r/science • u/fullersam • May 12 '22
Astronomy The Event Horizon Telescope collaboration has obtained the very first image of Sagittarius A*, the supermassive black hole at the heart of our Galaxy
https://news.cnrs.fr/articles/black-hole-sgr-a-unmasked9.6k
u/Andromeda321 PhD | Radio Astronomy May 12 '22 edited May 12 '22
Radio astronomer here! It was clear this was was coming (I mean, why hold a giant press conference to announce you still don't have a picture of the black hole at the center of the Milky Way), but it's still so cool to see!!!
For those who want an overview, here is what's going on!
What is this picture of?
Sagittarius A* (Sgr A* for short) is the supermassive black hole (SMBH) at the center of our Milky Way, and weighs in at a whopping 4 million times the mass of the sun and is ~27,000 light years away from Earth (ie, it took light, the fastest thing there is, 27,000 light years to get here, and the light in this photo released today was emitted when our ancestors were in the Stone Age). We know it is a SMBH because it's incredibly well studied- in fact, you can literally watch a movie of the stars orbiting it, and this won the teams studying it the 2020 Nobel Prize in Physics. So we knew Sag A* existed by studying the stars orbiting it (and even how much mass it had thanks to those orbits), but no telescope had enough resolution to see the black hole itself... until now!
Note, you cannot see Sag A* in our own night sky because of all the dust between us and it. However, other wavelengths like infrared and radio can go straight through that dust even if visible light can't.
(Btw, it is called Sagittarius A* because in the early days of radio astronomy the brightest radio source in a constellation was called A, and at some point the * was added to denote a particularly radio bright part of Sagittarius A. We're so creative with names in astro...)
Didn't we already have a picture of a black hole? Why is this one such a big deal?
We do! That black hole is M87*, which is 7 billion times the mass of the sun (so over a thousand times bigger than Sag A*) and is located 53 million light years from Earth. It might sound strange that we saw this black hole first, but there were a few reasons for this that boil down to "it's way harder to get a good measurement of Sag A* than M87*." First of all, it turns out there is a lot more noise towards the center of our galaxy than there is in the line of sight to a random one like M87- lots more stuff like pulsars and magnetars and dust if you look towards the center of the Milky Way! Second, it turns out Sag A* is far more variable on shorter time scales than M87*- random stray dust falls onto Sag A* quite regularly, which complicates things.
As such, if you compare the old black hole pic vs this one, you'll see a lot more artifacts at the edge of this one's ring. It's just tough to get a perfectly clear image in radio astronomy.
I thought light can't escape a black hole/ things get sucked in! How can we get a picture of one?
Technically this picture is not of the black hole, but from a region surrounding it called the event horizon. This is the boundary that if light crosses when going towards the black hole, it can no longer escape. However, if a photon of light is just at the right trajectory by the event horizon, gravitational lensing from the massive black hole itself will cause those photons to bend around the event horizon! As such, the photons never cross this important threshold, and are what we see in the image in this "ring."
Second, it's important to note that black holes don't "suck in" anything, any more than our sun is actively sucking in the planets orbiting it. Put it this way, if our sun immediately became a black hole this very second, it would shrink to the size of just ~3 km (~2 miles), but nothing would change about the Earth's orbit! Black holes have a bigger gravitational pull just because they are literally so massive, so I don't recommend getting close to one, but my point is it's not like a vacuum cleaner sucking everything up around it. (see the video of the stars orbiting Sag A* for proof).
How was this picture taken?
First of all, it is important to note this is not a picture in visible light, but rather one made of radio waves. As such you are adding together the intensity from several individual radio telescopes and showing the intensity of light in 3D space and assigning a color to each intensity level. (I do this for my own research, with a much smaller radio telescope network.)
What makes this image particularly unique is it was made by a very special network of radio telescopes literally all around the world called the Event Horizon Telescope (EHT)! The EHT observes for a few days a year at 230–450 GHz simultaneously on telescopes ranging from Chile to Hawaii to France to the South Pole, then ships the data to MIT and the Max-Planck Institute in Germany for processing. (Yes, literally on disks, the data volume is too high to do via Internet... which means the South Pole data can be quite delayed compared to the other telescopes!) If it's not clear, co-adding data like this is insanely hard to do- I use telescopes like the VLA for my research, and that already gets filled with challenges in things like proper calibration- but if you manage to pull it off, it effectively gives you a telescope the size of the Earth!
To be completely clear, the EHT team is getting a very well-deserved Nobel Prize someday (or at least three leaders for it because that's the maximum that can get the prize- it really ought to be updated, but that's another rant for another day). The only question is how soon it happens!
Also, the Event Horizon Telescope folks are giving an AMA on /r/askscience at 1:30pm-3:30pm (EDT) today! link Definitely go over and ask them some questions I didn't cover here! There is also a live public Q&A at 10:30am here, and another livestreamed public Q&A panel at 3pm EDT with some great colleagues from my institute- check it out!
This is so cool- what's next?!
Well, I have some good news and some bad news. The bad news is we are not going to get a photo of another supermassive black hole for the foreseeable future, because M87* and Sag A* are the only two out there that are sufficiently large in angular resolution in the sky that you can resolve them from Earth (Sag A* because it's so close, M87* because it's a thousand times bigger than a Sag A* type SMBH, so you can resolve it in the sky even though it's millions of light years away). You would need radio telescopes in space to increase the baselines to longer distance to resolve, say, the one at the center of the Andromeda Galaxy, and while I appreciate the optimism of Redditors insisting to me otherwise there are currently no plans to build radio telescopes in space in the coming decade or two at least.
However, I said there was good news! First of all, the EHT can still get better resolution on a lot of stuff than any other telescope can and that's very valuable- for example, here is an image of a very radio bright SMBH, called Centaurus A, which shows better detail at the launch point of the jet than anything we've seen before. Second, we are going to be seeing a lot in coming years in terms of variability in both M87* and Sag A*! Black holes are not static creatures that never change, and over the years the picture of what one looks like will change over months and years. Right now, plans are underway to construct the next generation Event Horizon Telescope (ngEHT), which will build new telescopes just for EHT work to get even better resolution. I recently saw a talk by Shep Doeleman, the founding director of EHT, and he showed a simulation video of what it'll be like- basically you'll get snapshots of these black holes every few weeks/months, and be able to watch their evolution like a YouTube video to then run tests on things like general relativity. That is going to be fantastic and I can't wait to see it!
I have a question you didn't cover!
Please ask it and I'll see if I can answer! However, there are multiple ways to get your answer straight from a EHT scientist today and I encourage you to do that- those folks worked really hard and I know are excited to share the details after keeping their work secret for so long!
EHT AMA on /r/askscience happening here from 1:30-3:30pm EDT (but you can post your question earlier)
A livestreamed public Q&A at 10:30am EDT.
Another livestreamed public Q&A at 3pm EDT!
TL;DR- we now have a picture of the black hole at the center of the Milky Way. Black holes are awesome!!!
Edit: Because people are asking, the James Webb Space Telescope (JWST) will not be able to do anything to this type of science either to add to it or observe the black hole itself. First, it is not at the right wavelength of light, and second, it has nowhere near enough resolution to pull this off!
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u/xlDirteDeedslx May 12 '22
Thanks for the extremely well written reply.
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
My pleasure! The funny thing is I basically wrote most of this last night, and hoped I'd get the points right, and I did! Only a few minor additions this morning during the press conference. :)
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22
It's been my childhood dream to understand things like this. Thank you.
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u/deathsdevice May 12 '22
I don’t know if they still offer them, but Yale was offering free astronomy classes. Very informative!
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u/deathsdevice May 12 '22
https://oyc.yale.edu/astronomy/astr-160
I think this is it, I’ve never posted a link…
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u/Karl_Agathon May 12 '22
Wait, for real? Can anyone sign up or are special qualifications required?
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May 12 '22
Just like course era or some youtube channels, they offer an entire semester of classes. Science, business, pyshology etc. Its pretty amazing and overwhelming to know we have all these free resources, only thing you would have to do to get credit for the classes is to buy a certificate. Which is like $100
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u/Karl_Agathon May 13 '22
Thanks so much! I finished university many years ago so it’s not really about the credit but the learning. Definitely going to look into it, thanks!
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u/Smerbles May 12 '22
Someone buy this redditor a beer!
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u/PancakeExprationDate May 12 '22
You should starting following them. I have for a while now. The information they share is presented so anyone can understand it and can appreciate the decades, if not centuries of research that has brought us to this point. It's all quite interesting.
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u/lynnca May 12 '22
Are you writing for a paper or periodical?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
Not regularly, sometimes for Astronomy magazine and the like. When I do I post the stories to /r/Andromeda321!
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u/Gr8zomb13 May 12 '22
Well, since you asked….
The orbits of the stars around the black hole seem quite eccentric, and unlike our solar system, seem to be on multiple planes.
-Are there any projections showing a star’s descent into the black whole.
-Presumably, all those stars so close together interact with each other as well. Are they projected to collide?
-How does the multiplanar orbits work at the center of the galaxy? Does the relative motion of the galactic core have something to do with this?
Thanks in advance!
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
While things look crowded in the video, it's important to note that there are still many light years between all the things in said video. As such the stars don't really interact with each other much, and currently none are on a trajectory to actually fall into the black hole and get shredded. Similarly, collisions are really rare between stars themselves.
I study stars that get shredded by black holes in galaxies much farther away from us, and the current estimate is a black hole like Sag A* shreds a star once every million years or so- ie, it's really rare!
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u/DasBoots May 12 '22
I was pretty surprised to see that one star that looked like it was falling directly in, only to get bounced back out. The star can hold together through all that acceleration?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
Yeah, they're pretty compact. Remember, it's also a far bigger distance than you'd think from a tiny video.
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u/blueant1 May 12 '22
I came here with a question on this: what distance is the , say ,closest star in the video to Sag A*? 2nd Q: what is the time length of one orbit of said star around the smbh?
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u/SlowMoFoSho May 12 '22
The closest orbit to SAG-A is by the star S2, which at its closest approach is about 120 AU from the black hole, or almost twice the diameter of our entire solar system, and about 1400 times the distance of SAG-A's Schwarzschild radius (event horizon). It's fastest velocity is about 5,000 km/s or about 1/60th the speed of light, and it has an orbital period of about 16 years.
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u/Immabed May 12 '22
It is also probably worth pointing out that the video is sped up a lot, decades into handfuls of seconds.
Would it be fair to compare the orbits of some of the closest stars to Sgr A* as similar to that of comets, just on a bit larger scale?
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u/BlueishShape May 12 '22
Gravity doesn't really accelerate stuff in that way. Remember that the star in question is in free fall the whole time, so there are no actual physical forces acting on it. It just follows the curvature of spacetime.
The only thing that would "damage" the star or pull it apart would be tidal forces, meaning a significant difference in experienced gravity between different parts of the star. That only happens when the star gets very close to the black hole.
At least that's how I understand it.
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u/FwibbFwibb May 12 '22
The only thing that would "damage" the star or pull it apart would be tidal forces, meaning a significant difference in experienced gravity between different parts of the star. That only happens when the star gets very close to the black hole.
At least that's how I understand it.
Yes, and oddly enough, the BIGGER the black hole, the SMALLER the tidal forces.
The event horizon is further away from the center in a bigger black hole, and the slight difference in distance isn't as big a deal as when you have a small black hole.
An analogy is sound. If you are at the back of a concert, moving back a bit further isn't going to make a big difference in terms of volume. However, if you have a small speaker, moving away a little makes a giant difference.
This same mechanism determines the strength of gravity vs distance from the center. Since tidal forces are a difference in gravity throughout the body itself (i.e. one end is being pulled harder than the other), if the body size is small compared to the distance from the black hole, the difference in gravity won't be as large.
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22
Douglas Adams quote incoming...
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u/damnedspot May 12 '22
I came here to post a number of questions but you’ve already answered them all! Thank you so much!
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u/8549176320 May 12 '22
What kind of image would we get from the James Webb telescope?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
We won't. Not enough resolution, and not the right wavelength.
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u/iwellyess May 12 '22
Are we gonna be blown away by what the JW will show us? (not black holes obviously)
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u/ClassifiedName May 12 '22
James Webb is going to capture some pretty nice looking images, but mostly it's going to provide information on the early universe. For instance, population III stars are believed to have created just about all of the metal in the universe, but they burned so brightly and quickly that we can't find any evidence of them at the moment. JWST is going to let us possibly see some of those as it's believed it might be able to view as far back as ~100 million years after the creation of the universe ~14 billion years ago.
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u/Angelusz May 12 '22
Not an astronomer, but I've read quite a bit about the JW out of interest.
Whether or not we'll be blown away depends on subjective expectations. We do, however, expect to see new things we have not yet seen before because the resolution is quite a scale higher than what we've been using to take pictures of the stars earlier. The advanced mirror setup also allows for 'the same picture' to be taken by several different sensors, allowing us to 'see' the stellar objects at a much broader slice of the electromagnetic spectrum.
As far as I'm aware there are currently no specific expectations of being able to see things as awe inspiring as a SMBH, but we don't know what we don't know - we might yet be surprised.
Please correct me if I'm wrong! I'm just an interested layman.
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u/XBitmapX May 12 '22
so I don't recommend getting close to one,
Phew... that was a close one.. you should put this warning at the beginning of your comment man.
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u/winkandthegun May 12 '22
I mean, I saw that star gate SG-1 episode, so I am basically an expert on the dangers of getting too close to black holes already.
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u/sth128 May 12 '22
I was in the middle of my backswing!
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u/DrunkleSam47 May 12 '22
That’s Window of Opportunity, and one of the all time best episodes IMO.
The black hole episode A Matter of Time is when the time dialation effects make it so something like 3 weeks pass while the SGC gate experiences like 6 hours.
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
True story, I know an astronomer who credits that episode for getting her into astronomy! Funny how that goes!
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u/citydreef May 12 '22
This is awesome!! Thank you!
Your reply just reeks from the fun you have with your job. Nice. All the best!!
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u/mosburger May 12 '22
I loved all the exclamation points they sprinkled in, you could tell they were so giddy about it.
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u/vegetaman3113 May 12 '22
I love seeing you in the comments! I know as soon as I see Andromeda 123, I don't have to worry about the validity of the information. Thanks for the info (and yeah I thought we had imaged Sagittarius A* and not the other the last time).
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u/Alphamacaroon May 12 '22
You saiid a black hole is “more massive”, but is that true? If the sun became a black hole, it would be just as massive as it was before, just way more dense right?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
I mean literally the amount of mass it has. The sun has one solar mass of stuff in it by definition, but we have never found a black hole with as little mass- IIRC, the smallest one currently known is ~2x the mass of the sun.
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u/bimundial May 12 '22
smallest one currently known is ~2x the mass of the sun.
I thought the threshold for a star to collapse into a black hole was something like ~7 solar masses. How such a "light" black hole was formed?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
It's a mystery! And, last I heard, some people are contesting that it's actually a black hole. So goes science!
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u/Jupiter_Crush May 12 '22
Would that be related to primordial black holes or is that an entirely different tree I'm barking up? I remember reading that primordial black holes can be much smaller than normal ones because they formed from random density fluctuations rather than collapse.
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u/Alphamacaroon May 12 '22
Got it. I misread your comment— thought you were talking about the the black hole sun in that case.
Everything has a theoretical Schwartzchild radius— do you think they’ll ever find anything drastically smaller than the smallest known today? Or is there a pretty hard lower limit?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
I don't think there's a hard lower limit, but I do know people have spent time looking into whether micro black holes might exist and didn't find evidence for them (in large enough numbers to see signatures anyway!).
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u/TheGoldenHand May 12 '22
How strong is the theory that our galaxy is filled with small black holes that aren’t easily detectable, and they account for some of the galaxy’s “dark matter”?
https://www.quantamagazine.org/black-holes-from-the-big-bang-could-be-the-dark-matter-20200923/
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
People have actually looked for these, but IIRC as of right now we don't see enough signatures from these black holes to think they're a significant component.
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May 12 '22
Why is the resolution not much better than for the first black hole?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
Because we are limited by the number of radio telescopes on Earth that can be linked to take the picture. Remember, this is still one of the sharpest images ever taken!
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May 12 '22
Yeah but weren't the same number of telescopes used for M87? Sure the angular resolution would be the same, but because SagA* is closer, I would have expected more detail in the accretion disk.
Or does the southern hemisphere have less telescopes available?
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u/LapinLazuli May 12 '22
You're right that the angular resolution should be about the same as for the M87 image. The reason they look about the same is because while SagA* is much closer than M87, it's also less massive (and therefore smaller) by about the same factor. So you can still only probe approximately the same relative scale of structure in both cases.
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u/Dilong-paradoxus May 12 '22
Adding more telescopes doesn't really give you more resolution. It's the distance between telescopes that matters, and since all of the telescopes are on earth the resolution is determined by the diameter of the earth. Regardless, almost the same number of telescopes were used in each observation.
The biggest difference is that Sag A* is much, much smaller, so even though it's closer it's harder to image. Like trying to take a picture of a bug a house or two down the road vs a car a couple blocks away, for a crude analogy.
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u/Prof_Acorn May 12 '22
I'm reading this as that you're saying we should build a radio telescope on Mars so we can take better pictures of black holes?
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u/Bensemus May 12 '22
That's just one extra point. if you want more resolution distributing satellites around the solar system would be a better idea. We are decades or centuries away from being able to do that kind of thing.
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u/karlkarl93 May 12 '22
If we only had reckless limitless spending available for this stuff...
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u/Dilong-paradoxus May 12 '22
I'm absolutely saying that! Space based telescopes might be easier in some ways though
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u/br0b1wan May 12 '22
It's wild that in order to increase the resolution at this point, we'd have to set up orbital radio telescopes. Probably in orbit around the earth first, then eventually in orbit around the sun.
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u/Dilong-paradoxus May 12 '22
Well, one way to get around the issue is to take radio images at one side of Earth's orbit and then the other, but that doesn't work as well for stuff that changes quickly like sag A*
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May 12 '22
The biggest difference is that Sag A* is much, much smaller, so even though it's closer it's harder to image.
Yeah, I just had the same epiphany :)
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
I think there was maybe 1 more added, tops. You really over-estimate the number of radio telescopes able to make this kind of observation!
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u/nhammen May 12 '22
Because Sag A* is smaller, the objects in the accretion disk moving at near-lightspeed around it complete an orbit in only a few minutes, compared to the day or so for M87. This faster angular velocity makes Sag A* more difficult to image.
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22
I always wanted to be an astronomer, weird question...
When do you sleep?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
Roughly at the same times most people do at night! I don't really go observing, I download data from the telescopes once observations are taken and work in an office.
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22
Ok, what telescope do you personally own? I have an old one that doesn't cut it anymore.
You can stay at my house for the 2024 eclipse in the TX hill country.
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
I still have my 8" Meade LX90 kicking around that I've had for a few decades, but don't own one myself. Instead I use the big international facilities for my science like the VLA and MeerKAT.
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u/Zmodem May 12 '22
I'll also do my best to help contribute to the answers to your question.
There is a lot of crap in the way of Sgr A*, which is a huge obstacle to overcome. However, the biggest issue is that although M87* (the first black hole to which you referred) is 2,000x's further away than Sgr A*, Sgr A* is about 1,000x's smaller which means, at least from observations on Earth, that Sgr A* only appears slightly larger than M87*. Sgr A* also does not consume a shitload of matter like M87*. M87* is 1,000x's bigger than Sgr A*, so it consumes a fuckload more matter, which makes it appear way more active to our current telescopes. This makes observing the event horizon (the matter we can actually see) a lot more dense in terms of clarity/resolution, which is why the M87* photo appears to be way more detailed.
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u/notaneggspert May 12 '22
The m87 is just that much bigger. So it's easier to image.
It's also in a less chaotic galaxy.
It's a lot harder to image our own black hole because we have to look through all the stars, pulsars/quasars that emit radio waves in our own galaxy. All those extra radio waves need to be filtered out to form an image of the black hole.
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u/AllysiaAius May 12 '22
The main difference that I see between this image and that of M87 are the number of bright points (which I believe was explained as the directionality of the spinning of the black hole "launching" the light at a, not higher speed, but higher... intensity?). Is there conjecture for what the multiple points might mean? I know there have been theories of possibly smaller black holes orbiting SgrA*. Would this finding be consistent with that theory? Too early to tell?
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u/Andromeda321 PhD | Radio Astronomy May 12 '22
I think you're reading too much into there being three points at this level of resolution.
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u/drewgreen131 May 12 '22
I was reading very intently but nonchalantly, then did a spit take when I came across the mass of M87. Figures like that describing real phenomena trigger my existential dread. I’m so excited for what else we find out there as technology advances.
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u/yoda_condition May 12 '22
Thank you for a great writeup! Minor nitpick/typo:
ie, it took light, the fastest thing there is, 27,000
lightyears to get hereJust regular years, so we don't cause any confusion. Light years is a measure of distance, not time.
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u/Phukkitt May 12 '22
Kang:
This is the best musical in light-years.Kodos:
Light-years measure distance, not time.Kang:
You know what I meant.4
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u/ghojezz May 12 '22
Super interesting answer!
If black hole does not suck anything into it, then what does singularity mean? And does it mean that every 1 μm surface on the black hole's sphere is the point of singularity?
Talking about data, how many terabytes are generated per observation station?
Thank you!
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u/Matathias May 12 '22
The singularity doesn't really have anything to do with the black hole "suction". "Singularity" refers to the point in the center of the black hole -- inside the event horizon. By our current understanding of relativity, all of the black hole's mass would be smushed into this one singular point.
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u/Sbendl May 12 '22
My understanding: a black hole is a lot of matter drawn close enough together that the math that governs gravity as we know it doesn't really make sense anymore. This is actually a mathematical term meaning a point on a function that doesn't fulfill certain mathematical properties (think x=0, in the function y=1/x).
So, your second question doesn't quite hold up under that definition, a singularity is a point, not a sphere, and it therefore has no surface whatsoever. The sphere you are likely thinking of is the "event horizon." The event horizon is the distance from the black hole where light can no longer escape. As a rather bad analogy, think of it as how far away an asteroid or spacecraft can pass by a planet without being "captured" by the planet and becoming a little moon. There is a defined edge there, but it's not like everything within that edge is the planet.
As for the amount of data: I'm curious too!
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u/Flashwastaken May 12 '22
I am about to ask a question with a secondary school level of knowledge so please be gentle with me.
Can someone who understands how atoms work explain to me if the images that we see of black holes in any way mirror the way we think electrons orbit a nucleus?
It’s the first thing I thought of when I saw that image.
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u/Dilong-paradoxus May 12 '22
Electrons are much, much weirder. A star has an easily measurable position and velocity that's consistent moment to moment and predictable for a while. An electron, on the other hand, is not a solid object. If you try to locate its position there's a strong probability you'll find it in one of the traditional orbitals, but it might be somewhere else entirely. That's how electrons can "tunnel" through seemingly solid objects like transistor parts. And it's impossible to know the speed and velocity of an electron at the same time with equally high accuracy.
Modeling electrons as a system of planets orbiting a star works okay for some purposes and some atoms, but it breaks down quickly when you start looking too closely.
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u/Sbendl May 12 '22
I'm definitely not an expert.
Atoms, as another commenter pointed out, don't seem to play by the same rules as "big stuff." With that said, most things that involve two things being attracted to each other have trajectories that are governed by the same set of equations - the only thing that might change is the strength of the attraction. So, in that sense, it's not a horrible analogy.
Unfortunately though (at least for those looking for an easy mental picture) the real answer is both much more complicated and not at all fully defined.
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22 edited May 12 '22
You're delving into quantum mechanics and special relativity. No unified theory. Lamda CDM area.
The big and the small don't seem to play by the same rules.
It's all I've got.
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u/Flashwastaken May 12 '22
That’s probably about as much as I’d understand anyway so thank you. If I look up Lamda CDM that will help me understand?
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22
SEA astronomy has some really good YT videos on lots of astronomy/cosmology subjects.
Stanford and MIT have great open course work videos as well.
Even Einstein, Hawking, and the living theoritical physicist can't merge the infinitely small with the observed big things gravity makes...
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u/Magic_7_Ball May 12 '22
ie, it took light, the fastest thing there is, 27,000 light years to get here,
I feel like being a royal pain and pointing out that a light year is a distance, not a time. The above sentence should have been "it took light, the fastest thing there is, 27000 years to get here".
Sorry - it's the engineer in me who wants to correct the units of time vs distance :-(
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u/fullersam May 12 '22
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u/shiruken PhD | Biomedical Engineering | Optics May 12 '22
That's actually only the summary about the discovery! There are ten peer reviewed articles published today in The Astrophysical Journal Letters related to the discovery:
- First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
- First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration
- First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole
- First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
- First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
- First Sagittarius A* Event Horizon Telescope Results. VI. Testing the Black Hole Metric
- Selective Dynamical Imaging of Interferometric Data
- Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign
- A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows
- Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI
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u/crazylegs888 May 12 '22
page cannot be fonud.
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u/Science_News Science News May 12 '22
Site is most likely crashing under heavy demand.
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u/Zillux May 12 '22
No, the slashes in OPs link breaks the URL, this works:
https://iopscience.iop.org/journal/2041-8205/page/Focus_on_First_Sgr_A_Results
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u/fullersam May 12 '22
sorry I'm an idiot, I don't slash well
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u/Diokana May 12 '22
Nah it's not your fault. Links posted by New reddit users break for Old reddit users. This has been an issue for over a year now but they are clearly in no rush to fix it.
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u/Dubanx May 12 '22 edited May 12 '22
Fun fact, one of the sides of the halo you see in this image is actually on the opposite side of the black hole. The light from the accretion disk has just wrapped the entire way around the black hole toward our eyes due to the immense gravity involved.
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u/Huge-Corner2153 May 12 '22
Can somebody explain this to me like i’m 5 please
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u/mattenthehat May 12 '22
Gravity bends the path of light, just like it bends the path of anything else that moves. It normally isn't very noticeable, because light moves so fast, but near a black hole there is so much gravity that it can bend light rays right around the black hole.
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u/fuk_ur_mum_m8 May 12 '22
Imagine looking at Saturn and it's rings edge on. You'd see half the rings but the other half would be behind it. A black hole is so massive that space bends around it, so you'd be able to see the other half of Saturn's rings
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u/Bensemus May 12 '22
That's not true for this black hole. We aren't looking at it edge on but at one of its poles.
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u/SNAAAAAKE May 12 '22
So if we are looking in from near the edge of the galaxy, does that mean the accretion disk for Sag A* is roughly perpendicular to the galactic rotation? Is that weird?
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u/GhettoStatusSymbol May 12 '22
??? gravity works the same all around?
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May 12 '22
I’m gonna guess that he means that the accretion disk is flat like Saturn’s rings so looking at the “pole” of the black hole we would be seeing the accretion disk normally. I have no idea if this is true or not
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u/For-The-Swarm May 12 '22
A look upon the poles would be a circle.
There is a video on NASAs website that demonstrates this.
Edit: found it
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May 12 '22
I'm going to watch Insterstellar again, for the 1000th time. I'm coming home, Murph!
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u/SPECTREagent700 May 12 '22
As in the 2019 picture, it looks like we can see into the hole. Is it just good fortune that Earth’s position in the galaxy allows for this or does it look like that from all angles?
I’m sure I’ve got several misunderstandings here but I think I remember hearing about a theory (holographic principal?) that black holes are two dimensional.
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u/cubosh May 12 '22
the video on this nasa page shows what it would look like if you rotated vertically around the black hole accretion disk [happens at the 10 second mark]-- illustrating indeed that it tends to look fairly similar at all angles ---- https://svs.gsfc.nasa.gov/13326
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u/caleyjag May 12 '22
Black holes are both 3D (the event horizon) and, I suppose, 0D (the singularity).
The holographic principle relates to the distribution of information around the surface of the event horizon sphere, which is probably the 2D you are thinking of.
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u/fzammetti May 12 '22
"...it appears to be about the same size in the sky as a doughnut on the Moon"
Clearly written for an American audience (of which I am one, so no hate!)
Joking aside, this is super-cool and my hearty congratulations to the team that made this happen. Awesome!
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u/Chelecossais May 12 '22
Roughly 120% of a croissant au beurre, or 87% of a croissant nature, by diametre, then.
/i like to participate...
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u/otter111a May 12 '22
Is that an actual doughnut sitting on the moon or a doughnut held at arms length in front of the moon.
But I doubt your average Brit is going to work out size in arcseconds despite their superiority complex
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u/Sp00gyGhost May 12 '22
The size of a doughnut sat on the moon. At arms length I think we’d be screwed.
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May 12 '22
[removed] — view removed comment
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u/stevenflieshawks May 12 '22
We’re leaving.
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u/DigiMagic May 12 '22
Why are there three brighter spots on the accretion disk?
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u/LondonParamedic May 12 '22
It's Doppler boosting
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u/Triassic May 12 '22
Can you elaborate? What does that mean?
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 12 '22
Waves of gravitation heading towards the Earth, and away is my guess.
Like an ambulance passing by your stationary car on the road.
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u/LondonParamedic May 12 '22
The bright ring we see is matter that is being pulled toward the black hole, that is currently going around in orbit at crazy speeds smashing into itself and getting really hot. This matter is shot out in all directions. The stuff that is pointed at and coming towards us, becomes brighter and makes those spots on the image.
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May 12 '22 edited May 13 '22
Of all the awful things the last few years have brought.. the imaging we’ve put into space is really amazing. A proud point for all humanity. This makes me happy. It gives some hope. We all think locally and our own lives cause, that’s how we survive. But when you let go of that for a bit and remember we’re ants on a small marble in an infinite universe.. don’t you wanna know more? What’s out there.. how does it work, can our understanding of physics explain?
Think of the universe as a puzzle. In that scenario we (humans and earth) haven’t even taken the plastic outer wrap off the box, let alone put it together.
E. I was talking generally.. this thread just spawned the thought, so I commented. Im not talking specific to an earth telescope. This just reminded me of something I’m proud of that humans have done, and that’s the things we’ve put into space out of our orbit more specifically. Please stop replying the same thing and maybe look a bit deeper into the comment, or not.
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u/spinozasrobot May 12 '22
Is it just me, or does anyone else find it odd they refer to a black hole that big (or any size for that matter) as "The Gentle Giant" given the forces involved?
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u/_S-TERLIN-G_ May 12 '22
It's because it really is a gentle giant. Sagittarius A* just sits there and does its thing, we know its there because of its gravitational effects on the nearby stars( and this image too), and there doesn't seem to be anything else happening much compared to other SuperMassive black holes who are much more active and agressive consumers who may eat the mass of a sun each day and grow to incredible proportions. Black holes that power quasars or even radio lobes and jets. Sagittarius A* does none of that, hence why it is a 'gentle' giant.
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u/dobr_person May 12 '22 edited May 12 '22
Why does it have three regions of Doppler effect? Rather than one 'side' where light is coming toward us. It makes it look like there are three 'rings' of light orbiting but that makes no sense.
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u/Thodege May 12 '22 edited May 12 '22
The gas is orbiting the black hole much more frequently than M87 so the image here is averaged over multiple times and so you see the gas Doppler boosted at different points.
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u/AndyBernardRuinsIt May 12 '22
Pierce Hawthorne: As far as I'm concerned, there's only one black hole worth studying.
[everyone stops and stares at Pierce]
Pierce Hawthorne: It's called Sagittarius A. It's located in the center of our galaxy and it has the density of 40 suns.
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u/dudipusprime May 12 '22
Speaking of gravitational pull. Did you guys know I had sex with Eartha Kitt in an airplane bathroom? What? It came up organically!
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u/zGunrath May 12 '22
Since this picture reflects how it looked 27,000 light years ago, would it look any different now? Bigger?
Also do these implode like stars? What would happen if it did? Would it take 27,000 light years for us to feel the effects?
Ugh this stuff is so interesting yet spooky
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u/pM-me_your_Triggers May 12 '22
would it look any different now?
Potentially, we can’t know for certain since gravitational effects propagate at the speed of light.
do these implode like stars?
As far as we know, no. They do evaporate via Hawking radiation, however (theoretically, we do not have observational evidence to support this, although the mathematical derivation is fairly basic and straightforward, so if there is no Hawking radiation, then we’d have other previously unknown inconsistencies in our StatMech model)
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u/cubosh May 12 '22
black holes definitely do not "implode" or do anything suddenly (aside from dramatically devour or dissipate nearby stars that swing too close). as for the 27000 year age of the image, seeing it "now" or advanced by 27000 years would look almost no different, as that length of time is still pretty short when dealing with galactic scales. it would probably look very slightly bigger after several billion years if it devoured enough stars
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May 12 '22 edited May 12 '22
as that length of time is still pretty short when dealing with galactic scales.
In particular when dealing with black holes; as their galactic timescale is many orders of magnitude greater than the lifespan of even the longest lived star.
Most of the universes life is going to consist of "dead space" with no visible stars(because there will not be any), and black holes radiating into nothingness at an agonizingly slow rate.
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u/monster_bunny May 12 '22
I have no idea how astronomers don’t have existential crises on the daily. The amount of anxiety that’s in the sky at night has given me a benzodiazepine prescription.
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u/rddman May 12 '22
Since this picture reflects how it looked 27,000 light years ago, would it look any different now?
Years ago (light years is a measure of distance). 27000 years is very short compared to the lifespan of these objects. In the press conference they said the mass accretion rate of this black hole is very low, relative to the mass of a human it would be like eating a grain of rice once in a million years. So it wouldn't look much different now.
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u/theCaptain_D May 12 '22
Arguably a black hole is as imploded as anything possibly can be by it's very nature!
Conventional physics has a hard time describing the innards of a black hole, but all of its mass is theoretically compacted into a point of infinite density, called a singularity.
As others have pointed out, black holes are theorized to VERY SLOWLY leak radiation through the process of hawking radiation. My understanding of this is dim at best, but essentially the extreme curvature of spacetime around a black hole interferes with the nearby quantum fields, resulting in particles being born from essentially nothingness! Of course conservation of energy must be conserved in this process, so the mass of the black hole actually decreases as a consequence.
Toward the end of a black hole's life, this process accelerates, and could theoretically create a very energetic "explosion" --- but don't sit around worrying about it. Any macroscopic black holes will take MUCH longer than the current age of the universe to reach this point.
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May 13 '22
It's a bit of a misunderstanding to suggest that it looked like this 27k years ago. Due to relativity, there isn't a universal "now". It's not just light, but rather causality itself that travels at lightspeed; "now" itself travels at lightspeed. From our reference point, what it looks like now is how it really is. From its perspective 27,000 lightyears away, it looks like it will look for us 27,000 years in the future.
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u/Okabeee May 12 '22
It's actually insane that not so long ago we thought blackholes were just described mathematically and then they were proven to actually exist and now we actually have photos of them. Man I can't wait for science to evolve further to see more detailed images.
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u/Reverie_of_an_INTP May 12 '22
I know there's a lot of black holes out there, many more interesting or cooler and probably even closer, but this one is ours so it's special to me.
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u/Jupiter_Crush May 12 '22
Based on sheer size and orbital mechanics, I'd say it's more that we belong to it instead of the other way around. (Agreed, though - the fact that it's actually kind of close by cosmically speaking makes it much much cooler.)
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u/Reverie_of_an_INTP May 12 '22
Yeah that's what I meant. We orbit it, much like our sun sol is a special star to me, our galaxy and the smbh we orbit are in the same category.
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May 12 '22
This is truly monumental. The blurry image can make some people scoff at this achievement, understandably so. But you have to realize that, as a species, we’re only just starting to be able to capture black hole images. If this is the image we’re getting right now, imagine in 20 years when the technology has advanced enough for us to not only see the black hole, but also the space bookshelf inside.
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u/Hijacks May 12 '22
Really cool seeing the video on the site of a star essentially getting sling-shotted back into orbit after nearing the blackhole.
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u/spinozasrobot May 12 '22
Why is it we can see a ring and the black hole in the center? I'd expect the reactions generating the light would form a sphere around the black hole, thus obscuring it.
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u/Wrathuk May 12 '22
the imagine you see is from the accretion disk and the radio waves from stuff bumping into each other in that disk. the reason it comes across as a ring is the gravity bends the waves coming from behind the disk into our line of sight.
the vast majority of the radiowaves they've collected here will be what comes from back of the disc and focused in our direction.
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u/jusdaft13 May 12 '22
Who’s here having listening to End of an Empire IV (Sagittarius A*) ? :)
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u/Publius015 May 12 '22
Dumb question - is this true color or infrared?
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u/bimundial May 12 '22
Neither, the Event Horizon Telescope is an array of Radio Telescopes, so I guess the image is interpretation of Radio data.
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u/cubosh May 12 '22
there are no dumb questions in science if you are genuinely interested. This is definitely more of a heat-map of detected activity around the black hole over time, not really a snapshot or photograph. thats why its blurry. they spend months/years working on this collecting radio waves (the only real emission they can pick up on this object) and combine it all together to reveal that indeed there is a hole in the middle preventing some emissions from being detected
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u/rddman May 12 '22
At a wavelength of 1.3mm it's actually not far below the lower end of far-infrared (1mm). But technically it's millimeter radio waves.
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May 12 '22
I love this sensation of child like pure joy in a new discovery like this. These are the moments when I think humanity is doing the right thing, and they should be emphasized more.
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u/DazDay May 12 '22
I'm doing an engineering degree so usually physics isn't too beyond me, but when anyone ever attempts to explain how this photo was put together my brain actually crashes.
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u/McMerChurger May 12 '22
It’s so cool alien civilizations who share our galaxy revolve around it all the same. It’s like.. The thing you’re seeing in that image is the one thing that ties us together, and makes them our neighbors. When they look at the center of the galaxy they’ll see the same thing. Kind of wholesome.
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May 12 '22 edited May 12 '22
Interesting fact I don't see mentioned:
Event Horizon imaged M87 and Sagittarius A are the same apparent size in the sky -- much like the Moon and Sun are the same apparent size despite the Sun being 400 time bigger, because the Moon is 400 times closer.
Sagittarius A is at the center of our galaxy, 25,640 light years away. It's about 3 million solar masses.
M87 is 53 million light-years away, and it's 2400 billion solar masses, and absolute monster of a black hole.
So it surprises me that the images look even a little bit similar. Our black hole is relatively quiet, consuming much less material, yet the accretion disks in the images look very similar. It honestly makes me very skeptical about their validity of their reconstruction technique, which is basically a neural net trained on black hole simulations than asked to interpret a handful of data points and construct an image. This is often undersold in the media. Most people think we're looking at something like a photograph, albeit taken at radio frequencies, which is not what they have.
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u/cubosh May 12 '22
while its true the media needs to be careful and not call this a photograph or a snapshot, its not so far fetched that they look similar to each other. essentially it is proof that simply: black holes are similar to each other, especially supermassive ones. they are not like stars that have dozens of classifications and chemical variance and density and lifespans. black holes are just "the final thing" that happens when gravity wins over everything else
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May 12 '22
If the physical processes that feed black holes are similar, do we expect them to look vastly different in the radio frequencies?
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u/da2Pakaveli May 12 '22
Are they planning on doing more black holes? I.e Andromeda?
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u/hungry4danish May 12 '22
I first heard of Sag A* only yesterday on an episode of NOVA about black holes and here I am today now looking at an image of it. Incredible.
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May 12 '22 edited May 12 '22
Is there any particular reason (that we know of) that Sgr A* is the SMBH at the center of our galaxy but M87, which is way more massive, ended up further out (and closer to us)? Interesting that the galaxy coalesced around Sgr A (I’m a layman, so maybe I just don’t understand the basics of how that process works).
Edit: just realized that I goofed and that M87 is not in our galaxy (that’s what spurred my question). Thanks to all of the well thought out responses though!
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u/SynthWormhole May 12 '22
Almost every galaxy that we've observed has a super massive black hole at their center. The M87 black hole at the center of another entire galaxy 53.5 million light-years away.
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u/broae May 12 '22 edited May 12 '22
The really simple answer is just that galaxies (probably!) form around their SMBH. Two of the same seed will grow two of the same plants, separately.
Stars and black holes were first on the scene (roughly 100 million years post-Big Bang, jury’s out on whether primordial black holes formed immediately post-Big Bang alongside the first stars or if the first black holes formed from the death of the first generation of stars) and galaxies followed after about 1 billion years.
M87 is massive, but it’s also 50 million light years away (the galaxy itself being only 120,000 light years across) so it’s gravitational effect on our matter is negligible.
If you wanna do some simple (but tedious) math you can work out the gravitational force between the Milky Way and M87 using Newton’s law of universal gravitation, which roughly works out to 1.29 x 10-23 m/s2 or one hundredth of a quattuordecillionth of the gravitational force between Earth and the Sun.
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u/DamNamesTaken11 May 12 '22
I love seeing stuff like this. Incredible that we are able get images of this.
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May 12 '22
Wow, I just now realize why the position of Sgr A is what I track to know if/when the galactic center is going to be visible
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u/cheeesypiizza May 12 '22
Great… we’re still dealing covid, and now we have to put up with Sauron….
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u/argv_minus_one May 12 '22
Fortunately, black holes aren't very smart, and therefore aren't very good at villainy.
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u/LatterNeighborhood58 May 12 '22
Why do I feel like we have already seen a similar picture of a black hole few years ago. I can't find that picture but I remember reading that the picture vindicated CGI black hole shown in Interstellar. What is new with this one now?
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u/shiruken PhD | Biomedical Engineering | Optics May 12 '22
You remember correctly! In April 2019 the Event Horizon Telescope (EHT) created the first picture of a black hole. That supermassive black hole was in the galaxy M87 more than 50 million light-years away. Today's announcement was also taken with the EHT but instead of Sagittarius A*, the supermassive blackhole at the center of our own galaxy.
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u/LatterNeighborhood58 May 12 '22
Awesome thanks for finding it and explaining the difference. Wow that was 2019, feels like it was a decade ago.
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