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Another Large Black Hole In 'Our' Galaxy (arxiv.org) 49

Posted by EditorDavid from the dark-stars dept.
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.

Another Large Black Hole In 'Our' Galaxy More | Reply

Another Large Black Hole In 'Our' Galaxy

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  • "our" galaxy? (Score:5, Insightful)

    by hcs_$reboot ( 1536101 ) on Monday March 24, 2025 @04:30AM (#65255127)
    "our" galaxy is our galaxy, and it remains our galaxy until proven otherwise. And so far, we're the only ones who can lay claim to it being our galaxy.
    • "our" galaxy is what you see as the Milky Way (if you live in an area without light pollution, that is). But that large group of stars it is also located in "the" galaxy, because everything is.

      • Re: (Score:1)

        by Shaitan ( 22585 )

        "But that large group of stars it is also located in "the" galaxy, because everything is."

        That would be 'the' universe.

        • 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.

          • Re: "our" galaxy? (Score:5, Funny)

            by ElimGarak000 ( 9327375 ) on Monday March 24, 2025 @10:38AM (#65255557)

            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.

    • Re: (Score:2)

      by HiThere ( 15173 )

      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.

    • ...part of the Milky Way, per Manifest Destiny. After all, he is the Chosen One, he even said so.

    • Re: (Score:2)

      by spitzak ( 4019 )

      It should be The Galaxy of America!

    • Two fleas are on an elephant's back, arguing about who really owns "our elephant".

      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)

    by Tomahawk ( 1343 ) on Monday March 24, 2025 @05:00AM (#65255147) Homepage

    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.

  • Is this gonna affect the neighbourhood's house prices?
    • Only if you have a Daily Flail reading neighbour. Which will already have lowered the tone of the neighbourhood.

  • Why can't people write without using "words"?

    • Re: (Score:1)

      by Tablizer ( 95088 )

      Reads like somebody just transcribed researcher notes as-is without bothering to pay for a real editor.

  • Ok who fucking divided by zero? Anyone want to fess up? Was it you Leroy Jenkins??

  • will it blow the Milkyway apart?
    • Did you read the sentence in summary where I typed "(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".)"?

      I wrote those words (explaining the paper's wording) because I thought that users might think of precisely this question.

      Sigh - not even reading the fucking summary.

  • ...can I just claim "there's a black hole in front of it"?

  • How likely are two black holes aligned with _our_ line of sight? Is this done by a "designer" then? /s

    • Since the inner part of the Milky Way is a highly dynamic region (did you read the bit I wrote about the 26 year orbit of the S2 star? It wasn't edited out.) it's unlikely that the alignment is enduring. The 2017 data (published in 2020, producing the image I linked to) was collected over a number of months, and is an average of the appearance during the duration of that imaging. What it looks like "now" (considering that a repeat observation to that resolution would probably take months to complete) is any

  • 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

    • I was reading the same paper (https://arxiv.org/pdf/2503.15598) this morning.

      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.

      Entirely agree.

    • Yeah, that was an interesting paper. Convenient timing that it appeared out of my bit bucket at almost the same time as this thread's subject.

      I remember one of the author's names - Kroupa. Can't remeber where from though.

      Précising it :

      A model for forming the SMBH : build a very large ("hypermassive" - uggh! ; save your superlatives for when you need them!) star cluster of "quasar luminosity" ; the big stars die, forming lots (~10^5) of stellar mass black holes ; merge those rapidly (thanks t

  • He's good for these jobs.

  • Need more resolution.

  • 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"!"

    • With only successful 19 submissions accepted [slashdot.org] in your time on here, it looks as if you don't have anything better to do.

      Complained recently about the poor quality of articles on Slashdot?

      Well you know what to do about it. More often.

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