Observing the invisible: The long journey to the first image of a black hole

Observing the invisible: the long journey to the first image of a black hole
The first direct visual evidence of the supermassive black hole in the centre of galaxy Messier 87 and its shadow. Credit: EHT Collaboration

The first picture of a supermassive black hole at the centre of a galaxy shows how we have, in a sense, observed the invisible.

The ghostly image is a radio intensity map of the glowing plasma behind, and therefore silhouetting, the black hole's "event horizon"—the spherical cloak of invisibility around a black hole from which not even light can escape.

The radio "photograph" was obtained by an involving more than 200 scientists and engineers who linked some of the world's most capable radio telescopes to effectively see the in the galaxy known as M87.

So how on Earth did we get to this point?

From 'dark stars'

It was the English astronomer John Michell who in 1783 first formulated the idea of "dark stars" so incredibly dense that their gravity would be impossible to run from—even if you happened to be a photon able to move at the speed of light.

Things have come a long way since that pioneering insight.

In January this year, astronomers published an image of the emission coming from the radio source known as Sagittarius A*, the region immediately surrounding the supermassive black hole at the centre of our galaxy.

Impressively, that image had detail on scales down to just nine times the size of the black hole's event horizon.

Now, the Event Horizon Telescope (EHT) has succeeded in resolving the event horizon around the supermassive black hole in M87, a relatively nearby galaxy from which light takes 55 million to reach us, due to its distance.

Astronomical figures

Astronomical objects come with astronomical figures, and this target is no exception.

M87's black hole has a mass that is 6.5 billion times that of our Sun, which itself is one-third of a million times the mass of the Earth. Its event horizon has a radius of roughly 20 billion kilometres, more than three times the distance Pluto is from our Sun.

It is, however, far away, and the incredible engineering feat required to see such a target is akin to trying to observe an object 1mm in size from a distance of 13,000 km.

This Nobel Prize-worthy result is, of course, no accidental discovery, but a measurement built on generations of insight and breakthrough.

Predictions without observation

In the early 1900s, considerable progress occurred after Albert Einstein developed his theories of relativity. These enduring equations link space and time, and dictate the motion of matter which in turn dictates the gravitational fields and waves within spacetime.

Soon after, in 1916, astronomers Karl Schwarzschild and Johannes Droste independently realised that Einstein's equations gave rise to solutions containing a "mathematical singularity", an indivisible point of zero volume and infinite mass.

Studying the evolution of stars in the 1920s and 1930s, nuclear physicists reached the seemingly unavoidable conclusion that if massive enough, certain stars would end their lives in a catastrophic gravitational collapse resulting in a singularity and the creation of a "frozen star".

This term reflected the bizarre relative nature of time in Einstein's theory. At the event horizon, the infamous boundary of no return surrounding such a collapsed star, time will appear to freeze for an external observer.

While advances in the field of quantum mechanics replaced the notion of a singularity with an equally bewildering but finite quantum dot, the actual surface, and interior, of remains an active area of research today.

While our galaxy may contain millions of John Michell's stellar-mass black holes—of which we know the whereabouts of a dozen or so—their event horizons are too small to observe.

For example, if our Sun were to collapse down to a black hole, the radius of its would be just 3km. But the collision of stellar-mass black holes in other galaxies was famously detected using gravitational waves.

Looking for something supermassive

The EHT's targets are therefore related to the supermassive black holes located at the centres of galaxies. The term black hole actually only came into use in the mid- to late 1960s when astronomers began to suspect that truly massive "dark stars" powered the highly active nuclei of certain galaxies.

Numerous theories abound for the formation of these particularly massive black holes. Despite the name, black holes are objects, rather than holes in the fabric of spacetime.

In 1972, Robert Sanders and Thomas Lowinger calculated that a dense mass equal to about one million solar masses resides at the centre of our galaxy.

By 1978, Wallace Sargent and colleagues had determined that a dense mass five billion times the mass of our Sun lies at the centre of the nearby galaxy M87.

But these masses, slightly revised since then, might have simply been a dense swarm of planets and dead stars.

In 1995, the existence of black holes was confirmed observationally by Makoto Miyoshi and colleagues. Using radio interferometry, they detected a mass at the centre of the galaxy M106, within a volume so small that it could only be, or soon would become, a black hole.

Today, around 130 such supermassive black holes at the centres of nearby have had their masses directly measured from the orbital velocities and distances of stars and gas circling the black holes, but not yet on a death spiral into the central gravitational compactor.

Despite the increased sample, our Milky Way and M87 still have the largest event horizons as seen from Earth, which is why the international team pursued these two targets.

The shadowy silhouette of the black hole in M87 is indeed an astonishing scientific image. While black holes can apparently stop time, it should be acknowledged that the predictive power of science, when coupled with human imagination, ingenuity, and determination, is also a remarkable force of nature.


Explore further

Black holes: picturing the heart of darkness

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Apr 11, 2019
The long journey to an image of not a BH, but a toroidal plasmoid. A decades long buzzkill for the Darkist acolytes.

Apr 11, 2019
There is a suspicious lack of EU adherents talking about this image in public. It does pretty much look like what mainstream science predicted it would. Though everyone long ago thought that the earth was the center of the universe because they could see the stars and planets revolving around us. Could this image be something close to what they think they see and not be exactly that? Not sure what angle we are seeing, but it does look like a toroidal plasmoid or perhaps a hypertrochoidal magnetic field around a very large, dense mass.

Apr 11, 2019
The long journey to an image of not a BH, but a toroidal plasmoid. A decades long buzzkill for the Darkist acolytes.


Another stupid comment.

Apr 11, 2019
There is a suspicious lack of EU adherents talking about this image in public. It does pretty much look like what mainstream science predicted it would. Though everyone long ago thought that the earth was the center of the universe because they could see the stars and planets revolving around us. Could this image be something close to what they think they see and not be exactly that? Not sure what angle we are seeing, but it does look like a toroidal plasmoid or perhaps a hypertrochoidal magnetic field around a very large, dense mass.


Read the article. The mass is such that it can only be a black hole. And the image looks similar to the simulations, because they used a BH in the simulations. That is lensed light. No plasmoid woo. The reason there is little comment from EUists is due to their scientific illiteracy. The same was also true for the gravitational wave detections, and the neutron star merger, in particular.

Apr 11, 2019
If you expect more out of gravity theory than GR supremacism offers, and you are open-minded and smart about it, you may see indications of consciousness-type behaviors in non-living matter, you may see how some natural error correction mechanisms might work, you may see potential signs of counter-entropic effects, all pretty much flowing out of the idea of replacing holy "curved space" smoothness extremism with something that does not look for all the world like it despises quantum gravity in spirit from the get-go, as in spirit it is quite sure it can get away with such things using brain-washing mass-media repetition. But the current gravity supremacists won't enjoy that, their religious institutions won't enjoy it, so you can expect an absurd amount of resistance still to overcome.

Apr 11, 2019
If you expect more out of gravity theory than GR supremacism offers, and you are open-minded and smart about it, you may see indications of consciousness-type behaviors in non-living matter, you may see how some natural error correction mechanisms might work, you may see potential signs of counter-entropic effects, all pretty much flowing out of the idea of disposing holy "curved space" smoothness extremism. But the current gravity supremacists won't enjoy that, their religious institutions won't enjoy it, so you can expect an absurd amount of resistance still to overcome.


Nothing is trying to overcome it. Only cranks.

Apr 11, 2019
"Nothing is trying to overcome it. Only cranks."

Oh right, your the one who blew up when I said matter tends to retroflect gravity. It's just you, gaslighting me again. The smell of stinko loserville is growing from the orifices of your gravity gang.

Apr 11, 2019
"Nothing is trying to overcome it. Only cranks."


Was it not retroflection that triggered you? Did suggesting a static wave set you off, what??????
Speak now then bust off because I'm not interested in talking to you at all. Dark matter is all about the secrets of gravity-clown loserville.

Apr 11, 2019
"Nothing is trying to overcome it. Only cranks."

Oh right, your the one who blew up when I said matter tends to retroflect gravity. It's just you, gaslighting me again. The smell of stinko loserville is growing from the orifices of your gravity gang.


Lol. GR has yet again been confirmed in its biggest test so far, and you are prattling on about some unpublished woo. Get a life.

Apr 11, 2019

Read the article. The mass is such that it can only be a black hole. And the image looks similar to the simulations, because they used a BH in the simulations. That is lensed light. No plasmoid woo. The reason there is little comment from EUists is due to their scientific illiteracy. The same was also true for the gravitational wave detections, and the neutron star merger, in particular.

So you believe in singularities? Infinite density? This is better explained by an ether theory where something massive enough that undergoes field coherency could have enough inertia and acceleration-back to the ether- to overcome Cartesian, polar, magnetic magnitude and literally vanish from the visible world.

Apr 11, 2019
So you believe in singularities? Infinite density? This is better explained by an ether theory where something massive enough that undergoes field coherency could have enough inertia and acceleration-back to the ether- to overcome Cartesian, polar, magnetic magnitude and literally vanish from the visible world.


Lol. Aether theory! M & M got rid of that ridiculous crap in 1887. And many experiments since show it to be pure woo. And you need to realise that the singularity is an inevitable consequence of GR maths. It cannot exist in reality. It is therefore where we know GR breaks down. Something else is needed. And it ain't aether woo! Nobody writes about that crap in the scientific literature any more.

Apr 11, 2019
"Get a life."

Get a new blood supply, dark matter sucker. GR and curved space are near-sighted galactic crap and you know it.


Apr 11, 2019
"Lol." "Woo."

You get so infantile, sociopathic and pig-insecure about your secret gravity failure called dark matter. 2nd request re your special losing quest to gaslight me endlessly with nothing but Einstein drag-queen pom-pom logic. So far it's only you alone who needs to block me, boring-woo-boy.

Apr 11, 2019
"Lol." "Woo."

You get so infantile, sociopathic and pig-insecure about your secret gravity failure called dark matter. 2nd request re your special losing quest to gaslight me endlessly with nothing but Einstein drag-queen pom-pom logic. So, you alone need to block me, boring-woo-boy.


Idiot. Where is your crap written up? Stop making up stories, you clown.

Apr 11, 2019
Castle-ninny, hero of the stupid in gravity, strikes again. Anything but your gravity is a slur against all of your underground necro-maniac special relatives, no doubt. The boy who lost his cerebrum in a horrible Einstein-cow-horn-blowing exercise, is acting up again. You should block me or find someone for special pom-pom ops reinforcement. That should be revealing, wormhole-boy. Or else, keep false-flagging against the facts, gravity-bomber.

Apr 11, 2019
Castrata-domingo the special needs gravity bomber gaslight boy can't find any one else willing to back up his sociopathology here? Can't believe it! Incredible. What a spongy putz.

Apr 11, 2019


Lol. Aether theory! M & M got rid of that ridiculous crap in 1887. And many experiments since show it to be pure woo. And you need to realise that the singularity is an inevitable consequence of GR maths. It cannot exist in reality. It is therefore where we know GR breaks down. Something else is needed. And it ain't aether woo! Nobody writes about that crap in the scientific literature any more.

M and M didn't prove anything, either way. It wasn't even an experiment. Check out Dayton Miller's work. In the photoelectric effect, Einstein 1905, did away with the need for an ether with discrete quantized packets. Relativity and quantum mechanics are rehashed Greek Atomism. All phenomena is ether manifest as magnetism.

Apr 11, 2019
Everyone is bored to death by arguments between incompetent general relativity cheerleaders and electric universe sock-puppets. It's loser takes all.

Apr 12, 2019
There it is, whether you deny it or not. A picture of a black hole.

It makes you all look like idiots, but that's what it is. Get over it.

Apr 12, 2019
"It makes you all look like idiots"

Because it's a waste of time and money, goofball button-eyed monkey-boy.

Apr 12, 2019
"It makes you all look like idiots"

Because it's a waste of time and money, goofball button-eyed monkey-boy.


Nope. That is merely your untutored opinion. Worthless.

Apr 12, 2019
Does this damn website have any moderation at all or do they just spend their time constantly rearranging the css?

Apr 13, 2019
@cantdrive85: can you give some figures of the magnetic field of said toroidal plasmoid and the corresponding emitted radiation frequency and intensity of the plasma inside it?

Apr 13, 2019
Everyone is bored to death by arguments between incompetent general relativity cheerleaders and electric universe sock-puppets. It's loser takes all.


Then link us to the alternative. In the peer-reviewed scientific literature. Or be quiet.

Apr 13, 2019
Castrata-domingo the special needs gravity bomber gaslight boy can't find any one else willing to back up his sociopathology here? Can't believe it! Incredible. What a spongy putz.


Says the thicko whose Nobel worthy 'hypothesis' only exists in his own mind! Show us the science, Dunning-Kruger boy.

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