Today another graduate student has earned a doctoral degree in astronomy. Today's lucky winner is Fergal Mullally, an Irishman here at the University of Texas. Fergal, like myself, studies white dwarfs, the ashes of stars that have burned all of their nuclear fuel.
Fergal has spent the last several years looking for planets around white dwarfs. Due to complex physics that is not well understood, white dwarfs of very specific temperatures "pulsate," getting brighter and fainter as the atmosphere sloshes around. This sloshing is very steady, however, and is almost as steady as the most accurate atomic clocks on Earth.
If a pulsating white dwarfs has a planet around it, the planet's gravity will pull on the white dwarf, causing it to move in its own small orbit. Our sun slowly moves in such an orbit due to the pull of the planet Jupiter. As the white dwarf moves, sometimes it will be a little closer to us, and sometimes it will be a little further away. The light that it emits will then take either a little shorter or a little longer time to get to us. So, if we see the white dwarf's pulses arriving a little early or a little late, and this happens in a very regular fashion, there might be a planet there!
Fergal's results are very interesting. Most white dwarfs don't show any evidence of a planet, but one is very interesting. Fergal still needs a little more data to tell what's going on. And once he knows, I'll let you know.
So, congratulations, Fergal! Fergal will be leaving Texas this summer to take a job as a postdoctoral researcher at Princeton, helping out with some massive amounts of astronomical pictures they've been taking.