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posted by takyon on Tuesday May 30 2017, @11:00AM   Printer-friendly
from the there's-supposed-to-be-an-earth-shattering-kaboom dept.

There are a few known ways that black holes could be created. First way: start with a very massive star, watch it burn through all its nuclear fuel, and wait for the core to collapse in a violent supernova explosion, leaving a black hole behind. Second way: start with a neutron star, and let it accumulate enough mass to push it over the edge, either by accretion or by colliding with something like another neutron star. There was long theorised to be a third way: for a star to collapse directly into a black hole with no supernova. Astronomers using the Large Binocular Telescope, and the Hubble and Spitzer Space Telescopes have observed just such a thing happening to a star in the nearby galaxy NGC 6946, 22 million light years away. They saw a star of 25 solar masses, given the designation N6946-BH1, quietly wink out into a black hole.

Astronomers have watched as a massive, dying star was likely reborn as a black hole. It took the combined power of the Large Binocular Telescope (LBT), and NASA's Hubble and Spitzer space telescopes to go looking for remnants of the vanquished star, only to find that it disappeared out of sight.

It went out with a whimper instead of a bang.

The star, which was 25 times as massive as our sun, should have exploded in a very bright supernova. Instead, it fizzled out — and then left behind a black hole.

"Massive fails" like this one in a nearby galaxy could explain why astronomers rarely see supernovae from the most massive stars, said Christopher Kochanek, professor of astronomy at The Ohio State University and the Ohio Eminent Scholar in Observational Cosmology.

As many as 30 percent of such stars, it seems, may quietly collapse into black holes —no supernova required.

"The typical view is that a star can form a black hole only after it goes supernova," Kochanek explained. "If a star can fall short of a supernova and still make a black hole, that would help to explain why we don't see supernovae from the most massive stars."

He leads a team of astronomers who published their latest results in the Monthly Notices of the Royal Astronomical Society.

The original paper (paywalled) appears to be "The search for failed supernovae with the Large Binocular Telescope: confirmation of a disappearing star" (DOI: 10.1093/mnras/stx816) but it is not linked in the JPL press release. Also available as arXiv:1609.01283.


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  • (Score: 0) by Anonymous Coward on Tuesday May 30 2017, @12:45PM (4 children)

    by Anonymous Coward on Tuesday May 30 2017, @12:45PM (#517601)

    Different AC. So it just means they saw a star disappear (and are guessing it must have been turned into a black hole)? That is pretty creepy.

  • (Score: 1) by kurenai.tsubasa on Tuesday May 30 2017, @01:53PM (3 children)

    by kurenai.tsubasa (5227) on Tuesday May 30 2017, @01:53PM (#517630) Journal

    My guess is it doesn't take like a ton of guessing to arrive at “I guess it's a black hole.” I imagine you'd need to run the right equations with the estimated mass and composition of the star to verify that a black hole is what you're looking at instead of some other very-dense-but-not-quite-as-dense object like a neutron star. IANAAstronomer though so it's probably more involved than that.

    We can clearly see the accretion disk in the image series in TFA. Whatever was left behind appears to be very massive and very small. I admit, it's not quite Gargantua from Interstellar, but I'm going to conjecture that's just because it's just one solar mass instead of thousands. All we can really make out is the hot, bright gasses falling in; the event horizon itself is probably too small to be captured in an image of that resolution.

    I suppose it is a bit creepy. However, if there were a planet orbiting this star and that didn't get totally cooked by the star's former atmosphere around the black hole, I assume that it would happily continue orbiting the mass pretty much as it always did, with some adjustments to the orbit since the black hole is going to be less massive than the star was. It looks like that gas cloud has enough velocity to continue expanding away from the black hole.

    Anyway, moral of the story is, this is why it's a good idea to always start looking for a new giant fusion reactor when the warranty runs out on the one you're currently using! At least our giant fusion reactor still has a good few billion years left until the warranty's up.

    • (Score: 3, Informative) by butthurt on Tuesday May 30 2017, @04:31PM

      by butthurt (6141) on Tuesday May 30 2017, @04:31PM (#517733) Journal

      > it's just one solar mass

      The NASA page says "25 times as massive as our sun." If I recall, stars of less than ~3 solar masses aren't expected to form black holes.

    • (Score: 0) by Anonymous Coward on Tuesday May 30 2017, @04:47PM (1 child)

      by Anonymous Coward on Tuesday May 30 2017, @04:47PM (#517742)

      We can clearly see the accretion disk in the image series in TFA.

      What part of "(Artist's Concept)" do you not understand?