New observations of a white dwarf prove Chandrasekhar’s model right using an experiment of his most bitter rival.
As it runs out of usable hydrogen to sustain it, the Sun will expand into a red giant for a time, and then what matter it has remaining will collapse into a white dwarf. And then what?
Yesterday I talked about the Higgs, and how its discovery has led to a flurry of articles about how it might apply to astrophysics. So today here’s another example, and this one’s interesting because it’s not simply trying to use the Higgs to explain known phenomena, it’s trying to use astronomical observations to understand things about the Higgs. It comes from a paper recently published in the Astrophysical Journal, and concerns the spectra of white dwarf stars.
Determining the age of galaxies and globular clusters can be a bit of a challenge. There are several ways you can get a handle on galactic age. One of these is by looking at the ratio of red dwarf stars to larger stars. Red dwarf stars burn very slowly, so their lifetimes can be 100 billion years or more. Given that the universe is only about 14 billion years old, this means that red dwarfs haven’t had time to die off. Larger stars die off faster, so the higher the proportion of red dwarf stars, the older the galaxy should be.
Novas occur when a white dwarf orbits with another star and captures some of the star’s outer material. This material forms an accretion disk around the white dwarf, which gradually falls to its surface. When material accumulates on the surface of the white dwarf, it can trigger a nuclear explosion that causes it to brighten similar to a supernova, but not nearly as intense. Since the explosion doesn’t destroy the star, it is possible for a nova to occur again after more material has accumulated.
When a star dies, there is a limit to how massive it can be, known as the Chandrasekhar limit.
There is a limit to how massive a white dwarf can be, known as the Chandrasekhar limit. While this limit is determined by properties of quantum theory, such as degeneracy pressure, the limit can be found using a simple stellar model.