First, this is totally harmless. Tiny and far away, shrouded with dust and gas. They can only see it using radio waves that go through the dust. And the photo of course changes nothing, we've know it is there for a long time away. This is a screenshot from the press conference:

And over four separate days:

Short summary here

A good summary:

The EU version of the press conference is here:

This is another article I did to support people we help in the Facebook Doomsday Debunked group, that find us because they get scared by various stories. I've had a few people ask me if we are in any danger from this black hole.

It can't harm us in any way. There are stars orbiting the black hole in the center of our galaxy. They do not get sucked in irresistibly, that's something made up for Star Trek and just isn't true. You have to be close enough to have an orbital velocity faster than the speed of light before you can fall in.

The photo is of the supermassive black hole at the center of M87. This black hole is at a great distance from us, a distant galaxy about 55 million light years away. It is so large that if you had a black hole in our solar system that large it would extend to four times the distance to Neptune.

Yet it is so far way that it is similar in size to a mustard seed in Washington as seen from Brussels.

This is amazingly tiny for us to see at a distance so far away that the light left it fifty five million years ago.

It’s about 300,000,000,000,000,000,000 miles (16.8 mpc in miles it's about 3 e+20 that means 3 followed by 20 zeroes).

The dark bit in the center here is a spot where light can't escape. If it was anything else then the center would be bright rather than dark so it is a direct observation of the blackness of the black hole.

This is something scientists will remember as a landmark observation centuries from now.

The data they used to reconstruct this image occupied SIX CUBIC METERS of disk drives!

They had to pick a day when all their telescopes were able to see it at once, from the south pole all the way to the north pole, because that is how interferometry works. The photos have to be absolutely simultaneous precisely timed to a minute fraction of a second - or you can’t mimic the effect of a larger telescope. They also had to have good weather at all the locations of all the telescopes. There was only one opportunity in the year for this.

Then - the data at the south pole had to be flown to the center for processing the data, which they couldn’t do until six months after the photo because of the south pole winter. The amount of data here, petabytes, is an amount that’s impossible to send over the internet. They had to transport it physically in hard drives.

Its mass is about 6.5 billion solar masses. Using this black hole radius calculator, that makes the diameter about 0.0020296 light years or 17.8 light hours or 128 au (one au is the distance to the sun). The distance from the sun to Neptune is around 30 au.

They observed it for four days.

It didn't change significantly. The contrast is as large as expected. The ring is much brighter at the bottom side. This can only happen if something in the source is rotating - the black hole or the matter. There isn't enough to work out the exact speed but the direction they know is clockwise as seen from Earth.

They expect to be able to finish processing the data for Sagittarius A, the black hole at the center of our galaxy, in the near future. There are many near future upgrades of the radio telescopes used in the observation which will improve the images in the future.

They released the M87 photo first because it was easier to photograph. They didn't know it would be quite so large and it is also very stable just sitting there (hardly changed over four days). While our Sagittarius A is constantly changing even in eight hours, he said it's like a toddler who can't stay still. So it's harder to photograph.

They simulated the effect of jets and accretion disks and whatever they did they got the same kind of photo, the GR dominates everything else because of the light blending at the high radio frequencies they use - you can observe the accretion disk closer to the inner region but the jet and accretion disk and other features are blended together by light blending.

It is a mix of light from the accretion disk that's falling in and light from the jet which is fired out at great speed along its rotation axis. They deliberately chose a wavelength that has both so as to get as close as possible to the black hole. What is photographed is not stictly speaking the event horizon but a "shadow" region that extends a bit beyond it. Around 10% beyond in simulations in this paper. But then there is scatter from the image resconstruction process as well.

The structure and extent of the emission preferentially from outside the photon ring leads to a <~ 10% offset between the measured emission diameter in the model images and the size of the photon ring. The scatter over a large number of images, which constitutes a systematic uncertainty, is found to be of the same magnitude.

They simulated it with a general relativity model in the center of these images. What they photographed is the very narrow circular “photon ring” around the black hole. In their simulations it looks circular at all inclinations of the black hole axis. But parts of it look brighter depending on the angle of the axis and jet. This is because the material in the ring is moving rapidly and the approaching side of it is boosted in brightness and the receding side of it dimmed in a process called “doppler beaming”. It’s due to charged particles in the material that interact with the magnetic field in ways that lead to more light (synchotron radiation) being sent in the direction of travel of the ions.

“The ring is brighter in the south than the north. This can be explained by a combination of motion in the source and Doppler beaming. As a simple example we consider a luminous, optically thin ring rotating with speed v and an angular momentum vector inclined at a viewing angle i > 0° to the line of sight. Then the approaching side of the ring is Doppler boosted, and the receding side is Doppler dimmed, producing a surface brightness contrast of order unity if v is relativistic.”

It’s the same phenomenon as you get with jets. In this photograph of 3C31, the upper jet in the photo is pointed a bit towards us and the lower one is pointed away, and so the upper one is brighter because of the doppler beaming

Relativistic beaming - Wikipedia

They call it M87* - the * means exciting object in M87, not that it's a star.

They found nothing that contradicts Einstein's theory. Everything fits amazingly perfectly to the simulations.

They used millimeter wavelength radio waves.

This video is about how they took the photo, by Katie Bouman who devised the algorithm they used that was the key to the whole project

This is a photo of her taken when she first saw the image take shape on her laptop

Watching in disbelief as the first image I ever made of a black hole was in the process of being reconstructed.

From her Facebook timeline

More about her here

• The woman behind first black hole image

What they see is consistent with Einstein and is the simplest. There are more exotic theories not excluded but they are also more complicated than Einstein's theory.

They can exclude a few right away - a naked singularity (with no event horizon, so you could go as close as you like and still be able to escape) or superspinar (rapidly rotating supermassive star) is impossible. They are also just about certain that it isn’t the mouth of a Wormhole (familiar from TV series like Star Trek) where the black hole connects to another region of space.

Wormhole-demo.png - Wikimedia Commons This shows the idea of a wormhole. It is schematic - the space isn’t really curved around like that - imagine the outside region as flat and the wormhole makes a shortcut between the two points.

A boson star (a strange kind of almost transparent star made of axions or other not yet discovered particles) would require a different mass from that derived independently and a gravastar (a star with a false vacuum interior and true vacuum exterior) would have a different accretion disk variability).

Nevertheless, some conclusions can drawn already. For instance, the shadow of a superspinar is very different from that of a black hole, and the EHT2017 observations rule out any superspinar model for M87. Similarly, for certain parameter ranges, the shadows of spherically symmetric naked singularities have been found to consist of a filled disk with no dark region in the center; clearly, this class of models is ruled out. In the same vein, because the shadows of wormholes can exhibit large deviations from those of black holes, a large portion of the corresponding space of parameters can be constrained with the present observations.

A comparison of EHT2017 data with the boson star model, as a representative horizonless and surfaceless black hole mimicker, and a gravastar model as a representative horizonless black hole mimicker, will be presented in Olivares et al. Both models produce images with ring-like features similar to those observed by EHT2017, …. The boson star generically requires masses that are substantially different from that expected for M87, while the gravastar has accretion variability that is considerably different from that onto a black hole.

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

There a boson star is nothing to do with the Higgs boson. There are many kinds of bosons, for instance photons are bosons. So are some special kinds of atomic nuclei like helium 4 nuclei. Boson - Wikipedia

A boson star is a strange kind of star probably transparent but not black. Perhaps made of axions, a kind of dark matter or some other undiscovered particle. See Exotic star - Wikipedia

For higher resolution, they need to simulate a larger telescope and so have to go into space. In the press conference they said to expect papers about how to do this in the near future. But for example with a radio telescope on the Moon you’d get 30 times the resolution if you could sync it up with Earth telescopes in the same way.

Meanwhile though, they are going to upgrade to larger radio telescopes on Earth so that they can collect more photons. Didn’t go into detail in the press conference - but that would mean being able to image fainter objects, but not smaller ones - and particuarly to be able to get shorter snapshots less blurred by motion of the black hole accretion disk. Expect to see movies of the black holes some time not too far in the future like those four images already released.

For the mass and diameter:

Techy details - I’m using the values in this paper:

“Based on these, we adopt a distance of

to M87″ (end of section 8.1)

“Accounting for this uncertainty explicitly, the resulting black hole mass is

(10, conclusions) of First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole

The entire image is about 20 pixels across before smoothing:

It used to be that we couldn’t even resolve nearby stars, they were just a single pixel.

Nowadays with adaptive optics we can resolve nearby large stars even from the ground, with photos of sunspots on Betelgeuse for instance. But at the distance of M87, 55 million light years away it's about 20 pixels across and that's for a black hole region that would extend to double Neptune's distance from Earth (it may be more I haven't read the papers yet) and an effective aperture equal to that of the Earth.

If they had another telescope in space it could be higher resolution. Add one on the Moon and that's 30 times the resolution so then the same image would be 600 pixels across.

This is a high resolution image of Betelgeuse taken in 2009 - there may be higher resolution ones

The paper says ". If these spotty structures are similar to those observed on the Sun, then they could be faculae which are bright zones surrounding dark convection cells. Their presence on Betelgeusewould show that a magnetic field plays an important role as it is the case for the Sun."

The simulations were of a disk not seen precisely face on. The varying in brightnesss I think is a gravitational lensing effect.

But there are many papers on the topic released simultaneously with the announcement and they surely have material on it, just not had time to read them yet.

WHAT WOULD HAPPEN IF YOU FELL IN?

First, black holes do not suck things in from a distance. Forget all those Star Trek episodes where they are irresistably pulled in by a black hole. Even if you are just outside the event horizon - even if you were only twenty light hours away from it, you’d be orbiting it at a speed of nearly the speed of light. But you would not fall in.

We can see stars doing this in the center of our own galaxy. Here are some stars orbiting Sagitarius A. Notice how as they come in towards the invisible central point they whip around and zip out again. If you were to fly almost directly towards a black hole in a star ship, but not directly at it, you would whip around in the same way. And because you are under free fall you would not feel any gravitational tug on you inside the spaceship. If you didn’t have artificial gravity of some sort (e.g. by spinning) you’d be in free fall like the astronauts in the ISS all the way.

Now you’ve probably heard of spaghettification. The way tidal effects would rip you apart if you approach a black hole too closely?

That is true of small black holes. But for really big black hole like the one in M87 there isn’t any significant tidal effect at the event horizon and it is much gentler.

If you had a large dormant black hole without an accretion disk then Earth could orbit it fine with no problems at all. Here is an animated gif showing what it would be like with Earth orbiting a black hole.

Click here to watch it animated. From Journey into a Schwarzschild black hole

In this animation Earth is not changing shape, this is just a gravitational lensing effect. In this case it is orbiting a black hole of mass two thousand suns to give it a radius the same as that of Earth and Earth is orbiting at three times the radius of the black hole (to its event horizon), the minimum stable circular orbit.

With a really big black hole like the one at the center of our galaxy, you would survive for a while before you fell into the center.

Even after you cross the event horizon you would have a couple of hours of your life left to enjoy the inside of the black hole, about the same length of time as watching a long movie. But of course you couldn't tell your colleagues outside what you saw in the last two hours of your life.

In this description the authors describe a one billion solar mass black hole as if it was the black hole in the center of our galaxy - that is out of date as Sagitarius A is only 2.6 million solar masses. But the M87 one is more than two thousand times more massive and a thousand times further away.

So this is a reasonable description except this is for a non rotating black hole, and it is also for one without an accretion disk, and a little smaller than the M87 one. This is from Gali Weinstein's answer to Could a person survive falling into a galactic black hole? which I can reproduce by the Quora license but can’t modify (see tos ). It’s retelling of the story in a 1975 book by John Archibald Wheeler and Edwin Taylor :

Two hours before the end. We are now at r = 2.13M, just outside the event horizon and our speed is 97 percent that of light as measured in the local black hole reference frame that we are passing. Changes in viewing angle (aberrations) are now extremely important.

Wheeler and Taylor explain that anything we see after an instant from now will be secretly taken to our grave because we will no longer be able to send any information out to our surviving colleagues. Although we will be “inside” the black hole, not all of the sky in front of us appears entirely dark. Our high speed causes light beams to arrive at our eyes at extreme forward angles. Even so, a huge disk in front of us is fully black — a substantial fraction of the forward sky.

Behind us we see the stars grow dim and spread out; for us, their images are not at rest but continue to move forward in angle to meet the advancing edge of the black hole. This apparent star motion is again a forward-shift due to our increasing speed.

But there is a more noticeable feature of the sky: we can now see second images of all the stars in the sky surrounding the black hole due to gravitational lensing. These images are squeezed into a band about 5 degrees wide around the image of the black hole. These second images are now brighter than were the original stars. Surrounding the Einstein ring of second images are the still brighter primary images of stars that lie ahead of us, behind the black hole. The band of light caused by both the primary and secondary images now shines with a brightness ten times that of Earth’s normal night sky.

We have already passed the horizon.Approximately two minutes before oblivion. The black hole now spreads over the entire forward sky. Behind us, star images are getting farther apart and rushing forward in angle. Only 20 percent of star images are left in the sky behind us. In a 10-degree-wide band surrounding the outer edges of the black hole, not only second but also third and some fourth images of the stars are now visible. This band running around the sky now glows 1000 times brighter than the night sky viewed from Earth

The final seconds. The sky is dark everywhere except in that rapidly thinning band around the black disk. This luminous band — glowing ever brighter—runs completely around the sky perpendicular to our direction of motion.

At three seconds before oblivion, it shines brighter than Earth’s Moon. As a result of gravitational lensing, new star images rapidly appear along the inner edge of the shrinking band as higher and higher-order star images become visible from light wrapped many times around the black hole. The stars of the visible universe seem to brighten and multiply as they compress into a thinner and thinner ring transverse to our direction of motion. Tidal accelerations due to tidal forces become pronounced: you feel radially stretched due to a difference in acceleration between your head and your feet, along with a compression from side to side.

Wheeler and Taylor end their movie script by saying that, only in the last fraction of a second on our wristwatch, do tidal forces become strong enough to end our journey and our view of that awesome ring bisecting the sky.

Gali Weinstein's answer to Could a person survive falling into a galactic black hole?

This animation shows what it would be like to fall into a black hole of around five million solar masses, the time shown in seconds in the clock at bottom right and the inset to the left shows a map of your path into the black hole. The green zone is a safe one where circular orbits are stable, the yellow one is risky, circular orbits are unstable - you could still orbit it but just the tiny thrust on your maneuvering thrusters sends you either into the black hole or off into space. The orange zone is danger, no circular orbits are possible at all but if you had a vastly powerful rocket you could hover here, and red means no escape.

There are many more videos on this page

• Journey into a Schwarzschild black hole

FIND OUT MORE

Article about it here by Shep Doeleman (EHT Director):

Focus on the First Event Horizon Telescope Results

It links directly to the academic papers.

Short video with the scientists talking about it:

Black hole picture 'a dream come true'

BBC article here

First ever black hole image released

There is a more detailed article about it in Astronomy . com:

" The observatory’s other main target is the black hole at the center of the Milky Way, Sagittarius A*. While it sits 1,000 times closer than M87, it’s also roughly 1,000 times smaller, so it takes the same amount of observing power. But because it’s smaller, the material swirling around its event horizon moves much faster, completing one circuit every few minutes, as opposed to a few days to circle M87.

"What’s more, astronomers aiming at Sagittarius A* must look through the disk of the galaxy, and are subject to more dust and other interfering material. But they still expect to release images of our galaxy’s black hole in the near future.

Even more exciting are the repeat images of M87 and other black holes yet to come. By watching how the black hole does or doesn’t change with time, astronomers can learn about stable features of the black hole, and watch how material disappears past the event horizon."

Event Horizon Telescope releases first ever black hole image

More details here:

Astronomers Capture First Image of a Black Hole - ESO, ALMA, and APEX contribute to paradigm-shifting observations of the gargantuan black hole at the heart of the galaxy Messier 87

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