View Full Version : Seven types of compact stars?

2011-Dec-05, 05:54 PM
Perhaps zero class m stars have exhausted their nuclear fuel, but in the far future, fewer of them will still be main sequence. It is though that they do not become red giants, but just cool off, becoming more dense, mostly helium, not much larger than Jupiter. Some of the brown dwarfs, mostly hydrogen, have likely cooled to zero c = 32 f or colder, and shrunk significantly, so they are a second type of compact star. The still hot brown dwarfs are thought to have a density over 100 times that of water, so they might be considered compact stars plus the three regulars makes six and possibly Quark stars makes seven? Neil

2011-Dec-05, 11:55 PM
AFAIK, the compact stars are: white dwarf, neutron star, black hole. The density of a white dwarf is about a million times the density of water. That's what I call compact! IIRC, both white dwarfs and neutron stars have upper mass limits, beyond which they are unstable. Quark stars are, as yet, hypothetical.