2006-10-20 16:18:48 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
A star is a big mass of gas. It originated as a hydrogen cloud that started contracting because gravity pulled it together. When this happens the interior gets denser and hotter. Dense enough and hot enough for fusion reactions to start. The latter produce heat and light that pushes outwards.
The result is an equilibrium between gravity and the light radiation. The star stabilizes and stays stable for billions of years. The sun is in this stage.
However, when the hydrogen is burnt up, the outward pressure is taken away and gravity takes over again. If the mass of this burnt out star is big enough, then there is nothing to counteract gravity.
The mass of the star will be more and more concentrated in a smaller and small volume. Gravity at the surface will become so strong that not even light can escape from it.
That is a black hole.
2006-10-23 16:07:46 · answer #1 · answered by cordefr 7 · 1⤊ 0⤋
It's a gravitational singularity.
The mass has been so condensed that there is a gravitational boundary around such an object that prevents even light, which is massless, from escaping.
2006-10-23 17:45:56 · answer #2 · answered by arbiter007 6 · 0⤊ 0⤋