Yesterday, University of Texas grad student Elizabeth Jeffery successfully defended her doctoral dissertation, becoming the newest PhD astronomer. Congratulations, Elizabeth!
Dr. Jeffery's thesis is on white dwarfs in open star clusters. She has been using white dwarfs to get the ages of star clusters, and comparing that number to the ages of the same star clusters that astronomers get using other methods. The idea here is that the physics behind how we get the ages of white dwarf stars is different than the physics behind the ages of normal stars. White dwarf stars are slowly cooling and fading, so we use the physics of heat loss to get their ages. Normal stars shine by using nuclear fusion, so we have to use nuclear physics to get their ages. And, in both cases, other things are important, like the structure of the stars and how energy gets from the core of the star to the star's surface. In both cases, the physics are different, and there is a fair amount of room for error. Thankfully, though, Elizabeth finds that the ages agree over the range that she studied: the star clusters with ages of a few hundred million years to several billion years. That's a big time span, and it also covers a lot of different physics tests in both normal stars and white dwarf stars. It was a lot of work, and there is more remaining to be done to tidy up the results for publication, but it is very impressive and quite important.
Elizabeth is now preparing to move to the Space Telescope Science Institute in Baltimore, MD, where she will be a postdoctoral researcher there. Congratulations again, Elizabeth, and best wishes on your future career!