Just saw a BBC documentary called Space - Star Stuff.
They showed an experiment which purports to show what a supernova looks like as it blows (basically a small capsule containing the theorised material of a star about to blow which gets zapped with a really big laser, the resulting bang is filmed at ridiculously high speed).
In the explosion the shockwave expands outwards (looking very pretty I might add) up to a limit then it contracts.
Don’t remember the name of the lab, but it’s in New York and uses what the guy says is the largest laser in the world.
Is this normal for explosions? That is, why did it contract? Is it due to the experiment itself (maybe it wasn’t a vacuum, so ambient air was involved), or do all explosions expand then contract?
Looked just like a mandelbrot set though. Really neat.
Hmm… well, I can’t say about what they would have done to simulate the effect, but I think real star-sized supernovae would contract because of (a) an enormous gravitational pull and (b) the fact that they’re radiating heat and energy away into space like just about nothing else.
It sounds like the narrator was switching between results from the Relativistic Heavy Ion Collider at Brookhaven labs in NY, where they make quark gluon soup, and the the National Ignition Facility in Livermore, Ca, where they blast things with the most powerful lasers in the world.
well the filming was in one facility and the man in charge was Prof. Paul Drake (who is listed as being from U of Michigan and is referenced in several places on google, investigating supernova in the lab).
But all this aside, would supernova explosions contract? (Think of any movie of Nukes you may have seen. First air goes out, then gets sucked back in. That’s sort of what it looked like. Not quite, but close).
From what I’ve read, they implode and then explode. When the stellar core runs out of fuel, it undergoes gravitational collapse, since there is no longer any radiation pressure to support it. This collapse produces an outgoing shockwave and burst of neutrinos that causes fusion in the outer layers of the star. The imploding core has enough energy to create elements heavier than iron. It also blows off the outer layers of the star.
So he’s using the Nova laser (pix and info here) at the national ignition faciility in Livermore CA.
The first link talks about the supernova blast wave expanding outward until it hits, and compresses matter in the interstellar medium around the star. That results in a reflected blast wave which travels back towards the site of the supernova.
Incidentally, I am very impressed with Mr. Paul Drake. He’s really come up in the world since his early days as Perry Meson’s hired gumshoe.
Small world — one of my old GFs is currently doing graduate research under Paul Drake, and has in fact been in charge of doing data runs at the Omega laser at the University of Rochester.
As for “why does it contract?” the answer for natural supernovae is fairly simple: the heat energy pressure from the interior which is in the process of making post-carbon (oxygen, silicon, iron) elements distends the star. When it gets to the point where it’s producing iron, about half an hour before the supernova explosion begins, it’s reached the bottom of the curve of binding energy, and any further fusion absorbs rather than giving off energy. So the monstrously distended star no longer is producing the energy to keep it at the dimensions it had, much like a balloon being hit by pins from all directions at once, and it collapses. The collapse of course produces massive gravitational energy, resulting in a supernova explosion.
Presumably the manmade effect attempted to duplicate the conditions of the supernova, and would therefore have a collapse followed by an explosive effect built in as a part of the modeling. An astrophysicist would need to explain this further, but that’s the basis.
Hmm… Im not making myself clear I guess. I got the mechanics of how a supernova explodes, the question is related to the experiment they showed on the documentary I watched.
It was performed by Drake (but they didn’t mention the name of the facility, only that it was in Upstate NY).
In the footage of the actual experiment they show the explosion of the sample, it creates a shockwave expanding outwards in a sphere. Suddenly it ‘hits’ a wall of some form since it then contracts again (creating a very neat looking shell of matter by the way).
THink of it as a pulse. Wave goes out, then back.
What I wanted to know was related to how accurate a modeling this was. Specifically whether a real supernova would send a shockwave out which would then bounce back/contract/collapse or whatever, or whether the effect in the experiment was cauased because it wasn’t performed in a vacuum. That is, there was air that got pushed out then collapsed back inwards to the vacuum created in the explosion (which is what Ive read happens in a nuclear explosion in atmosphere).
by the way, when I say it hits a wall, I don’t mean it actually hits a wall, I mean that it stops expanding (again, almost a perfect sphere), before contracting.
There were no physical structures involved from what I could see.
