Question Actual size of Sagittarius *A

Jun 23, 2021
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We hear a lot about the mass of objects in the universe. Like an exoplanet was the size of earth but has the mass of 1.5 earths. So my question is even though the black hole in the Milky Way super massive what is it's actual size. Is it many light years across or is it very small like neutron stars, small yet incredibly heavy
 
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IG2007

"Don't criticize what you can't understand..."
Apr 5, 2020
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We hear a lot about the mass of objects in the universe. Like an exoplanet was the size of earth but has the mass of 1.5 earths. So my question is even though the black hole in the Milky Way super massive what is it's actual size. Is it many light years across or is it very small like neutron stars, small yet incredibly heavy
Foxred,

According to Wikipedia, the radius of the Event Horizon of Sagittarius A* is 22 million km.
 
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Catastrophe

The devil is in the detail
IG, I agree the event horizon is a good choice. Some measurements do not specify exactly what they mean.

NASA gives: Supermassive Black Hole Sagittarius A* | NASA

Supermassive Black Hole Sagittarius A* | NASA Aug 29 2013

"The large image contains X-rays from Chandra in blue and infrared emission from the Hubble Space Telescope in red and yellow. The inset shows a close-up view of Sgr A* in X-rays only, covering a region half a light year wide. The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. This hot gas originates from winds produced by a disk-shaped distribution of young massive stars observed in infrared observations."

Corresponds to radius: 4.75 trillion km 2,375,000,000,000 km

View: https://imgur.com/a/EzjjWJr


Cat :)
 
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Catastrophe

The devil is in the detail
IG, to further my point, I quote the following from the Oxford Dictionary of Astronomy:

Quote
"A prominent radio source 28,000 light years away . . . . . . . . . This highly complex region consists of a central core about 50 light years in diameter connected to a band of arched, parallel filaments more than 300 light years long crossing at right angles to the galactic plane . . . . . . "
Quote
 
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IG2007

"Don't criticize what you can't understand..."
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IG, I agree the event horizon is a good choice. Some measurements do not specify exactly what they mean.

NASA gives: Supermassive Black Hole Sagittarius A* | NASA

Supermassive Black Hole Sagittarius A* | NASA Aug 29 2013

"The large image contains X-rays from Chandra in blue and infrared emission from the Hubble Space Telescope in red and yellow. The inset shows a close-up view of Sgr A* in X-rays only, covering a region half a light year wide. The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. This hot gas originates from winds produced by a disk-shaped distribution of young massive stars observed in infrared observations."

Corresponds to radius: 4.75 trillion km 2,375,000,000,000 km

View: https://imgur.com/a/EzjjWJr


Cat :)
Cat, isn't that picture just covers a region which is half-a-light-year wide? That does not explicitly state that the Sagittarius A* is half-a-lightyear wide. Does it? :)
 
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Catastrophe

The devil is in the detail
IG, No. My interpretation is that the area of the inset photo is 0.5 x 0.5 ly.

If you ignore the blur around the central 'object', I guess that would be about 1/40th ly across, if that helps.

Cat :)
 
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IG2007

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IG, No. My interpretation is that the area of the inset photo is 0.5 x 0.5 ly.

If you ignore the blur around the central 'object', I guess that would be about 1/40th ly across, if that helps.

Cat :)
Yeah, I mean to say, a blackhole's actual circumference is its Event Horizon, no?
 
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Catastrophe

The devil is in the detail
IG, this is not one of my prime areas. If you look at the X-ray inset, I, for one, could not estimate accurately where or what the centre is. I suppose the X-ray are fanning out a bit, but I don't know how black hole gravitation might affect the picture. Also, I didn't notice if there was any mention of positioning, if that is relevant.

Cat :)
 
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IG2007

"Don't criticize what you can't understand..."
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IG, this is not one of my prime areas. If you look at the X-ray inset, I, for one, could not estimate accurately where or what the centre is. I suppose the X-ray are fanning out a bit, but I don't know how black hole gravitation might affect the picture. Also, I didn't notice if there was any mention of positioning, if that is relevant.

Cat :)
I dunno, Cat, I just copy-pasted from Wikipedia. Maybe the Event Horizon was calculated by Gravitational Lensing? :)
 
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Catastrophe

The devil is in the detail
If you go back to the original, it says:
"The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. This hot gas originates from winds produced by a disk-shaped distribution of young massive stars observed in infrared observations." My emphasis.

Perhaps this gives some clue as to why we cannot accurately estimate the size of the central object from the X-ray data?

Cat :)
 
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Catastrophe

The devil is in the detail
Maybe - I'll go back read the paper again.

"This work should impact efforts using radio telescopes to observe and understand the “shadow” cast by the event horizon of Sgr A* against the background of surrounding, glowing matter."

This is all I can find. Not much help. Sorry.

Cat :)
 
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Yeah.

So, how do you think they calculated the Event Horizon? By Gravitational Lensing?
I think they forgot one little item about a size measure of a black hole from outside it.
Extreme time dilation of the black hole itself making any measure of it from outside just a guess.
We can calculate the mass pretty easy from orbiting stars but the diameter no way to be accurate about a measure in an event horizon and beyond and the diameter is at the event horizon. (if a black hole has such a thing)

Science forgot a basic on this one.
 

Catastrophe

The devil is in the detail
Actual size of Sagittarius *A

Does it really matter if the apparent size (whatever that means) is ten times smaller or ten times larger?

Cat :)

View: https://imgur.com/a/lTuCap1

NASA



Black Hole Image Makes History; NASA Telescopes ...
https://www.nasa.gov › mission_pages › chandra › news

10 Apr 2019 — tempA black hole and its shadow have been captured in an image for the first time, a historic feat by an international network of radio ...
You visited this page on 01/06/21.
 
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Actual size of Sagittarius *A

Does it really matter if the apparent size (whatever that means) is ten times smaller or ten times larger?

Cat :)

View: https://imgur.com/a/lTuCap1

NASA



Black Hole Image Makes History; NASA Telescopes ...
https://www.nasa.gov › mission_pages › chandra › news

10 Apr 2019 — tempA black hole and its shadow have been captured in an image for the first time, a historic feat by an international network of radio ...
You visited this page on 01/06/21.
If the diameter can't be accurate in any measure then the density can't be measured and the true nature of the black hole.
What we measure as diameter from Earth and the true diameter of the black hole is a wild guess.

2 viewpoints from different time perspectives.
Who can even hazard a guess of the true perspective of a black hole beyond an event horizon?
 

Catastrophe

The devil is in the detail
VPE
Is the information available at least sufficient to give you an approximate answer, quoting the limits of accuracy in your computation? I understand that this might be rather inexact.

Cat :)
 
Apr 13, 2021
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Interesting reading on arXiv.org
Sagittarius A Black Hole

As for M87 Black Hole the image showed an area in absence of light. I do not understand how they defined this a Black Hole image.
 
Apr 13, 2021
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You can detect gravitational and massive electromagnetic objects,
The question is this:
How do you define a Blackhole?
Classical blackhole has a singularity and nothing can escape, this very theoretical.
Mimic Blackhole that has the ability to form vortices.
All observation indicate a mimic black hole.

There is so far no evidence of a classical Black Hole.
 
You can detect gravitational and massive electromagnetic objects,
The question is this:
How do you define a Blackhole?
Classical blackhole has a singularity and nothing can escape, this very theoretical.
Mimic Blackhole that has the ability to form vortices.
All observation indicate a mimic black hole.

There is so far no evidence of a classical Black Hole.
I think classical is wrong for one good reason (infinite mass point)
We don't see it happening anywhere in the universe and once beyond the nuclear force it should happen.

Good thing it doesn't since an infinite gravity point would consume the universe. :)

IMO a black hole is neither mass nor singularity.
It can't exist as mass since the nuclear force is overwhelmed so my guess is compresses energy.
Simply a well of slowed time/activity that causes the black hole to never make it to infinite mass since it would take forever to happen.

JMO of course
 
Apr 13, 2021
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Matter has a finite end,
We cannot create or destroy matter.
Research Transients and Condensates from Axion Gluon matter to Neutron matter.
Take your time
 

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