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01101001
2017-May-26, 01:13 PM
NASA Hubblesite: Collapsing Star Gives Birth to a Black Hole (http://hubblesite.org/news_release/news/2017-19)


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.

George
2017-May-26, 02:17 PM
I wonder what's going on inside to prevent the big explosion? Is there additional pressure (e.g. neutrino production) for more massive cores?

From my earliest experience with failed firecrackers, I advise no one to go near it for a while. :)

Hornblower
2017-May-26, 03:12 PM
If I am not mistaken, some astrophysicists were wondering just the opposite in the early days of supercomputer simulations of collapsing supermassive stars. They initially had trouble getting a supernova out of the simulation, which had just collapsed with a whimper into a neutron star or a black hole with no outward fireworks. Apparently some sort of spin-related condition is needed for a rebound that lights up the envelope. Maybe this one was not spinning. I will leave it to others who know more about the topic than I do to elaborate.

George
2017-May-26, 03:58 PM
If I am not mistaken, some astrophysicists were wondering just the opposite in the early days of supercomputer simulations of collapsing supermassive stars. They initially had trouble getting a supernova out of the simulation, which had just collapsed with a whimper into a neutron star or a black hole with no outward fireworks. Apparently some sort of spin-related condition is needed for a rebound that lights up the envelope. Maybe this one was not spinning. I will leave it to others who know more about the topic than I do to elaborate.
I kinda recall that as well. This (http://www.skyandtelescope.com/astronomy-news/exploding-stars-explained/) may be it. It's the work of J. Craig Wheeler, et. al., involving an acoustic shock wave as a trigger, I think.

publiusr
2017-May-26, 09:22 PM
For no reason--the phrase "live fast, die young" comes to mind--that and a Redd Foxx quote about burning the candle at both ends, in the middle, around the side and up the back!!!

Ken G
2017-May-27, 02:06 PM
NASA Hubblesite: Collapsing Star Gives Birth to a Black Hole (http://hubblesite.org/news_release/news/2017-19)

It has long been expected theoretically that very massive stars could collapse into black holes without making supernovae. So the only question that the observations are addressing is just how massive the star needs to be for this to happen. Given the difficulties in accurately simulating a supernova, and the long history of failure that purely theoretical simulations have suffered, I don't find it surprising at all that the mass (and other attributes of the star like rotation, magnetism, and composition) where there is not a supernova, requires observations to elaborate. To me, this is a useful datapoint in that effort, that is being sold to the popular media, as disingenuously as usual, as some kind of shock.

bknight
2017-May-27, 03:03 PM
It has long been expected theoretically that very massive stars could collapse into black holes without making supernovae. So the only question that the observations are addressing is just how massive the star needs to be for this to happen. Given the difficulties in accurately simulating a supernova, and the long history of failure that purely theoretical simulations have suffered, I don't find it surprising at all that the mass (and other attributes of the star like rotation, magnetism, and composition) where there is not a supernova, requires observations to elaborate. To me, this is a useful datapoint in that effort, that is being sold to the popular media, as disingenuously as usual, as some kind of shock.
Surely the think tanks have simulated stars with increasing size to determine a tipping point where it goes supernova.

Ken G
2017-May-27, 05:15 PM
Surely the think tanks have simulated stars with increasing size to determine a tipping point where it goes supernova.Certainly, but the question is, whether the simulations are correct or not, both in terms of what is a low enough mass that it will simply make a white dwarf, and what is a high enough mass that it will all just fall into a black hole, neither of which produces an explosion. As was mentioned above, most simulations don't explode at all, even starting with stars that have been observed to explode. So you can't put much predictive stock into the simulations! At the moment, supernova simulations are more like efforts to understand what we already know happens from observations, rather than anything predictive. Nevertheless, they do predict that it should be possible to simply fall into a black hole, and they predict this happens moreso at the higher mass end of things. Beyond that requires observations, and no one should be surprised by anything that gets observed given that state of affairs. Even so, there's always the lure to present one's own observations as some kind of sea change!