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Powehi / First Image of Black Hole - A Radio Astronomer explains why the first image of a black hole is a big deal.
![, [-] Andromeda321 2161 points 1 day ago* S4 07 Radio astronomer here! This is huge news! (I know we say that a lot in astronomy, but honestly, we are lucky enough to live in very exciting times for astronomy!) First of all, while the existence of black holes has been accepted for a long time in astronomy, it's one thing to see effects from them (LIGO seeing them smash into each other, see stars orbit them, etc) and another to actually get a friggin' image of one. Even if to the untrained eye it looks like a donut- let me explain why! Now what the ima the event horizon, which is basically the "point of no return" after whic not actively sucking things into it like a vacuum, just like the sun isn't actively sucking the Earth into it.) As such, what we are really seeing here is not the black hole itself- light can't escape once within the event horizon- but rather all the matter swirling around and falling in. In the case of the M87 black hole, it's estimated about 90 Earth masses of material falls onto it every day, so there is plenty to see relative to our own Sag A* Now, on a more fundamental level than "it's cool to have a picture of a black hole," there are a ton of unresolved questions about fundamental physics that this result can shed a relatively large amount on. First of all, the entire event horizon is an insanely neat result predicted by general relativity (GR) to happen in extreme environments, so to actually see that is a great confirmation of GR. Beyond that, general relativity breaks down when so much mass is concentrated at a point that light cannot escape, in what is called a gravitational singularity, where you treat it as having infinite density when using general relativity. We don't think it literally is infinite density, but rather that our understanding of physics breaks down. (There are also several secondary things we don't understand about black hole environments, like the mechanism of how relativistic jets get beamed out of some black holes.) We are literally talking about a regime of physics that Einstein didn't understand, and that we can't test in a lab on Earth because it's so extreme, and there is literally a booming sub-field of theoretical astrophysics trying to figure out these questions. Can you imagine how much our understanding of relativity is going to change now that we actually have direct imaging of an event horizon? It's priceless! Third, this is going to reveal my bias as a radio astronomer, but... guys, this measurement and analysis was amazingly hard and I am in awe of the Event Horizon Telescope (EHT) team and their tenacity in getting this done. I know several of the team and remember how dismissed the idea was when first proposed, and have observed at one of the telescopes used for the EHT (for another project) f the hole itself, as gravity is so strong ligh but related to a special area called nnot escape. (It should be noted that the black hole is Ows IS t escape the wanted to shed a little more on just why this is an amazing achievement. Imagine placing an oran the moon, and deciding wa resolve it from all the rocks and craters wit ked eye- that is how detailed this measurement be t resolve the even Hawaii, by calibrating each getting rid of systematics, and then co-adding the data. This is so incredibly difficult I'm frankly amazed they got this image in as short get that resoluti ra ave k radio telescopes across the planet, from Antarcti (after it's shipped t rom the South Pole rn too slow down there time as they did! (And even this A f kly, I'm not surprised that obel Prize worthy accomplishmen f their two targets proved to be too troublesome t but today- getting that-why M87? Why is that mor resting than the blac ole at the f the galaxy? Wel urns out even wit insanely good resolut f the EHT, which is the best we c do until we get radio telescopes in space as it's limited by the size of planet, there are only two black holes we can resolve. Sag A, the supermassive black hole at the cen r galaxy that clock t "only" 25,000 light years away. M87's r own galaxy's supermassive blac in at 4 million times the mass of the sun, we can obviously do because it's relatively nea black hole, on the other hand, i hole. This meant its effective size was half as big as Sag A in in the sky despite being 2,700 times the distance (it's 54 million light years). The reason it's cool though is it's such a monster that it M87 emits these giant jets of material, unlike Sag A*, so there's going to now be a ton of information in how those work! billion times the ma f the or 1,700 "times bigg Anyway, this is long enough, but I hope you guys are as excited about this as I am and this post helps explain the gravity of the situation! It's amazing both on a scientific and technical level that we can achieve this! TL;DR- This is a big deal scientifically because we can see an event horizon and test where general relativity breaks down, but also because technically this was super duper hard to do. Will win the Nobel Prize in the next few years Edit: if you really want to get into the details, here is the journal released today by Astrophysical Letters with all the papers! And it appears to be open access! Edit: A lot of questions about why Sag A* wasn't also revealed today. Per someone l know really involved in one of the telescopes, the wea some of the signal at these frequencies), and the foregrounds are much more complicated for Sag A* that you need to subtract. It's not yet clear to me whether data from that run will still be usable, or they will need to retake it. wa s good a Il the telescopes a wa M87 observa even small amounts of water vapor air absorb](https://i.kym-cdn.com/photos/images/original/001/480/753/0a9.png)
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