Star Falls Into Black Hole 169
thodelu writes with news that astronomers recently got a look at what they believe is a star falling into a black hole. Phil Plait explains:
"As the star approached this bottomless pit, the side of the star facing the black hole was pulled far harder than the other side of the star, which may have been a million or more kilometers farther away from the black hole. This change in pull stretched the star — this stretching is called a 'tide,' and is essentially the same thing that causes tides on the Earth from the Moon’s gravity and when the star wandered too close to the black hole, the strength of that pull became irresistible, overcoming the star’s own internal gravity. In a flash, the star was torn apart, and octillions of tons of ionized gas burst outward! This material whipped around the black hole, forming a disk of plasma called an accretion disk. Magnetic fields, friction, and turbulence superheated the plasma, and also focused twin beams of matter and energy which blasted out from the poles of the disk, away from the black hole itself. The energy stored in these beams is incredible, crushing our imagination into dust: for a time, they shone with the light of a trillion Suns!"
Re:Gravity... (Score:5, Informative)
Re:How long does this process take? (Score:4, Informative)
I wish I could edit my post. The follow up article has much more information.
There was some (not much though) light that could have been visible:
from our distance of nearly four billion light years, the flash of light was only bright enough to see with big telescopes.
As for the duration:
And this event is not over. As the material whirls around the black hole, turbulence and other forces inside the disk can cause the brightness to change. There have been several flares, and while it had been fading for a few days, suddenly on April 3rd the overall brightness increased by a factor of five!
Re:Silly question: (Score:2, Informative)
carved information on it that could be read from a distance, and slung it past the EH, how long would it remain visible?
It wouldn't be visible once it passed the event horizon. That's the defining characteristic of a black hole's event horizon: nothing escapes, including light.
Re:Silly question: (Score:5, Informative)
NO, absolutely not. An outside observer sees time "slow down" for objects that are approaching a black hole, so that each falling object approaches the event horizon asymptotically BUT NEVER ACTUALLY REACHES IT.
If you watched somebody falling into a black hole, and you kept a telescope trained on his wristwatch, you would see the second hand sweep slower and slower as he got closer to the EH distance. No matter how long your wait, you'll never actually see anything cross the EH from the outside.
(I am not kidding, this is what actually would happen. If this seems unpossible, don't worry too much--unless you've already studied special relativity and grasped at least that much, this is pretty counter-intuitive.)
Re:Silly question: (Score:5, Informative)
No he wouldn't. He looks back and sees the stationary guy 1000km away, but the light took a certain amount of time to get to him, negating any possibility of seeing the "future". The further out into the universe he looks, the further back in time he looks -- the same as happens to us when we stare really far into the sky from Earth -- if we're looking at something 1000 light years away, we know that it happened 1000 years ago (or more, if something managed to slow down the light for part of the journey). We can NEVER see the future (or for that matter, the present). Even reading this on your screen is old news by a tiny fraction of a second as the light moves from your screen to your eye.
Basically from the moving observer's perspective, nothing unusual is happening at all until the tidal forces kick in.
As he gets closer and closer to the singularity the tidal forces would rip him into atoms, then the atoms get ripped apart layer by layer until you end up with individual quarks (and who knows what it means to rip a quark or an electron apart.. ie: what happens when space is so warped that a signal can't make it from one side of a quark to the other without exceeding c.)
All that said, the stationary observer would NOT see the moving guy forever. As others have noted, along with seeing him slow down indefinitely, we'd also see him redshift indefinitely. Eventually he'd be so redshifted that he'd no longer be detectable by the instruments of the stationary observer. He'd still "be there" but could no longer be seen. A more sensitive instrument could see him for a longer period of time, but he'd still fade out eventually as all instruments no matter how good will have a finite cutoff for what they can detect.