02-26-2012, 02:04 PM
Much of the white-dwarf star is in time/space and far apart, due to being an explosive remnant. Further apart in time/space means closer together in space/time, hence the relatively high-density for its size (and low luninosity). The density of that stellar material is a million times more than the density of water, or like having the mass of the sun at the size of the Earth.