A Jupiter-mass planet has been discovered orbiting a white dwarf. That means the planet survived the death of its host star – when the star reached the end of its main sequence lifetime, expanded, and shed its outer layers:
On Wednesday in the journal Nature, astronomers reported observing a tantalizing preview of our solar system’s afterlife: a Jupiter-size planet orbiting a white dwarf some 6,500 light years from here.Astronomers Found a Planet That Survived Its Star’s Death, New York Times
Known as MOA-2010-BLG-477Lb, the planet occupies a comparable orbit to Jupiter. The discovery not only offers a glimpse into our cosmic future, it raises the possibility that any life on “survivor” worlds may endure the deaths of their stars.
Astronomers can’t actually see the white dwarf or the planet because they are too faint. This discovery was made using a technique called microlensing. The planet’s gravity acts like a lens and bends background light (this is the same effect as gravitational lensing, just on a smaller scale). Astronomers can estimate the mass of the planet and the white dwarf by studying the way the light is bent.