An amazing announcement occurred this week: scientists working with what is called the Event Horizon Telescope (“EHT”) had captured
A Few Facts About the M87 Supermassive Black Hole
The image the EHT captured is of the supermassive black hole at the center of a galaxy called Messier 87 (“M87”).
The M87 Galaxy is huge – thought to hold trillions of stars. As a comparison, the Milky Way has around 150 billion stars. M87 anchors a cluster of galaxies known as the Virgo Cluster, of which the Milky Way is a member.
Black holes form when a massive star (more than 20x size of the Sun) has used up its fuel, is at the end of its life, and collapses in upon itself. This collapse also causes the star to explode, a so-called supernova. The gravity due to the extreme mass and density is so great that the escape velocity (the speed at which something needs to travel to escape the gravity of an object) is greater than the speed of light. According to physicist Janna Levin all this dense mass results in “space-time effectively spilling toward the crushed center. Racing at its absolute speed, even light gets dragged down the hole, casting a shadow on the sky. That shadow is the event horizon, the stark demarcation between the outside and anything with the misfortune to have fallen inside.”
A black hole with the mass of the sun would be about 6km wide (compared with the 1.4 million kilometer width of the sun). The supermassive black hole at the center of the Milky Way (called Sagittarius A*) is
IFOD on Supermassive Black Holes.
The Amazing Technological Achievement of the EHT
Even a black hole as massive as the M87 is unbelievably hard to see. It is 55 million light years away and even with its massive size the EHT scientists said that observing it was like looking a piece of fruit on the moon from earth. If the black hole was merely black, it would be invisible from such a distance. Fortunately, M87’s black hole is illuminated by super hot debris moving nearly at the speed of light orbiting around their event horizons.
How did they did they observe this relatively small black hole from such a distance? Sheperd Doeleman, the director of the EHT, proposed in his doctoral thesis at MIT that in order to take a picture of a black hole a telescope the size of the earth would be needed. He knew that building a telescope that big is not feasible, so he instead proposed combining telescopes all across the earth to capture an image. In a truly amazing feat, EHT took images from 8 radio telescopes located in Hawaii, the South Pole, Arizona, Chile, and Spain.
According to Cosmos Magazine, the EHT is “linked by a method called very long baseline interferometry. This allows images from several telescopes to be combined, mimicking the resolution of a single dish much larger in diameter. For the Event Horizon Telescope, the scientists carried this idea to its extreme, by combining data from telescopes in Hawaii, Arizona, Chile, Spain, and the South Pole to create a virtual telescope the size of the entire Earth. But to make it work, the scientists first had to connect hyper-accurate atomic clocks to each facility, so that each one’s observations could be very precisely timed. Then, five petabytes (that is, 5000 terabytes) of data were collected and transported to computing facilities in Germany and the US.”
The images used for the image of the black hole were taken in April 2017 and supercomputers have been crunching the data to produce the image for nearly two years. Girl Power! Read about the computer scientist who created the crucial computer algorithm (after six years of work) that helped make the image a reality here.
General Relativity is Confirmed (again)
Proposed in a paper Einstein published in 1915, General Relativity states that what we know as gravity arises from the curvature of space and time (or spacetime). In other words, objects with mass (or energy) bend the fabric of spacetime and this curvature of spacetime is what causes what we perceive as gravity. IFOD on General Relativity.
While serving on the Russian front in WWI, German physicist Karl Schwarzschild mathematically determined that General Relativity meant that what we now call black holes would occur if enough mass were fit into a small enough radius. Thus, black holes were first discovered mathematically. IFOD on Is Mathematics Invented or Disovered?
Over the past 100 years the existence of black holes has become more and more certain with indirect evidence:
- to be held together, the mathematics of General Relativity concludes that supermassive black holes must be at the center of most (or maybe all) galaxies
- scientists have observed stars being cannibalized by black holes
- stars have been observed orbiting black holes
- recently, gravitational waves have been detected when two black holes collided. IFOD on LIGO D
etectorsand Gravitational Waves.
However, for all the indirect evidence of black holes, we’ve never actually seen one. Until now. We now have direct evidence of black holes. This picture of a black holebyet again confirms General Relativity.
I find it unbelievably inspiring that in an age when many Americans have eschewed the teachings of science (anti-vaccine movement, denial of climate science, denial of evolution, to name a few), scientists can produce such a stunningly blinding example at the scientific achievements of our species – that we could have mathematically figured out something as insanely bizarre as a black hole and then actually take a picture of one 55 million light years away.
When asked about his thoughts on seeing the image of the black hole for the first time, the director of the EHT replied: “We saw something so true.”
Related IFOD on Hawking Radiation
A lot of comments among Tolkien fans about how much this looks like the eye of Sauron. Scary. How did Peter Jackson know???
This is one of my favorite IFODs. Although not a scientist, I am fascinated by such information. Thanks for providing this insight into the black hole photo M87.
It is so exciting for me to see the reaction this announcement is garnering from non-scientists – especially here in flyover land. In my office building everyone is talking about it – in hallways, elevators, lunchrooms. My coastal science pals think the whole middle of the country is comprised of the great unwashed engaging in a relentless anti science conspiracy campaign. SO happy to be able to show them that once again, they are wrong.
I am so glad that you wrote about this – it is a better explanation than I have found elsewhere about black holes and how they got the picture.
I totally agree with all this IFOD says about this being completely remarkable and exciting. And I love that something astronomical was on the front pages of all major papers yesterday — not just the story but the picture! One point I want to make, though, is that the “picture” is created for human viewing and doesn’t really exist in the real world.
The scientists and their computers have taken various radio waves (captured by radio telescopes all over the world) and assigned to them different visible frequencies of light so that we humans — who can’t see radio waves — can see an image. (Without this slight of hand, we couldn’t see these magnificent findings anymore than we can “see” FM 95.5 coming towards our own radios.) It gets to a more metaphysical discussion on what it means to “see” something.
I recall a story about Feynman who had an interesting interaction with someone who asked how he could say that electrons exist when he cannot see them. Feynman asked how this person knew the pope existed and he said “because I see him on TV”. Feynman responded, that’s also how he knew electrons exist. (older model TVs with tubes use electron beams to form images… )
Scientists often make visual displays of complex, otherwise inaccessible data to interface with human senses. It is really not slight of hand… And if they distort the data in any way to alter the scientific interpretation, their careers can be seriously damaged or ended.
Totally agree. And “slight of hand” is probably too loaded a term. But If you were standing next to the Pope, you’d see the Pope. If you were (uncomfortably) standing next to a black hole, you would not see the photo on the front pages of all the newspapers. My point is not that they are being deceptive but that “seeing a black hole” involves unbelievable technological advances including creating a visible image from radio waves. You state that that is often done. I agree, but I think most people don’t realize that.