APOD: Ring Galaxy AM 0644-741 (2021 Jul 28)

Comments and questions about the APOD on the main view screen.
roland jochems
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Joined: Fri Jul 30, 2021 2:58 pm

Re: APOD: Ring Galaxy AM 0644-741 (2021 Jul 28)

Post by roland jochems » Sun Aug 01, 2021 2:27 pm

Chris Peterson wrote:
Fri Jul 30, 2021 10:49 pm
JohnD wrote:
Fri Jul 30, 2021 10:27 pm
Chris Peterson wrote:
Fri Jul 30, 2021 5:27 pm

It's not. Black holes can't be optically resolved. They're far too small.
Not the BH itself, but the accretion disk, around the event horizon?
Like this?
Black hole EHT image.png
No. A BH and an accretion disc are unresolvable in light at any distance from us where we expect to find them. Images like you provide are produced by radio telescopes with planetary scale apertures (interferometers), yielding a resolution of about 20 microarcseconds, and therefore able to resolve structures in nearby galaxies with sizes of a few hundred AU (or a few hundredths of a light year).

Whatever that spot in this image is (I'm inclined to agree with Ann, that it's a dust cloud), it must be many light years across.
Thanks, for the explanation. I agree it is most likely dust. Still the fact that it is a spere maybe it is a lot closer within a few light years or less. Does it show in other images, if any, taken of this galaxy?

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Re: APOD: Ring Galaxy AM 0644-741 (2021 Jul 28)

Post by Ann » Mon Aug 02, 2021 6:27 am

Ann wrote:
Fri Jul 30, 2021 8:16 pm
Speaking of ring galaxies, I just found a picture of the Andromeda Galaxy in radio waves (at 6.6 GHz) and I just have to share it with you.

I hope this link isn't going to break! But in any case...

Is the Andromeda Galaxy a ring galaxy, or is it a ring galaxy?


So it broke! Okay, I'll try again:
Radio image of Andromeda galaxy at 6.6 GHz (inset), captured using
the Sardinia Radio Telescope in Italy. Credit: S. Fatigoni et al. (2021)

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