My biology class is working on a project where we have to write a paper on how scientists know the stuff they do about our topic. I choose Black Holes as my topic, and I now need a bit of help. The points I have to address in my paper are:

1) a brief summary of what a black hole is,

2) some important names that are connected to black hole research,

3) how do they find black holes,

and 4) how do they know about the parts of a black hole (ex. the event horizon, the apparent horizon, ect.).

 

I already have plenty of information on the first point, but I could use some help with the last 3. If you could also include the source from which you receved the information, that would be greatly appreciated. Thanks for any help.

Link to Wikipedia: http://en.wikipedia.org/wiki/Black_hole

 

Also Google is a good search engine You can use.

1a) The Einstein Equations are the basic equations in General Relativity. They´re very complex diferential equations and there´s no know general solution to them.

1b) The first analytic solution found was that for a spherical symmetric mass distribution - The Schwarzschild solution. Even though "spherical symmetric mass distribution" might sound like a strong restrictment it´s quite usefull as planets and suns can be considered spherical symmetric to a good approximation. As a sidenote: The Schwarzschild solution is only valid outside the mass distribution.

1c) The Schwarzschild solution has a certain area where the coordinates are not defined. Since this area lies inside the mass distribution for suns or planets noone initially paid much attention to it.

1d) Someone (I think it was Chandraseka) was able to show that suns that run out of fuel will collapse to being so small that this "undefined area" lies outside the mass distribution if their mass exceeds the Chandraseka mass. That´s what you´d call a Black Hole: A spherical symmetric mass distribution with it´s undefined area (which is enlosed by the Event Horizont) outside of the mass distribution.

2) Einstein (General Relativity), Schwarzschild (1st analytic solution), Chandraseka (showing that suns will collapse beyond the event horizont), Kruskal/Penrose (there´s a coordinate that´s called "Kruskal Koordinates" or "Penrose Coordinates" that´s able to map the area within the Event Horizont. Can´t really tell those people´s contributions to it, though).

3) None has been directly observed, afaik. Methods would include looking for "jets" that are emitted by them, observing the movement of suns to find centers of gravity where no mass can be seen and perhaps light deviation.

4) Not completely sure what you mean with that question. The event horizont is just the surface that seperates the area where the Schwarzschild-coordiantes are defined from that where they aren´t (or at least where they don´t make much sense).

Sources: That was off my head. I´m neither interested in experimental physics nor in history of physics too much, but I hope that still helped you.

Yeah, it does help me. Thanks.