SDSS 0922+2928 and SDSS 1102+2054 - Hot Stuff for Astronomers

"Study Finds Missing Link in How Stars Die"
Space.com (November 12, 2009)

"How stars end their lives depends on how massive they are.

"Large stars are thought to die in explosive fits and collapse into the densest objects in the universe — black holes and neutron stars. Small stars languish as dim objects called white dwarfs. But what happens to stars right on the border is not certain. Now astronomers have observed two peculiar white dwarfs that may represent the end point for these objects.

"White dwarfs can be about the size of Earth, but contain roughly the mass of the sun. They have already burned up most of their fuel and shine weakly by releasing heat. Most white dwarfs are made of compacted carbon and oxygen, with small amounts of a few other elements.

"The new observations found, for the first time, two white dwarfs that contained much more oxygen than carbon, perhaps representing the end stage for stars that are between seven and 10 times the mass of the sun — just under the mass threshold for neutron stars and black holes...."

The stars are called SDSS 0922+2928 and SDSS 1102+2054. You won't see them in Earth's sky: they're about 400 and 220 light-years away, respectively.

What's exciting about these two stars is that they're the first white dwarfs found, that have this particular chemistry. And may be as massive as a star can be and become a white dwarf.

The article gives a pretty good overview of how the stars fit into the study of stellar evolution - and why astronomers will be looking for neon in their atmospheres.

Almost-related post:

• "Betelgeuse is Shrinking: Earth at Grandstand Distance from Supernova?"
  (June 10, 2009)