We are literally going to get our first ever image of Sagittarius A* (the supermassive black hole at the center of the milky way) tomorrow and I'm so fucking excited to see that blurry image omg

By the way, Sagittarius A* is pronounced Sagittarius A Star if you want to talk about it out loud, but it is NOT a star at all.

Sagittarius A* is not currently considered to be an AGN (active galactic nucleus) however it IS still feeding on gas and dust that spirals into it from the interstellar medium in the central bar of the Milky Way, and even from some gas from the solar wind of the 30 or so stars that directly orbit it in a tight cluster.

HOWEVER the REALLY cool thing about black holes is that LIGHT can orbit them!!! Not stabley of course, eventually the light will either find itself on an inwards trajectory or an outwards one. If you were able to stand in this zone, you'd be able to see the back of your own head looking forward because that would just be a valid geodesic in the local geometry. There's a sphere of orbiting light around that black hole!

What we're going to SEE when we get the image though, won't be the actual event horizion. Instead, we're going to be able to see a radius juuuuust bigger than the photon sphere, where light can just graze past a doomed trajectory and then continue on to hit our patient telescopes. When we get to look at the photos we will see a blurry ring of light, mostly radiated by an incredibly hot accretion disk around Sagittarius A*

As it turns out, the image we recieve of our local supermassive black hole will probably end up looking like a blurry ring of light, roughly like the artist's renditions from Interstellar. What an awesome and beautiful tear in reality, we're about to witness.

We are about to witness a ring of light, a shadow of an actual event horizon. Tomorrow. Fuck I'm so excited.

:3< @starwall why didn't þey take a picture of it sooner like. Just grab your phone & zoom in reeeaaal far

@starwall that's a lot bigger than I realized.

... Heck. That's spooky.

@starwall now I'm wondering, what are the actual tidal forces like nearish the event horizon? I understand they get mellower as black hole mass increases.

How close could a planet or dwarf planet or whatever orbit?

@starkatt Not terribly close. The closest stable orbit matter can get to the event horizon is 3 schwarzschild radii, and furthermore, the Roche limit of Sagittarius A* is about 200 times its radius.

@starwall while trying to find info about the Roche limit of black holes, I did run across info about this binary system where a white dwarf orbits a (probable) black hole every 28 minutes, at 2.5 times the earth moon distance. The star is getting stripped though so it doesn't really count.

@starwall this is so cool?????? please talk about space forever everything you say is so interesting and amazing,,,,

@ida It DOES! It's got all kinds gas and dust of the interstellar medium within the core, along with the stellar winds of like 30 nearby stars to feed on.

@ida It's not currently like devouring suns or anything, but it's still got a really hot disk around it.

@starwall i am very excited about this now please keep my posted

@J I will make my big old post about it on @starwall so be sure to follow me there!

@goat @starwall he'll yeah, i think there's a station out there now iirc

@fey No we don't have any real pictures of it YET. tomorrow we will be getting our first REAL picture of it.

@starwall holy crap I was just shitposting earlier but that does look like an eye!

@MissionControl we are going to see what it really looks like in like, less than 24 hours.

@starwall is it weird that i knew about this bc of a greg egan story (planck dive),

@starwall being anywhere remotely near a black hole would be so fucked up and weird

@starwall this is reminding me that i need to finish relativity thread

@dankwraith The closest known black hole to us is only 3,000 light years away if we're feeling ambitious.


some coders pronounce "*" as "splat".

i have no joke here, i just like saying "Sagittarius A Splat"

@starwall it can be a star if it wants to

i'm certainly not about to tell it no!

@Felthry Sagittarius A* is a star to me, though it certainly doesn't shine like one.

@starwall Well, black holes are just super heavy stars chef you think about it 🤔.

@TeethTeethTeeth Sometimes, a star isn't directly being tidally torn to shreds by a black hole, and instead just orbits it closely like a planet around a regular star.

@starwall @TeethTeethTeeth

There are a couple of stars nearby that take 15 years or so to orbit and that's one of the ways they've been trying to pin down the mass of Sagittarius A*.

@starwall so like... how much of an image??? like, this is fucking monumental, right? or

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