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Astronomers reveal first image of the black hole at the heart of our galaxy

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Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#71

Post by bell-cot »

kloch wrote: post #57
mabbo wrote: post #52

Earlier quoted context omitted.

> The only way to get higher angular resolution is to use higher frequencies (which they are working on) or use radio telescopes in space to get longer baselines than the diameter of the Earth. Would it be possible to use the same trick in space? IE: get a baseline the diameter of Earth's orbit (roughly)?

For Interferometry to work the data from different baselines has to be collected at the same time so waiting 6 months does not help. Spacecraft could theoretically be used to extend the baselines but the volume of data to be transferred is prohibitive with current spacecraft comm tech. Even on Earth they resort to shipping cases of hard drives instead of transferring over the Internet. One technique where simply wait…

I wonder what sort of range/throughput you could get with "Heavy" versions of the inter-satellite communications lasers which SpaceX is putting on their Starlink satellites...

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#72

Post by jeffbee »

nuccy wrote: post #44
jrgd wrote: post #32

I 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.

Well, given that JWST has at least 2000 worse resolution that EHT (see my comment below on that topic with some links). Thus the blurriness of this observed object is just a result of enormously small size versus distance to it. Any star observed by JWST is much-much bigger (i.e. has bigger angular size). During the live event [1] they make a lot of size/distance comparisons, like resolving individual bubbles in a be…

Yeah, the thing about “supermassive” black hole is that it sounds terrifying in extent but it actually is not. The sun contains almost all of the mass of our solar system but the SMBHATCOTG contains essentially none of the mass of the galaxy.

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#73

Post by privong »

kloch wrote: post #57
mabbo wrote: post #52

Earlier quoted context omitted.

> The only way to get higher angular resolution is to use higher frequencies (which they are working on) or use radio telescopes in space to get longer baselines than the diameter of the Earth. Would it be possible to use the same trick in space? IE: get a baseline the diameter of Earth's orbit (roughly)?

For Interferometry to work the data from different baselines has to be collected at the same time so waiting 6 months does not help. Spacecraft could theoretically be used to extend the baselines but the volume of data to be transferred is prohibitive with current spacecraft comm tech. Even on Earth they resort to shipping cases of hard drives instead of transferring over the Internet. One technique where simply wait…

> Spacecraft could theoretically be used to extend the baselines but the volume of data to be transferred is prohibitive with current spacecraft comm tech.

Space-based very long baseline interferometry (VLBI) has been done at lower frequencies, most recently with the RadioAstron satellite[0]. There hasn't yet been a VLBI satellite observing at the same frequencies that the EHT uses, but there are mission concepts being discussed. [1] discusses some of the technical challenges.

[0] http://www.asc.rssi.ru/radioastron/

[1] https://arxiv.org/abs/2204.09144

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#74

Post by nerdponx »

mhandley wrote: post #67
mabbo wrote: post #5

> “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.

Any evidence supporting general relativity at these scales is presumably also evidence in favour of dark matter actually being matter, as opposed to gravitational theory needing modification. Seems like we can still learn quite a bit from ruling out alternatives, even if it's not the quick answer we might like.

Why is that the case?

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#75

Post by dotnet00 »

fasteddie31003 wrote: post #29

I 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…

Checking against callibration measurements isn't the only way to do things. With M87's SMBH for instance, they had a simulated image of what they ought to see given general relativity and what they knew about M87. The extracted data matches that fairly closely, thus lending credibility to the result for obtaining parity with physics without actually applying those physics to the data.

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#76

Post by ohgodplsno »

BurningFrog wrote: post #50
onceiwasthere wrote: post #14

Earlier quoted context omitted.

They want an exciting disruption to current theory.

Basically they're bored/want mysteries to solve.

We're kind of at a dead end between both leading theories. A counterexample to either of them would mean that we got it wrong somewhere, and might help us figure out where, potentially unlocking more later.

You wouldn't be surprised if your door opened just as usual when you put your key in the lock. The day it starts jamming however, you get very interested.

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#77

Post by bell-cot »

jrgd wrote: post #32

I 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.

True.

OTOH, consider the potential downsides to living in a galaxy where the central black hole was far bigger, brighter, and cooler-looking...

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#78

Post by boschnix »

markus_zhang wrote: post #19
adgjlsfhk1 wrote: post #17

Earlier quoted context omitted.

GR and quantum field theory don't work together, so at least one of them is wrong, and it would be good to figure out which and how.

Thanks. Can you please point me to some popular science article that explains why the two do not agree with each other?

I liked Sean Carroll's take on this with Steven Strogatz in the recent episode of Joy of Why.

https://www.quantamagazine.org/where-do-space-time-and-gravi...

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#79

Post by bjelkeman-again »

exhilaration wrote: post #62
kloch wrote: post #41

Earlier quoted context omitted.

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…

I also want to point out that the mass around Sagittarius A* is rapidly shifting which makes getting a sharp image still harder. From the NYT: Sagittarius A*, the black hole in the Milky Way galaxy, is a harder target. It is less than one-thousandth the mass and size of the M87 hole and, therefore, evolves a thousand times faster. The M87 black hole barely budges during a weeklong observing run, but Sagittarius A* ch…

M87, according to the original link is 1000x the mass of Sag A, which has a diameter 17x that of our sun. It is mind (and space) bending.

Re: Astronomers reveal first image of the black hole at the heart of our galaxy

#80

Post by [deleted] »

JohnBooty wrote: post #69
exhilaration wrote: post #62

Earlier quoted context omitted.

I also want to point out that the mass around Sagittarius A* is rapidly shifting which makes getting a sharp image still harder. From the NYT: Sagittarius A*, the black hole in the Milky Way galaxy, is a harder target. It is less than one-thousandth the mass and size of the M87 hole and, therefore, evolves a thousand times faster. The M87 black hole barely budges during a weeklong observing run, but Sagittarius A* ch…

Wow, that's incredible. Is that because of all the material the black hole is "devouring?"

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