# If the sun becomes a black hole will its schwarzschild radius change?

1. Oct 23, 2014

### avito009

I know that the schwarzschild radius is proportional to the mass. But in case of black holes the mass remains the same only the size and density changes. So does the schwarzschild radius stay same when it is the sun and when it becomes a black hole?

2. Oct 24, 2014

### Matterwave

The Schwarzschild radius is not a physical radius, it's a calculated radius at which the event horizon would form if matter would be compressed to within that radius. So there's 2 ways you can answer this question. 1) Yes, the Schwarzschild radius, since it's just a calculated number, remains the same between the Sun now and the Sun if it were a black hole since the mass of the Sun is all that is necessary to determine it. 2) The Sun has no Schwarzschild radius since it is NOT a black hole. There is no event horizon associated with the Sun.

3. Oct 25, 2014

### SteamKing

Staff Emeritus
And in case you are still lying awake at night, worrying that the Sun might become a black hole, it is too small a star (It has insufficient mass) for that particular fate. After some spectacular end-of-life fireworks where it grows into a red giant, the sun will end its days as a white dwarf star, approximately the size of the earth. However, this white dwarf star will be much denser than the earth, since it will pack in much of the sun's mass into the smaller body.

http://en.wikipedia.org/wiki/Sun#After_core_hydrogen_exhaustion