Wednesday, December 06, 2006

Black Hole Eats Big Star. Sounds Dirty But It's Not.

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NASA telescope sees Black Hole gulping remote star.

By Will Dunham

WASHINGTON (Reuters) - A giant Black Hole displaying horrifying table manners has been caught in the act of guzzling a star in a galaxy 4 billion light-years away, scientists using an orbiting NASA telescope said on Tuesday.

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This is too cool. The amount of energy and power it takes for a Black Hole to rip apart and swallow a star is unimaginable. Think of an elephant being ripped apart and sucked down into a tiny pinprick and you get the idea. That is probably not really even a close analogy but I like it all the same.

For the uninitiated, a Black Hole is the remnant of a collapsed star of a certain, large, size. After the star swells it then collapses on itself. A few things can happen.

One, it can grow to a Red Giant and then puff off its outer layer leaving a charred cinder called a Brown Dwarf. It may glow for a while as a White Dwarf but eventually it dies a slow death, like the campfire burning out but not of fire but of nuclear energy fading. The ejected gas is a mixture of elements called a Nebula. Eventually the Nebula will feed a new star's material. This is how the universe was built when Hydrogen stars coalesced and then exploded over billions of years, each time the Gravity caused Hydrogen atoms to fuse into ever more complex molecules. Eventually the stuff of life was the result. (Or God make the whole shebang in seven days, whatever.) The Brown Dwarf is like a very, very large Jupiter that barley emits energy or light. Many think that Brown Dwarf stars may be part of the dark matter we can't find in the universe, along with Black Holes and other Baryonic stuff.

Another possibility is that in a larger star, the star explodes in a Supernova and then what's left collapses back on itself and compresses so tight that the electron-proton pairs become pushed together to form Neutrons. The Neutrons are strong enough to resist further condensing so the result is called a Neutron Star. This is the heaviest mass object in the universe. From the NASA website: According to astronomer and author Frank Shu, "A sugar cube of Neutron Star stuff on Earth would weigh as much as all of humanity!" The reason the star goes Supernova is that in the Neutron state the outer layer "bounces" off the hard surface and shoots back outward. The only thing that stops the star from continuing to collapse is that the Neutron material is strong enough to resist it's own Gravity. The resulting object is a mere few miles wide but incredibly dense! Neutron Stars are sometimes called Pulsars when they spin because they emit an Electromagnetic emission in a regular pulse.

The final result is a Black Hole. Really massive stars collapse and because the core is so heavy it can't resist it's own Gravity. (No will power I guess.) The result is that the matter continues to fall in on itself until everything is sucked into what's called a Singularity. A Singularity is a point in space where Gravity is infinite and the point has zero volume. And weird crap happens. Like the Gravity is so strong that light can't even go fast enough to escape so it is trapped in to an endless revolution around the Black Hole. Pretty much breaking the established laws of physics that light is the speed limit of the universe. The Black Hole is the end point of a star's life but also can be seen as an endpoint to reality as we know it to exist in our "normal" functioning universe. That's why the Black Hole is a wired object. It is something that is so small and dense it can't exist in our universe, yet, there it is! Contrary to popular belief, a Black Hole doesn't suck thinks into it. You can safely revolve around a Black Hole forever if you are far enough away. The point of no return is the Event Horizon or the radius from the center (if we could find the damn center since it is of zero volume!) called the Schwartzschild Radius. At this point the escape velocity is the speed of light and since nothing goes faster than light, well...

OK, so that's weird, right. Here’s the weirdest thing. Einstein's General Theory of Relativity predicted Black Holes and by God there they are. But since Time and Space are all dimensions affected by Gravity, a Black Hole will also cause time to slow down to a stop. In fact, any Gravity field will cause time to slow by a small amount but it takes a super-massive one to make time slow down significantly. Go live in the orbit of a Black Hole and you can watch the universe speed up around you. Since Einstein said we can't distinguish between a Gravity field and an accelerating object, the faster you go, time also will slow down until you get to the impossible-to-attain, speed of light. So in essence, photons, the carriers of the EM force (which light is a part of) have no sense of time since they are always flying around at the speed of themselves. Photons are not affected by time. Since they are massless, they can do that. To speed even a pebble of sand to the speed of light the mass would increase (to make up for time and space dilation) and the pebble would become infinitely massive and require infinite energy to push. Not happening anytime soon.

As related to this story above, a star that finds itself on a trajectory towards a Black Hole will eventually become trapped by the Black Hole's Gravity. It will become ripped apart literally from one end to the other and then if on an angular path, the resulting gas will accrete in a disk and become "swallowed" by the Black Hole. We can see this happening because as the "stuff" of the star breaks apart and speeds up in the gravitational pull it gets heated and emits energy in the X-Ray and Gamma-Ray spectrum of the EM scale. This is obviously before it crosses the event horizon where nothing can escape. Just like in a good detective story or piece of abstract art, it is what is not there that defines a Black Hole rather than what is there. But we know it is there from its effect on matter or how things act within its gravitational pull around it.


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