Questions tagged [sagittarius-a]

Questions about Sagittarius A*, abbreviated Sgr A*, the "bright and very compact astronomical radio source at the center of the Milky Way" galaxy, believed to be the result of a supermassive black hole.

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5 votes
2 answers
612 views

How does the Event Horizon Telescope implement the interferometry?

The BBC article Event Horizon Telescope ready to image black hole describes the Event Horizon Telescope, a coordinated observing technique with several radio telescope arrays across the globe forming ...
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15 votes
1 answer
2k views

What is it exactly about these flares of infrared light from Sgr A* that "confirms" it is a supermassive black hole?

CNET.com's SCI-TECH Scientists confirm a 'supermassive black hole' at the heart of our galaxy It's "mind-boggling", they say. This links to Astronomy.com's Scientists finally confirm the Milky Way ...
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27 votes
2 answers
8k views

Why didn't the Event Horizon Telescope team mention Sagittarius A*?

At the press conference this morning, the Event Horizon Telescope team didn't say much about Sagittarius A*, which was the target many of us have been waiting for. Is there any explanation anywhere ...
12 votes
1 answer
1k views

How did they make a video of the center of the galaxy, and what is it exactly that's flashing there?

The ESA video ESOcast 173: First Successful Test of Einstein’s General Relativity Near Supermassive Black Hole includes a clip of images of stars at the center of our galaxy orbiting around SgrA*, a ...
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3 votes
1 answer
302 views

How will they know when to start taking the picture of the black hole at the center of the Milky Way?

@csm's answer to Why not take a picture of a closer black hole? points out that it's necessary for the supermassive black hole at the center of a galaxy to be actively feeding for it to generate a ...
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14 votes
2 answers
2k views

Why does the closest approach of star S2 to Sgr A* not appear to be near the focus of its elliptical orbit?

Phys.org's Very Large Telescope sees star dance around supermassive black hole, proves Einstein right links to several ESO videos, including The star S2 makes a close approach to the black hole at the ...
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4 votes
1 answer
216 views

How feasible is it that we could see the Central Black Hole Sgr A* occlude one of it's closely orbiting stars?

I'm thinking about the recent famous photo of a black hole, some months ago. It got me wondering if there isn't a way to more easily make a direct observation of these. We detect exoplanets in part ...
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4 votes
1 answer
384 views

How did they measure the distance to the center of our galaxy to 0.3% accuracy?

The abstract of A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty (Open Access) says: We present a 0.16% precise and 0.27% accurate determination of R₀, the ...
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2 votes
1 answer
211 views

How did they estimate the mass of Sgr A*'s companion G2 without knowing what it was?

Gizmodo.com's Astronomers Spot Unprecedented Flashes From Our Galaxy's Black Hole mentions Sgr A*'s companion gas cloud G2. That Wikipedia article says: First noticed as something unusual in ...
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8 votes
1 answer
253 views

Is the appearance of accretion disks of M87 and Sgr A* in EHT image, related to the nucleus being active or non-active?

I'm a newbie in this field so forgive me if I'm considering things wrong. As much as I can see, the newly published image of the Sgr A* looks pretty much the same as M87 released years ago. I'm ...
6 votes
1 answer
528 views

Forms of stellar orbits around the galactic center

Do all stars in orbit around Sagittarius A have approximately circular orbits or are there stars that orbit the Milky Way center very elliptically, like being in the Milky Way's outer rim at apoapsis ...
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6 votes
2 answers
372 views

Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*?

Do we know at which angle the Event Horizon Telescope will look at the accretion disk of Sagittarius A*? Additionally, would it matter if we are exactly in the plane with the accretion disk, i.e. ...
5 votes
1 answer
98 views

Nature and mechanism of the short-term variability in radio strength of Sgr A*?

The Phys.org article Cosmic filament probes our galaxy's giant black hole links to A Nonthermal Radio Filament Connected to the Galactic Black Hole? which discusses (among other things) the importance ...
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3 votes
2 answers
180 views

How can I obtain raw observation data of stars surrounding Sgr A*?

Are there any publicly available telescope that offers the sensitivity to observe the stars surrounding Sgr A*? If not, is there any raw data available that I could download?
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2 votes
1 answer
60 views

What does "synchrotron emission from relativistic electrons in equipartition with a ∼1.5 mG magnetic field" mean?

I've heard of the equipartition theorem in the context of thermodynamics. But I don't understand how either "synchrotron emission" or "relativistic electrons" can be in "...
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