Another Large Black Hole In 'Our' Galaxy (arxiv.org) 46
RockDoctor (Slashdot reader #15,477) writes:
A recent paper on ArXiv reports a novel idea about the central regions of "our" galaxy.
Remember the hoopla a few years ago about radio-astronomical observations producing an "image" of our central black hole — or rather, an image of the accretion disc around the black hole — long designated by astronomers as "Sagittarius A*" (or SGR-A*)? If you remember the image published then, one thing should be striking — it's not very symmetrical. If you think about viewing a spinning object, then you'd expect to see something with a "mirror" symmetry plane where we would see the rotation axis (if someone had marked it). If anything, that published image has three bright spots on a fainter ring. And the spots are not even approximately the same brightness.
This paper suggests that the image we see is the result of the light (radio waves) from SGR-A* being "lensed" by another black hole, near (but not quite on) the line of sight between SGR-A* and us. By various modelling approaches, they then refine this idea to a "best-fit" of a black hole with mass around 1000 times the Sun, orbiting between the distance of the closest-observed star to SGR-A* ("S2" — most imaginative name, ever!), and around 10 times that distance. That's far enough to make a strong interaction with "S2" unlikely within the lifetime of S2 before it's accretion onto SGR-A*.)
The region around SGR-A* is crowded. Within 25 parsecs (~80 light years, the distance to Regulus [in the constellation Leo] or Merak [in the Great Bear]) there is around 4 times more mass in several millions of "normal" stars than in the SGR-A* black hole. Finding a large (not "super massive") black hole in such a concentration of matter shouldn't surprise anyone.
This proposed black hole is larger than anything which has been detected by gravitational waves (yet) ; but not immensely larger — only a factor of 15 or so. (The authors also anticipate the "what about these big black holes spiralling together?" question : quote "and the amplitude of gravitational waves generated by the binary black holes is negligible.")
Being so close to SGR-A*, the proposed black hole is likely to be moving rapidly across our line of sight. At the distance of "S2" it's orbital period would be around 26 years (but the "new" black hole is probably further out than than that). Which might be an explanation for some of the variability and "flickering" reported for SGR-A* ever since it's discovery.
As always, more observations are needed. Which, for SGR-A* are frequently being taken, so improving (or ruling out) this explanation should happen fairly quickly. But it's a very interesting, and fun, idea.
Remember the hoopla a few years ago about radio-astronomical observations producing an "image" of our central black hole — or rather, an image of the accretion disc around the black hole — long designated by astronomers as "Sagittarius A*" (or SGR-A*)? If you remember the image published then, one thing should be striking — it's not very symmetrical. If you think about viewing a spinning object, then you'd expect to see something with a "mirror" symmetry plane where we would see the rotation axis (if someone had marked it). If anything, that published image has three bright spots on a fainter ring. And the spots are not even approximately the same brightness.
This paper suggests that the image we see is the result of the light (radio waves) from SGR-A* being "lensed" by another black hole, near (but not quite on) the line of sight between SGR-A* and us. By various modelling approaches, they then refine this idea to a "best-fit" of a black hole with mass around 1000 times the Sun, orbiting between the distance of the closest-observed star to SGR-A* ("S2" — most imaginative name, ever!), and around 10 times that distance. That's far enough to make a strong interaction with "S2" unlikely within the lifetime of S2 before it's accretion onto SGR-A*.)
The region around SGR-A* is crowded. Within 25 parsecs (~80 light years, the distance to Regulus [in the constellation Leo] or Merak [in the Great Bear]) there is around 4 times more mass in several millions of "normal" stars than in the SGR-A* black hole. Finding a large (not "super massive") black hole in such a concentration of matter shouldn't surprise anyone.
This proposed black hole is larger than anything which has been detected by gravitational waves (yet) ; but not immensely larger — only a factor of 15 or so. (The authors also anticipate the "what about these big black holes spiralling together?" question : quote "and the amplitude of gravitational waves generated by the binary black holes is negligible.")
Being so close to SGR-A*, the proposed black hole is likely to be moving rapidly across our line of sight. At the distance of "S2" it's orbital period would be around 26 years (but the "new" black hole is probably further out than than that). Which might be an explanation for some of the variability and "flickering" reported for SGR-A* ever since it's discovery.
As always, more observations are needed. Which, for SGR-A* are frequently being taken, so improving (or ruling out) this explanation should happen fairly quickly. But it's a very interesting, and fun, idea.
"our" galaxy? (Score:5, Insightful)
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"But that large group of stars it is also located in "the" galaxy, because everything is."
That would be 'the' universe.
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Re: "our" galaxy? (Score:5, Funny)
You are right off course, but common language is not as precise as the scientific language. So alas it is "The Hitchhiker's Guide to the Galaxy", but it still has a volume "The Restaurant at the End of the Universe". In this case, Galaxy and Universe mean the same thing.
1. I think you meant to type "of" course."
2. Arguing that Douglas Adams used "Galaxy" and "Universe" to mean the same thing doesn't really work to begin with, and it would be within the spirit of your post to point out that the babelfish in your ear should've provided an unambiguous word.
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It's our galaxy even if there are lots of other folks that also call it their galaxy. "My house" is the house that I live in. It doesn't always imply ownership.
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With two black holes in the yard.
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Trump declared Andromeda Galaxy (Score:1)
...part of the Milky Way, per Manifest Destiny. After all, he is the Chosen One, he even said so.
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Unless he protests for Palestinians. Then he'll get deported to Sagittarius.
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It should be The Galaxy of America!
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One is squashed underfoot by a landing secretary bird (I may be stretching my knowledge of African savannah ecology here), which then eats the other one.
"Our" ??
Why the "quotes" everywhere? (Score:5, Funny)
There's a lot of "stuff" in quotes. Most of the stuff does "make sense" to be in quotes. It's quite "annoying" to read that synopsis, so I'm not going to go reading the "article" itself.
Re:Why the "quotes" everywhere? (Score:4, Funny)
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by Parenthy McQuotie
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The article in question is the scientific paper, so no silly "quote" "marks" there.
"They" just come from the "person" who "submitted" this "to" slashdot.
Spock! I do not ... pause my ... speech! -Jim (Score:1)
> "They" just come from the "person" who "submitted" this "to" slashdot.
When I submit stories to Slashdot, the editor(s) usually shuffle it around quite a bit, so I'd expect they'd clean up the quotes. Vacation?
I notice if you interpret quoted words as pauses, it reads like Captain Kirk's delivery.
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But I'm not doing it tonight.
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What we want to know is (Score:2)
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Learn to write (Score:2)
Why can't people write without using "words"?
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Reads like somebody just transcribed researcher notes as-is without bothering to pay for a real editor.
Divided by zero (Score:2)
Ok who fucking divided by zero? Anyone want to fess up? Was it you Leroy Jenkins??
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Black holes are where God divided by zero.
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That is how I think about them intuitively. I really don't know if the math matches up though.
what if they collide? (Score:2)
Every time I screw up a photo (Score:1)
...can I just claim "there's a black hole in front of it"?
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I ever knew how closely black holes resembled the human thumb!
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Dark Thumb, the latest mystery force/substance.
Line of sight? Who put it there? (Score:2)
How likely are two black holes aligned with _our_ line of sight? Is this done by a "designer" then? /s
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The star grinder model (Score:2)
I was reading an article just yesterday about black holes at the center of the galaxy.
"Based on their model, the researchers conclude that the center of the Milky Way could host up to 100 million black holes per cubic parsec—a staggering number that would make this region the most densely populated with black holes in the galaxy."
https://www.msn.com/en-us/scie... [msn.com]
And if that's the case it wouldn't be at all unusual for there to be one or more in our line of sight to the central black hole. A parsec is
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Entirely agree.
Another job for Beowulf Shaeffer (Score:2)
He's good for these jobs.
*Squint* (Score:2)
Need more resolution.
"Dark Quotes" are sign of end times (Score:2)
we are "doomed"! They end "up" around everything, and I mean "everything", like the worst kind of seaweed tangled in a boat "propeller". Eventually "there" will be no ""room"" for ""regular"" words"!"