Depends how you define the boundry of the event itself, both in space and in time.
Stellar cores are relatively small, and the infalling matter is essentially in freefall at high g, gets to a significant fraction of c in about 0.1 seconds.
The visible disk of a red supergiant — of the kind that can supernova or surprise us by failing — is on the order of multiple AU radius, so speed of light limits there are in the tens of minutes.
Here's a short (12 page) and pretty easy article from The Astrophysical Journal (2003), about end of life for massive stars. And why some would "directly" collapse (no big & bright supernova) into black holes.
No, not if we've observed it. There are predicted historical events which can be shunted into the future by running away bravely, but if you've seen them happen, you can only change how long ago.
no, relativity allows for reference frames where the event hasn't happened yet, even though it has happened for you. there's no simultaneous "it has already happened" for all frames.
You basically let material stream into a black hole, it forms an acreation disk which gets very hot and dense even before the material actually falls into the black hole. The temperatture and pressure is high enough to trigger nucleosynthetic fusion reactions that generate heavy elements from lighter stuff, like the abundant hydrogen and helium. And a lot of "process heat" that can be used as energy source for other purposes. :)
Perhaps a superadvanced civilization training an AI model on all remaining negative entropy in their solar system so they can more effectively create realistic propaganda for the upcoming election on their now rather chilly mars colony.
They could have used a dense Dyson sphere to “suck” the energy of the star, but if that was the case we would be able to detect its infrared radiation.
https://en.wikipedia.org/wiki/Dyson_sphere
Anyway, I prefer the giant star eating dragon alternative ;-)
It's been a while since I crawled Wikipedia's rabbit hole on this - but I recall there being regions of the stellar "mass vs. metallicity" graph in which direct collapse to a black hole is the expected outcome.
not an astro anything, but the easy question is how does the sun switch off it's light output so suddenly as to cause a perfect garavitational collapse
presumably it has to be a large metal rich star and exist without too much local gas or a companion star
one thing is clear at this point is that the variety of stelar and galactic variability is much larger than what was predicted even a few decades ago, though the idea of a star just neatly removing itself from this universe when it's done, is very strange indeed
It doesn’t necessarily switch anything off or collapse - it’s possible for a star of the right mass and density to simply end up with a core that is held up only by degeneracy pressure, and the core slowly shrinks as it cools until it lies within its schwarzschild radius, and the rest of the star is either quietly consumed by this relatively slow process, or just escapes as though nothing much happened. Which from the outside looks like the star just turning off.
I assume they meant until all the mass collapses across the threshold, the remaining shell of the star outside is still radiating energy and a "solar" wind, which is particles escaping. So some is escaping away while some is slipping under.
Like people spent years of their life scientifically studying the problem and didn’t think of this before making the claim?
It was multi-wave analysis not just visible light, IR spread can differentiate this.
It’s been missing since 2015. Probability of something being large enough to cover the star and stay on a path completely obscuring it for 10 years is shall we say, not likely.
It didn’t rage against the dying of the light, it just switched off.
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