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Sagittarius A*

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TimFox:

--- Quote from: dunkemhigh on May 14, 2022, 05:37:36 pm ---
--- Quote ---If the accretion disk is visible as a ring from earth, it seems to be near orthogonal to the plane of our galaxis
--- End quote ---

The initial video from Veritasium explains that the accretion disk would appear to be orthogonal regardless of it's actual attitude (jump to around 19:45).

--- End quote ---

My understanding is that the reconstruction from interferometric data, being two dimensional with multiple baselines, produces a map in a plane orthogonal to the vector from the terrestial locations of the observatories to the object being imaged, which vector would be in (very close to) the galactic plane for an object near the center of the galaxy.

aetherist:

--- Quote from: dunkemhigh on May 14, 2022, 10:08:45 am ---
--- Quote ---214 times 214 is 46,000 pixels of resolution.
32,000,000 pixels (the pixels in their blackhole image) divided by 46,000 is 700.
Hence the resolution of their blackhole image is  700 times the resolution of their array.
--- End quote ---

I think you are conflating capture resolution with display resolution.
--- Quote ---According to Pierre Marie Robitaille
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Maybe you should treat what he says more critically.
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Yes capture resolution is 1/700 times the display resolution.
Have u seen/heard what Robitaille says?
His ground breaking MRI development probly was not based on array interference, but his analysis of the horizon array interference method looks good to me (if i could understand it).

PlainName:

--- Quote ---Have u seen/heard what Robitaille says?
--- End quote ---

Precis the relevant part. I'm not going to sit through 3 hours of random videos trying to figure out which bit you think will make your point. If you understand it you can say it yourself.

aetherist:

--- Quote from: dietert1 on May 14, 2022, 12:19:22 am ---The massive object has an event horizon. The physics inside the event horizon is unknown and it will remain unknown. Everybody can use their own fantasy. For a scientist a singularity is enough of a model.
Of course the new images don't show the black hole but its cosmic ambient outside of its event horizon. As far as i understand gravitational red shift makes hard x-ray radiation observable as mm waves here on earth.
Regards, Dieter
--- End quote ---
I am thinking that xrays created near a blackhole would be created by atomic processes that are slower due to slower ticking of atomic processes due to the slowing of light & em radiation near a blackhole.
If so then the supposed xrays created near a blackhole would have a slower frequency (instead of having an xray frequency), ie they would have the same frequency as say ultraviolet radiation (depending on how far they were created from the blackhole).
Then when the ultraviolet frequency radiation reaches Earth it would be still have an ultraviolet frequency.
But u might be correct, it might have been a microwave all along (if it was created very close to the blackhole).
Anyhow i would not call that a redshift.
And of course i don’t believe in blackholes, but i do believe in supermassive bodies (brown holes).

TimFox:
An interesting thing in the real physics of black holes in General Relativity is the case where the body is axially-symmetric (around a rotation axis) with angular momentum.  This is the "Kerr metric".
(The earlier Schwarzschild metric is for a spherically-symmetric case, where the body is not rotating.)  The math is very complicated, and I won't quote any of it here, but it is covered in the real textbooks, and even in Wikipedia.
It was published in 1963, followed by the "Kerr-Newman" metric for a rotating charged object.
A collapsed object that obeys this metric, as Sag A* is described to be, has two event horizons, instead of the single one in the Schwarzschild metric.
It leads to the "Penrose process" (q.v.), which can lead to loss of energy from the hole due to weird stuff happening between the two horizons.
This stuff was still new (1971) when I started grad school, and there was much discussion about the implications (which interested me, but I studied other stuff), since Chicago had a strong Astrophysics department.
Perhaps the best summary is in Chandrasekhar, Subrahmanyan (1999) Mathematical Theory of Black Holes Oxford University Press. ISBN 0-19-850370-9.
The late Prof. Chandrasekhar, whose name lives on in the modern x-ray observatory satellite, was the wisest man I ever had the fortune to meet (although I doubt he remembered me).

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