Live data from Hacker News

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

public.nrao.edu

251–260 of 329 posts

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

#251
post #36

Earlier quoted context omitted.

Why do you think you know more about astronomy than a team of scientists publishing peer reviewed information?

Sorry but as this is a press conI doubt the thing has really passed “peer review” properly speaking. There was some hype about: FTL events, life based on cyanide not phosphorus… Careful with “peer review” when the set of peers is invested in the same type of results.

We published 10 papers today.

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

#252

Earlier quoted context omitted.

Criticism must bring substance as well. Sure, anyone can sit back and say “I don’t believe this, prove it better.” But without specific claims, such criticism can’t ever be answered and the conversation is not constructive or particularly scientific. One constructive approach to criticism here would be to take the documented imaging process and apply it to other data. If it produces results that don’t match existing…

I don’t know, the criticism in OP seems pretty substantive to me. I don’t know much about this subject so I can’t really weigh in on how much the post makes sense but regardless appeal to authority is essentially the opposite of modern science. That’s why nullius in verba has been a motto of science for 300+ years. On that point, scientists don’t need you to chastise people for questioning their authority online. I t…

>I don’t know much about this subject so I can’t really weigh in on how much the post makes sense but [...]

Then how can you say the criticism seems substantive? He brings nothing to the table to show that his criticism is valid, it's basically "I don't like, therefore wrong". The proper way criticize their paper would be conduct your own experiments using their parameters and methodologies and show that the results you obtain do not match theoretical results or results of other observations through other means.

>On that point, scientists don’t need you to chastise people for questioning their authority online. I think a lot of them would be offended at the idea that you think that is what they want.

We question their authority on this specific subject they seem to be criticizing. If you make a claim without having at least the background to support said claim, what value does it have? It's the same as a person without background in microbiology or virology claiming vaccines don't work when they don't even begin to understand the science behind it and the mountain of evidence that says otherwise.

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

#253

I am impressed. I have a few ignorant questions: 1. There are three bright blobs on the image; I assume they are the same object, behind the BH. What are they/is it? They said the image was averaged; so presumably whatever the blobs are wasn't moving? 2. Is it correct that the rest of the ring, ignoring the three blobs, is the far side of the accretion disk? Why can't I see this side of the accretion disk? 3. Accordi…

> 3. According to the article, at least one submillimeter telescope was important. But submillimeter is infrared, isn't it? I thought infrared was blocked by dust, and if there's one thing there's a lot of at the centre of the galaxy, it's dust?

It's the opposite actually! Infrared light is able to go through dust.

> Another reason [to look at the universe in the infrared] is because stars and planets form in clouds of gas and dust, and this dust obscures our view. Infrared light penetrates these clouds and allows us to see inside.

https://www.nasa.gov/content/goddard/webb-conversations-its-...

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

#254

Very interesting. The previously-released M87 image had just a single "shadow", but this one (of Sag A*) has multiple bright "lumps". Maybe it's in the linked papers which I haven't gotten to yet, but why the difference? Is it due to the observation method or does it reflect a real difference? Or both?

From the announcement presentation, this happened due to this image being an average of many, many different images. Due to it's size, the motion of the accreting material around SgtA* moves much, much faster relative it than the material around M87. While the accreting material around both BHs move at similar speeds, M87 is about 2000x more massive than SgtA. Due to that, the material around M87 takes weeks to orbit it, while the material around SgtA takes hours. Since each data point can be minutes or hours apart, the final image for a single data point can vary greatly between other measurements, and thus the need to average everything. To put things in perspective, we just confirmed through this image that SgtA*'s shadow is about the size of the orbit of Mercury around the Sun. M87's shadow, on the other hand, has a radius larger than the distance of the Voyager probe to the Sun.

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

#255

Earlier quoted context omitted.

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.

I'd just like to disentangle criticisms of the practice of peer review from whether this commenter is an expert or not. The former is valid or invalid irrespective of the latter.

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

#256

Earlier quoted context omitted.

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.

Peer review has let plenty of bad science through. Don't burn me at the stake because I speak heresy against the holy theologians of astronomy.

You might try publishing that comment as a dialog, but try not to ridicule the Pope's position too harshly, though. It didn't end up well for Galileo.

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

#257

Earlier quoted context omitted.

Why would that matter at this scale ?

Black holes are extreme enough to be one of the places where both can matter.

Scale was not the right word - maybe I meant distance or resolution. Does QM make a prediction that could be falsified at this resolution?

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

#258
post #253

I am impressed. I have a few ignorant questions: 1. There are three bright blobs on the image; I assume they are the same object, behind the BH. What are they/is it? They said the image was averaged; so presumably whatever the blobs are wasn't moving? 2. Is it correct that the rest of the ring, ignoring the three blobs, is the far side of the accretion disk? Why can't I see this side of the accretion disk? 3. Accordi…

> 3. According to the article, at least one submillimeter telescope was important. But submillimeter is infrared, isn't it? I thought infrared was blocked by dust, and if there's one thing there's a lot of at the centre of the galaxy, it's dust? It's the opposite actually! Infrared light is able to go through dust. > Another reason [to look at the universe in the infrared] is because stars and planets form in clouds…

OK, that explains that; thanks.

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

#259

Earlier quoted context omitted.

The point spread function of the detector is pretty well characterized, and from there the image is basically just a Fourier transform. It's not as magical as you might think. Then it looks like they average a bunch of these images to get a maximum likelihood image. What is your issue with that? Besides, to calibrate on a known celestial body, they'd have to have another micro-arcsecond resolution radio telescope to…

Could they not zoom out and take a picture of the stars around Sagittarius A* to compare that to the knowns locations of these stars?

They absolutely could, but doing so would be a pointless waste of nontrivial resources.

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

#260

This image apparently has not captured as much attention as the image of M87, but anyway, I have a question, maybe someone with the knowledge can answer: Between the images of M87 and Sgr A, one noticeable difference is that the image of M87 appears to have a single cluster of light "below" the blackhole whereas the image of Sgr A has three surrounding the blackhole. Is this because of the mass and spin differences b…

> This image apparently has not captured as much attention as the image of M87

To be fair, to most non-scientific people the two photos look basically the same, and "orange halo" kinda loses it's appeal quickly

Post reply on HN