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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

#151

Post by marricks »

fsh wrote: post #125
hammock wrote: post #113

Earlier quoted context omitted.

How sharp do we expect an infinite-res picture to be?

The resolution of these telescopes is limited by diffraction, not by the number of pixels on the sensors. The achievable angular resolution is roughly the wavelength divided by the aperture diameter [1]. JWST works in the few µm wavelength range and has a 6.5 m aperture, such that the angular resolution is ~0.1 arcsec. The EHT works with 1.3 mm wavelength and has an effective aperture of roughly the earth diameter (~…

Then why did we build the JWST! /s

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

#152

Post by [deleted] »

kloch wrote: post #41
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.

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…

[deleted]

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

#153

Post by sailingparrot »

jankovicsandras wrote: post #136
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…

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…

While the skepticism of the comment you are replying to is understandable, yours is not.

"Visible light" is not a better or truer electromagnetic spectrum than x-ray or radio. It's a human construct only defined by what our human eyes have evolved to capture, based on what is most useful for us here on earth, nothing more.

There is nothing wrong with getting measurement of an object in any random frequency that happens to be the most interesting/practical. Rendering those results as an image in visible light is also simply the best way to visualize the results for us humans. It is certainly more understandable than hundreds of plots.

> It's a bit like an alien scientist showing an X-ray picture of a skeleton

If that alien organism has evolved to see x-rays, as it might be the most useful spectrum for their particular environment, they would find your comment quite puzzling as that would be exactly what they would see should they meet us.

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

#154

Post by babypuncher »

sillysaurusx wrote: post #108
zeven7 wrote: post #90

Earlier quoted context omitted.

It seems the common expectation is that GR is more likely to be the theory that needs to be modified the most - or more or less tossed out and replaced with a quantum theory of gravity. Is it possible that GR is just "right" and QM needs to be modified to fit into it?

The most likely explanation is that we have no clue, just like every other point in history. Science is always new. Everyone is different, but most scientists seek areas where experiment doesn’t match the predictions. It’s the only way we learn. One such instance is the W Boson Anomaly: https://vm.tiktok.com/ZTdpwrmoj/?k=1 If the equations were right, the experimental error would be zero (modulo uncertainty bars). In…

Back when Trump was making a big stink about TikTok I didn't understand it, because my feed was almost exclusively high quality short form educational content from physicists, doctors, linguists, etc. It's a great format for people who want to share their knowledge with the public in a way that is easy to digest, but do not have time to script and edit 15+ minute videos.

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

#155

Post by hammock »

fsh wrote: post #125
hammock wrote: post #113

Earlier quoted context omitted.

How sharp do we expect an infinite-res picture to be?

The resolution of these telescopes is limited by diffraction, not by the number of pixels on the sensors. The achievable angular resolution is roughly the wavelength divided by the aperture diameter [1]. JWST works in the few µm wavelength range and has a 6.5 m aperture, such that the angular resolution is ~0.1 arcsec. The EHT works with 1.3 mm wavelength and has an effective aperture of roughly the earth diameter (~…

Should have clarified. Does a black hole have fuzzy edges or sharp edges?

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

#156

Post by belter »

MeteorMarc wrote: post #116
wthomp wrote: post #91

For those wondering if we could get sharper images with JWST, here’s the previously imaged black hole (same angular size as our own) compared to a single pixel from Hubble’s wide field camera 3: https://twitter.com/alex_parker/status/1116070667068170240?s... JWST will have smaller “pixels” but is in the same ballpark.

And here you see the new picture compared with the 2019 picture of Messier 87: https://blackholecam.org/

Similar comparison in size.

"Size comparison of the two EHT black holes": https://youtu.be/UOESt-G34vE

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

#157

Post by SkyMarshal »

wthomp wrote: post #91

For those wondering if we could get sharper images with JWST, here’s the previously imaged black hole (same angular size as our own) compared to a single pixel from Hubble’s wide field camera 3: https://twitter.com/alex_parker/status/1116070667068170240?s... JWST will have smaller “pixels” but is in the same ballpark.

So you’re saying no, JWST won’t provide significantly sharper images of black holes than the Event Horizon Telescope?

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

#158

Post by drewrv »

lordnacho wrote: post #128
zeven7 wrote: post #66

Earlier quoted context omitted.

Relatedly, before general relativity, people already knew something was wrong with Newton's theory of gravity from observing the orbit of Mercury, which didn't follow the theory accurately. At that time Mercury, being so close to the Sun, was an extreme condition that showed the flaws in the theory. The fact that general relativity continues to hold up to every observation we can make is remarkable.

Could it happen that the universe simply never provides us with the required evidence? Eg if there's an anomaly but only when something that never happens happens. Like a large enough mass/charge/etc or some flavor of unlikely coincidental occurrence, like an eclipse is a bit of a coincidence.

I've heard it said as "The universe is under no obligation to make sense to us". It's possible that the events where the two theories diverge will always be out of reach for us to observe.

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

#159

Post by belter »

wumpus wrote: post #34
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…

Didn’t I already reply to you weeks ago about a similar comment? Now you can read the actual papers which explain in detail why your comment is incorrect.

I think you are talking about the conversation we had here. So in this case you replied to a different person.

https://news.ycombinator.com/item?id=31281773

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