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I'm literally abt to hop on a plane for the rest of the day, but here are a few things that make this #EHTBlackHole press release monumental to me from the perspective of an astrophysicist who studies active black holes. 
1. It's still true that we can't *see* a black hole. What sight-abled folx are seeing in this image is the shadow of the black hole (what I typically call "SOS" signals from the material about to fall onto it). This process of material infall onto a black hole is called accretion
2. We've observed black holes for decades using the fact that infalling matter releases copious amounts of radiation (light) before crossing the event horizon. Black holes dominate high energy light like X-rays bc of accretion. This is a composite image of M87. @NASAHubble
3. The #EHTBlackHole result is monumental bc of the exquisite resolution at which we can discern this light. The analogy Daniel Morrone made was that it was like reading the date on a quarter that's in LA from DC. So we're observing the actual *event horizon* of M87s black hole.
4. No information from anything within that event horizon, defined as the radius at which not even light can escape the gravitational pull of a black hole, can be obtained. So this is the last stop before oblivion.
5. The image itself is stunning and a testament to international collaboration, innovative engineering and savvy data science interventions. But the fact that we can actually directly measure the mass and spin of this black hole is stunning. SO much more to read and process!
I gotta hop on this flight, but ya'll keep reading. There's so much more to learn and be excited about from these #EHTBlackHole results. Follow @ehttelescope, but also @reneehlozek @IBJIYONGI @AstroKatie +++ are all putting out amazing content abt this. I'll be back tonight!
Layover #EHTBlackHole thoughts: The #EventHorizonTelescope has *two* primary targets: M87 + Sagittarius A* (which is the black hole at the center of our Milky Way galaxy). M87 accretes more and thus has a significantly stronger signal that Sgr A* despite being MUCH further away.
So we should expect as they are able to model and interpret the #EventHorizonTelescope results from Sgr A* that we'll get another set of exciting results. It took TWO YEARS after the observations were obtained to get these results.
While M87 and Sgr A* are both supermassive black holes, they have vastly different accreting regimes and putative black hole masses. M87 was previously estimated to be at several BILLION times the mass of the Sun; Sgr A* is abt a MILLION times the mass of the Sun. Very different.
So once we have both (improved) results, we compare them for two very different black holes and see what we find. The six papers that the #EventHorizonTelescope collaboration has already released have exquisitely (read more precisely) pinned down a black hole mass for M87.
