Tuesday, August 28, 2012

Even white dwarfs must obey Einstein

The white dwarfs are 1/3 the Earth-Moon distance apart
The Earth-Moon system (top) and binary white dwarf system (bottom) to scale.  Click to enlargify.  Earth (right) and Moon (little brown spec on left) images from NASA/JPL/Galileo; artwork by yours truly.
3,100 light-years away in the direction of the constellation Gemini lurks one of the most extreme pair of stars that we know about.  Two white dwarfs, the remains of ordinary stars similar to the sun, whirl around each other every 12 minutes and 45 seconds.  As they orbit, Einstein's theory of general relativity predicts that their gravity distorts space and time itself, and these distortions (called gravitational waves) carry away some energy from the system, forcing the two white dwarfs to draw ever nearer.  Locked by gravity in a slow death spiral, these white dwarfs are destined to collide and merge in two million years. At least that was the prediction, and today it was confirmed by an international team of astronomers (including many friends and colleagues of mine, though I wasn't involved).