Q: why are galaxies like ours so good at golf?
A: there's usually a splendid hole in one.
Astronomers reveal first image of the black hole at the heart of our galaxy
131–140 of 329 posts
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#132No post body was provided.
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#133I find the whole thing amazing and captivating - yet the image is … huh … slightly underwhelming. It looks like some gaussian blurred random image. I wish it could be the kind of crisp image JWST ‘sent’. It’s difficult to force oneself to not romanticise these un-visible things based on artists visualisation we got accustomed to.
It's actually one of the sharpest images ever made - in terms of angular resolution. The Sag.A* ring is about 51 microarcseconds in diameter. The EHT has a theoretical resolution of ~25 micro arcseconds. For comparison NirCam on Webb has a pixel resolution of 70 miliarcseconds (about 2800 times worse resolution than EHT). The reason it looks blurry is that the black hole features are close to the resolution of EHT so…
Can someone do the math for me?
Let's say I'm 6 feet tall... what object would I have to hold out at arm's length, to have the same angular width as the entirety of this image?
A bacteria? A virus?
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#134I find the whole thing amazing and captivating - yet the image is … huh … slightly underwhelming. It looks like some gaussian blurred random image. I wish it could be the kind of crisp image JWST ‘sent’. It’s difficult to force oneself to not romanticise these un-visible things based on artists visualisation we got accustomed to.
There’s a good Video from Kip Thorne showing why the “real” images differ from the idealized one that made much fanfare in Interstellar
(Edit) to add that it’s about 22minutes in.
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#135Earlier quoted context omitted.
For a small-mass central black hole (CBH), the spin-spin coupling of the CBH and the bulk matter of a relatively small and sparse galaxy is so small that it the orientation of the spin axis is almost unconstrained. That from Earth we look down on the CBH's north pole (right-hand-rule: the bright features appear to circulate counter-clockwise, and there is decent evidence in them that the black hole's spin is in the s…
With all the copious computing power today and given this problem seems mostly non-quantum, do simulations bring any significant insight at all?
Yes, simulations are in heavy use in galaxy dynamics. Two (example) research groups: https://www.nao.ac.jp/en/research/project/cfca.html> https://pweb.cfa.harvard.edu/research/science-field/computat...>
and the most relevant wikipedia page https://en.wikipedia.org/wiki/Computational_astrophysics>.
Indeed today's event https://www.eso.org/public/news/eso2208-eht-mw/> involved many of the techniques mentioned on the pages above, with paper III (freshly un-embargoed, so I have not perused it) appears to be a good starting point if you feel technically inclined.
I'm not exactly sure what you mean by "non-quantum" -- in general making sense of extragalactic central black hole observables (and even obtaining them in the face of e.g. astronomical and atmospheric extinction) depends very sensitively on understanding various types of scattering (especially Compton and its inverse) and atomic electron transitions / (quantum-mechanical) spin-orbit interactions. This has to enter into matching the results of a simulation from data obtained by observatories.
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#136I am very skeptical of the Event Horizon Telescope (EHT) images because they are not following a scientific method that results in a true representative image of their target. In my opinion astronomy is jumping the shark with these images by making this a big PR stunt. I've looked at their methods for their earlier images and they seem to be hunting for a circle that looks like a black hole in their data. The EHT's f…
I share your skepticism.
To others: Before voting me down, please consider these arguments.
As I understand, this image is not from visible light, not a photo, more like plotting radio measurements. "black holes" are the brightest objects in the universe. It's a bit like an alien scientist showing an X-ray picture of a skeleton:"This is a human!" Some quotes from https://en.m.wikipedia.org/wiki/Black_hole :
"Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly."
The same article is full of words like "implies", " inferred", "indirect" etc. It's not directly proven black holes even exist, see Alternatives paragraph. I'm not sure it's physically possible to take a visible light picture of a "naked" event horizon - then black hole images are pure phantasy.
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#137Earlier quoted context omitted.
Why do you think you know more about astronomy than a team of scientists publishing peer reviewed information?
Peer reviewed has nothing to do with the scientific method. It is just a layer of scientific bureaucracy. Just give me a calibration image of another celestial body and I'll be happy.
You realize peer review isn't just something you do and they automatically publish you, right? Peer review makes sure your science is sound.
But I'm sure you're more of an expert than anybody serving in a peer review board.
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#138Earlier quoted context omitted.
With all the copious computing power today and given this problem seems mostly non-quantum, do simulations bring any significant insight at all?
Yes, simulations are in heavy use in galaxy dynamics. Two (example) research groups: https://www.nao.ac.jp/en/research/project/cfca.html > https://pweb.cfa.harvard.edu/research/science-field/computat... > and the most relevant wikipedia page https://en.wikipedia.org/wiki/Computational_astrophysics >. Indeed today's event https://www.eso.org/public/news/eso2208-eht-mw/ > involved many of the techniques mentioned on th…
Thank you for the pointers! By non-quantum I meant that to simulate the motions at that scale (including rotation) it seemed like you could go quite far just by using relativistic physics. But I guess there is not much ordinary about black holes so my mental model is likely quite a ways off.
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#139> “We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity," And ten thousand physicists sighed disappointingly.
Gravitational physicist here. Every time we look in a new place and see that GR still works, it is pretty amazing. Part of this is the fact that everyone in the field works very hard to find a crack in GR's armor, and so far it has resisted everyone. The other part is that GR has a romantic beauty to it, both in structure and in predictions. Each time GR matches reality in a new context, the feeling is akin to watchi…
I majored in physics, and at least half of the enjoyment is seeing how pure and beautiful the theory is, how it all works out somehow, while wiping tears away from your eyes at the library.
(That's counterbalanced with the tears shed over your midterm grades.)
Re: Astronomers reveal first image of the black hole at the heart of our galaxy
#140This image came out several years ago or I have seen the future.