Dead stars

[Ronnie67]

Question, what happens to a star under 1 solar mass when it dies, does it just cool down and become a dead planet, also can small stars turn into a solid sphere. Just wondering.

[JulianO]

Stars up to about 8 solar masses all end up as white dwarfs pretty much. They're basically glowing cinders, cooling down slowly. They take a long time to cool down though - billions of years, and shrink to around the size of the Earth.

[Ronnie67]

so it remains as a white dwarf, even after the billins of earth years, in that case I better keep my sandles on, dont want to burn my feet

[JulianO]

Well eventually it will cool down so much that it no longer shines, and become a black dwarf. However as the time taken to do this is longer than the age of the universe, there aren't any black dwarfs as yet.

[Ronnie67]

thanks for that Juliano

[ollypenrice]

Stars up to about 8 solar masses all end up as white dwarfs pretty much. They're basically glowing cinders, cooling down slowly. They take a long time to cool down though - billions of years, and shrink to around the size of the Earth.

I don't doubt that you are right but the Chandrasekhar limit is 1.6 solar masses and I thought that Neutron stars collapsed at over about three. Are your 8 solar masses the values for stars before they start to go into mass-loss after they leave the main sequence?

Olly.

[Ronnie67]

I though it was about 3 solar massas, but when Juliano mention 8, i though i was wrong, thats why i did not quiery his answer

[JulianO]

Up to about 8 solar masses, the death throws of the star tend to bring it down below the Chandrasekhar limit which as you say is somewhere around 1.5 solar masses. The late stages of its evolution such as the red giant phase are characterised by a large solar winds losing a lot of material, and there is usually the final expulsion of a planetary nebula, which all end up with a remnant that is less the the Chandrasekhar limit.

Having a brief look around, it seems even stars up to 10 solar masses may also leave white dwarfs, though again it depends exactly on what happens in their death throws. Having a close companion that steals material off you in the red giant phase for instance can alter things, as can the metalicity. So I guess there are no hard and fast rules, but above 8 solar masses is usually where people start talking about core collapse supernovas that can leave neutron stars.