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ALMA watches Sgr A* twinkle

Posted: Fri May 22, 2020 10:57 pm
by notFritzArgelander
Note that this is the reason why the effort to image the event horizon failed but M87* succeeded,

https://phys.org/news/2020-05-alma-twin ... milky.html

Re: ALMA watches Sgr A* twinkle

Posted: Sun May 24, 2020 1:49 am
by Michael131313
Thanks nFA. Is the distance to M87 the reason we do not see this type of variation or does M87 not have these types of accretion disc variations?

Re: ALMA watches Sgr A* twinkle

Posted: Sun May 24, 2020 2:36 am
by notFritzArgelander
Michael131313 wrote: Sun May 24, 2020 1:49 am Thanks nFA. Is the distance to M87 the reason we do not see this type of variation or does M87 not have these types of accretion disc variations?
Actually no! Good question!

Sgr A* is 4 million solar masses.
M87* is 2,400 billion solar masses.

So it’s 600,000 times more massive and larger in size similarly. The time scale for fluctuations is longer by the same factor.

Relativity requires the fluctuations be longer than the light speed crossing time roughly. So variations are slower and don’t blur the picture. :)

Re: ALMA watches Sgr A* twinkle

Posted: Sun May 24, 2020 3:17 pm
by helicon
I assume the mass of the black hole in M87 far exceeds that of Sagittarius A.

Re: ALMA watches Sgr A* twinkle

Posted: Sun May 24, 2020 10:08 pm
by notFritzArgelander
helicon wrote: Sun May 24, 2020 3:17 pm I assume the mass of the black hole in M87 far exceeds that of Sagittarius A.
Yes by a factor of 600,000. The M87* object flickers more slowly by the same factor as you can see from these images.

https://aasnova.org/2019/04/10/first-im ... telescope/