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knotmeister
2008-Aug-29, 04:22 AM
Does a black hole have a surface like the sun? Or does it have a density gradient density like perhaps a gas giant?

Torg
2008-Aug-29, 04:29 AM
A black hole just has a mathematically defined distance from its center, the schwartzchild radius or event horizon. This is the radius from its center at which light can no longer escape. The only other point in it worth mentioning is its very center. It has no surface in the sense you are talking about, unless there is truly weird physics we do not know of going on inside the event horizon, or unless i am mistaken :whistle:.

mugaliens
2008-Sep-01, 01:27 PM
A black hole just has a mathematically defined distance from its center, the schwartzchild radius or event horizon. This is the radius from its center at which light can no longer escape. The only other point in it worth mentioning is its very center. It has no surface in the sense you are talking about, unless there is truly weird physics we do not know of going on inside the event horizon, or unless i am mistaken :whistle:.

The Schwarzschild radius is the radius where, if the mass were compressed to fit within that radius, it would collapse into a gravitational singularity.

The formula is simple: r=2Gm/c2

Because of their nuclear density, neutron stars typically form stellar black holes if they're about 3 solar masses or more.

Supermassive black holes, on the other hand, are formed from ordinary (non-neutron densities) and require approximately 150 M solar masses before that matter will collapse (condense) beyond it's Schwarzschild radius. Our galaxy's black hole, 3.7 M solar masses, is thought to have begun life as a stellar black hole.

For non-rotating BHs, the Schwarzschild radius is equivalent to the event horizon. For rotating BHs, it's close, but there is a slight difference.