on the heart of M87, showing successively more detailed observations and culminating in the first direct visual evidence of a supermassive black hole’s shadow. Credit: ESO/L. Calçada, Digitized Sky Survey 2, ESA/Hubble, RadioAstron, De Gasperin et al., Kim et al., EHT Collaboration. Music: niklasfalcke

Simulation of a Supermassive Black Hole. In anticipation of the first image of a black hole, Jordy Davelaar and colleagues built a virtual reality simulation of one of these fascinating astrophysical objects. Their simulation shows a black hole surrounded by luminous matter. This matter disappears into the black hole in a vortex-like way, and the extreme conditions cause it to become a glowing plasma. The light emitted is then deflected and deformed by the powerful gravity of the black hole. Credit: Jordy Davelaar et al./Radboud University/BlackHoleCam

Artist’s impression of the Black Hole at the heart of M87. This artist’s impression depicts the black hole at the heart of the enormous elliptical galaxy M87. This black hole was chosen as the object of paradigm-shifting observations by the Event Horizon Telescope. The superheated material surrounding the black hole is shown, as is the relativistic jet launched by M87’s black hole. Credit: ESO/M. Kornmesser

The EHT, a Planet-Scale Array This animation shows the locations of some of the telescopes making up the EHT, as well as the long baselines between the telescopes. Credit:ESO/ L. Calçada

  1. The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across. ↩
  2. Supermassive black holes are relatively tiny astronomical objects — which has made them impossible to directly observe until now. As the size of a black hole’s event horizon is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth — making it a perfect target for the EHT. ↩
  3. Although the telescopes are not physically connected, they are able to synchronize their recorded data with atomic clocks — hydrogen masers — which precisely time their observations. These observations were collected at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced enormous amounts of data – roughly 350 terabytes per day – which was stored on high-performance helium-filled hard drives. These data were flown to highly specialised supercomputers — known as correlators — at the Max Planck Institute for Radio Astronomy and MIT Haystack Observatory to be combined. They were then painstakingly converted into an image using novel computational tools developed by the collaboration. ↩
  4. 100 years ago, two expeditions set out for Principe Island off the coast of Africa and Sobral in Brazil to observe the 1919 solar eclipse, with the goal of testing general relativity by seeing if starlight would be bent around the limb of the sun, as predicted by Einstein. In an echo of those observations, the EHT has sent team members to some of the world’s highest and most isolated radio facilities to once again test our understanding of gravity. ↩
  5. The East Asian Observatory (EAO) partner on the EHT project represents the participation of many regions in Asia, including China, Japan, Korea, Taiwan, Vietnam, Thailand, Malaysia, India and Indonesia. ↩
  6. Future EHT observations will see substantially increased sensitivity with the participation of the IRAM NOEMA Observatory, the Greenland Telescope and the Kitt Peak Telescope. ↩
  7. ALMA is a partnership of the European Southern Observatory (ESO Europe, representing its member states), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences(NINS) of Japan, together with the National Research Council (Canada), the Ministry of Science and Technology (MOST Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA Taiwan), and Korea Astronomy and Space Science Institute (KASI Republic of Korea), in cooperation with the Republic of Chile. APEX is operated by ESO, the 30-meter telescope is operated by IRAM(the IRAM Partner Organizations are MPG (Germany), CNRS (France) and IGN (Spain)), the James Clerk Maxwell Telescopeis operated by the EAO, the Large Millimeter Telescope Alfonso Serrano is operated by INAOE and UMass, theSubmillimeter Array is operated by SAO and ASIAA and the Submillimeter Telescope is operated by the Arizona Radio Observatory (ARO). The South Pole Telescope is operated by the University of Chicago with specialized EHT instrumentation provided by the University of Arizona.↩

Black holes

They encounter a planet near a black hole, and decide to go around it to avoid the “time shift zone” - they talk about time shift as if it has a distinct boundary but it just doesn’t work like that - it’s gradual, progressive, and is the same in all directions. Also, if there’s such a strong gravitational field, then the planet itself would be destroyed by the difference in gravity between its opposite sides. Finding a stable planet within such a strong gravitational field is a stretch of the imagination. It just wouldn’t happen.

The visual presentation of the black hole – a big disc of luminous matter rotating around it being eaten up by the gravitational pull - is certainly plausible. But if you were to find yourself in this region, you are as likely to die from the radiation from the disc, which is very hot and emitting gamma rays, as much as from the gravitational pull. When you are close to a black hole, the gravity at your feet will be much stronger than the gravty at your head, so you get spaghettified, stretched out, like a piece of spaghetti, into a filament of matter. We see no evidence of that happening.


New telescopes to help astronomers acquire sharper black hole images

May 6 (UPI) -- Earlier this year, scientists captured the first up-close image of a black hole. Now, researchers are working on plans to produce even sharper images of the cosmic phenomena.

Scientists published their plans for acquiring better black hole images this week in the journal Astronomy and Astrophysics. The plans involve the deployment of two or three coordinated orbital radio telescopes.

To showcase the power of their planned constellation of observatories, dubbed the Event Horizon Imager, researchers developed a model to simulate the telescopes' image-making abilities.

"There are lots of advantages to using satellites instead of permanent radio telescopes on Earth, as with the Event Horizon Telescope," Freek Roelofs, a PhD candidate at Radboud University in the Netherlands, said in a news release. "In space, you can make observations at higher radio frequencies, because the frequencies from Earth are filtered out by the atmosphere."

"The distances between the telescopes in space are also larger," Roelofs said. "This allows us to take a big step forward. We would be able to take images with a resolution more than five times what is possible with the EHT."

EHT was used to produce the first-of-their-kind black hole images published earlier this year. While groundbreaking, the images produced by EHT aren't sharp enough to test Einstein's Theory of General Relativity.

According to the newly published paper, a space-based constellation of black-hole-hunting radio telescopes would be able to measure difference in the behavior of real black holes and the characteristics predicted by Einstein's theory.

To make the astronomers' plans a reality, engineers will have to overcome some technical challenges.

"The concept demands that you must be able to ascertain the position and speed of the satellites very accurately," said Volodymyr Kudriashov, researcher at the Radboud Radio Lab. "But we really believe that the project is feasible."

Initially, scientists expect the EHI telescopes to function independently of the EHT observatories, but the two systems could be eventually combined.

"Using a hybrid like this could provide the possibility of creating moving images of a black hole, and you might be able to observe even more and also weaker sources," said Heino Falcke, a professor of radio astronomy at Radboud.


10 Interesting Facts About Black Holes

Of all the strange objects that exist in the Universe, black holes are without doubt the strangest. In 1971, Cygnus X-1, the first physical black hole ever discovered, may have moved black holes away from being thought of as purely theoretical phenomena, but nevertheless they still continue to maintain their mystery and hold an almost science fiction status.

For instance, these super dense objects are so powerful that the singularity at the center of a black hole is a one-dimensional point which can’t adequately be described by the laws of physics as we know them. Also, by keeping a safe distance from a black hole’s event horizon, a spaceship could travel centuries into the future relative to Earth, although just a few hour would seem to have passed for those people onboard the spaceship.

With that said, let’s dive right in a explore 10 interesting and fun facts about these fascinating objects.

1: How are black holes formed?

A massive star collapsing in upon itself – A black hole is formed when a large star starts running out of fuel and begins to collapse under its own gravity. Such a star may become a white dwarf or a neutron star, but if the star is sufficiently massive then it may continue shrinking eventually to the size of a tiny atom, known as a gravitational singularity. A black hole refers to the region in space in which the singularity’s gravitational force is so strong that not even light can escape its pull.

2: What’s inside a black hole?

Singularity always remains in your future – The singularity at the core of a black hole may shrink to a size smaller than an atom, and eventually become an infinitely small point in space containing infinite mass. Here the gravitational force is so strong that the spacetime surrounding the singularity is bent to infinite curvature, and scientists are left searching for a good quantum theory of gravity to explain what is truly going on inside these incredibly dense objects. As American theoretical physicist Kip Thorne states in his description of a singularity, it is a “point where all laws of physics break down”.

3: How do black holes affect space-time?

Black holes distort space-time and slow time – The mass of a black hole is so dense and the gravity of its singularity so strong that, in accordance with Einstein’s theory of general relativity, it actually distorts the space-time around it and not even light can escape. The boundary beyond which light cannot escape the black hole’s gravity well is known as the event horizon, while its radius is called the Schwarzschild radius (see picture for details). Once particles and light-rays go past the event horizon their light cones “tip over” and point to the singularity, which now represents all future-directed paths with no escape possible.

4: Why do objects appear to “freeze” near a black hole?

Objects appear to slow down near a black hole – To an outside observer with a telescope , an object passing the event horizon will appear to slow down then “freeze” in time without ever seeming to pass through the event horizon. This is because the light takes longer to escape the black hole’s gravitational pull and light signals won’t reach the viewer for an infinitely long time. As time elapses, the light subsequently becomes red shifted and dimmer as its wavelength becomes longer, eventually disappearing from the sight of the observer as it becomes infrared radiation, then radio waves.

5: Can you survive inside a black hole?

A person falling into a black hole would be spagettified – If a person was able to survive long enough to describe falling into a black hole, he would at first experience weightless as he goes into free fall, but then feel intense “tidal” gravitational forces as he got closer to the center of the black hole. In other words, if his feet were closer to the center than his head, then they would feel a stronger pull until he eventually is stretched and then ripped apart. As he falls in he may observe distorted images as the light bends around him and he will also still be able to see beyond the black hole as light continues to reach him from the outside.

6: What is the gravitational pull of a black hole?

Gravitational pull same as other objects of same mass – It is important to realize that a black hole’s gravitational field is the same as that of any other object in space of the same mass. In other words, it won’t “suck” objects in any more than any other normal star, with things being more likely to just fall into them if they got too close to the event horizon. If our Sun was replaced with a black hole of equal mass, for example, the Earth would continue experiencing the same gravitational force as before. Only when objects get too close to the black hole would the stronger gravitational force become apparent.

7: Is a wormhole and a black hole the same?

Wormholes appear similar to black holes – A traversable wormhole, known alternatively as a Lorentzian wormhole, Schwarzschild wormhole or Einstein-Rosen bridge, is a theoretical opening in space-time allowing a “shortcut” through intervening space to another location in the Universe. However, from the outside wormholes may exhibit many of the characteristics usually associated with a black hole and be virtually impossible to tell apart.

8: Who discovered black holes?

John Mitchell developed theory of black holes in 1783 – John Michell (1783) and Pierre-Simon Laplace (1796) were the first people to propose the concept of “dark stars” or object which, if compressed into a small enough radius, would have an escape velocity which exceeded even the speed of light. Later, the term “frozen star” was used to describe the last phase of a star’s gravitational collapse, when light unable to escape from its surface would make the star appear frozen in time to an observer. In the 20th century, John Wheeler eventually coined the phrase “black hole” as the object would absorbs all the light that hits it while reflecting nothing back.

9: Can a black hole die?

Black holes eventually evaporate over time – Physicists now believe that black holes actually radiate small numbers of mainly photon particles and so can lose mass, shrink then ultimately vanish over time. This unverified evaporation process is known as “Hawking Radiation”, after Professor Stephen Hawking who theorized its existence in 1974. However, it is a staggeringly slow process and only the smallest black holes would have had time to evaporate significantly during the 14 billion years the Universe has existed.

10: What is the nearest black hole to Earth?

Closest black hole star just 1,011 light-years away – It is now thought that most galaxies are held together by supermassive black holes at their centers , which cluster hundreds of solar systems around them. In fact, 25,640 light years away at the center of our own Milky Way galaxy is a black hole called Sagittarius A or Sgr A that has 30 million times the mass of our own sun. This is not the nearest black hole to Earth, though. That honor belongs to a recently discovered black hole located in the star system HR 6819.


A Colorful Image of a Black Hole

Editor’s note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites the original can be viewed at astrobites.org.

Title: Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
Authors: The Event Horizon Telescope Multi-wavelength Science Working Group
First Author’s Institution: N/A
Status: Published in ApJL

M87 is a galaxy of extremes — it is one of the brightest radio sources in the entire sky, one of the nearest galaxies that has a relativistic jet emitted from its nucleus, and one of our nearest extragalactic neighbors (a measly 53 million light-years away, in the Virgo Cluster). Also, in 2019, M87 made the news for hosting the subject of the first ever image of a black hole “shadow” (check out the Astrobites coverage of that historic event here).

The first detailed image of a black hole, M87, taken with the Event Horizon Telescope. [Adapted from EHT collaboration et al 2019]

Reducing these uncertainties is imperative if we want to have a better understanding of M87, but radio observations alone cannot accomplish this. Luckily, input from other wavelengths can go a long way in complementing the radio observations. For example, previous multi-wavelength studies of M87 guided our understanding that M87 must have a non-zero spin.

A difficulty, however, is coordinating these observations. The emission from supermassive black holes (SMBHs) of M87’s size — and the jets that they launch — is known to fluctuate on timescales of a few weeks. Thus, to get a complete snapshot of a SMBH, you want to look at it in many wavelengths at roughly the same time. This is exactly what the authors of today’s paper accomplished.

This coordination of telescopes was no small feat. In total, 17 telescopes across as many orders of magnitude in frequency (from 1 GHz to 10 18 GHz) came together to image the nucleus and jet of M87 in 2017. The schedule of the different observations from each telescope is displayed in Figure 1.

Figure 1: Schedule of when each telescope was observing M87 in 2017. The telescopes are ordered by frequency, with red being the lower frequencies (radio). Fermi-LAT normally operates in a survey mode, which is why there is data from every day. [The EHT MWL Science Working Group et al. 2021]

Figure 2: Compilation of the near-simultaneous observations of M87. Note the different angular scales, and how some of the radio observations on the left are able to differentiate features in the jet, whereas gamma-ray observations (right) cannot discriminate between these features. [EHT Collaboration NASA/Swift NASA/Fermi Caltech-NuSTAR CXC CfA-VERITAS MAGIC HESS]

For example, if there are electrons in the jet, then they will emit synchrotron radiation as they spiral around magnetic field lines. This causes a bump in the SED at radio frequencies. Some of the synchrotron radiation can then actually interact with the same electrons, and get scattered up to very high energies, which can cause another bump in the SED at very high energies. Different predictions for, say, the distribution of electrons or the magnetic field strength will change the locations and magnitudes of these “bumps,” and so we can use the SED to infer characteristics about the composition of the jet. The SED from M87 is shown in Figure 3.

Figure 3: Broadband spectral energy distribution (SED) of M87 from 2017. The SED represents the amount of energy arriving at Earth at each of these frequencies. Different features in the SED can reveal valuable information about the environments producing the emission. [The EHT MWL Science Working Group et al. 2021]

From a deep look at M87’s SED, the authors come to the conclusion that a simple model of the emission — one that treats all of the emission as coming from the same location in the jet — cannot explain the entire SED. This lends evidence to the hypothesis that M87’s jet must have a more complex structure, and that the very high-energy gamma rays might be originating from a different region of the jet than the emission at lower frequencies.

Not only are the scientific takeaways from this work extremely informative, but it represents a massive success in uniting some of the most advanced telescopes in the world to create one of the most detailed snapshots of an AGN to date. These observations will serve as a cornerstone for future observations of M87, which will revolutionize our understanding of black holes and relativistic jets.

Original astrobite edited by Viraj Karambelkar.

About the author, Alex Pizzuto:

Alex is a PhD candidate at the Wisconsin IceCube Particle Astrophysics Center at the University of Wisconsin-Madison. His work focuses on developing methods to locate the universe’s most extreme cosmic accelerators by searching for the neutrinos that come from them. Alex is also passionate about local science outreach events in Madison, and enjoys hiking, cooking, and playing music when he is not debugging his code.



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