MadSci Network: Astronomy

Re: When Energetic objects enter Black Hole,where does the energy go?

Date: Tue Sep 5 12:55:32 2000
Posted By: Angelle Tanner, Grad student, Astronomy, UCLA
Area of science: Astronomy
ID: 967342184.As

When material from a star falls into a black hole, it gets torn apart by
the immense gravitational forces exerted upon it. Some of the matter gets
converted into energy and is emitted by the black hole as X-rays (high
energy photons). This is why much of our observational evidence for 
stellar black holes is in the form of known X-ray binary systems like
Cygnus X-1 in which a normal star is orbiting around an unseen X-ray

There has been much debate on how to describe the properties of black holes
given that so little is known and can BE known about them observationally. 
Much of what is discussed involves understanding black holes in 
relation to General Relativity (how matter interacts with space and time)
and Quantum Mechanics (how matter behaves on small scales). Black holes
have three observable properties: mass, angular momentum (their rotation)
and charge (the amount of positive or negative particles they contain).
However, in an attempt to understand them better, Physicists like
Stephen Hawking applied the laws of thermodynamics to black holes. This
along with the idea of Hawking radiation in which a particle and its
anti-particle form spontaneously near a black hole and then one of them 
get sucked in while the other escapes lead Hawking
and others to claim that black holes do have a finite temperature which is
very, very near zero Kelvin. In general, it is assumed that only things
which give off radiation (like the Sun) can have a temperature so Hawking
radiation accounts for this. 

I am sure there are tons of books about black holes at your local bookstore
since the public has always been facinated with them. I would suggest
starting simple by looking at astronomy text books since the physics can
get quite complicated quite quickly. Good luck! 

[Moderator's note: The Usenet Relativity 
FAQ has some useful information about black holes and Hawking radiation.]

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