A planet orbiting a white dwarf

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.

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 Found a Planet That Survived Its Star’s Death, New York Times

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.

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