News Astronomy

A newly found world blurs the boundary between planet and moon

The find reopens an old fight over what makes a planet a planet

An illustration shows a glowing brown dwarf in the foreground, a Jupiter-sized object behind it and a star as a bright point beyond.

A newly spotted extrasolar object about the mass of Jupiter (illustrated in the middle) orbits a brown dwarf (foreground) which orbits a small star (bright point in the background). Astronomers aren’t sure what to call it.

M. Kornmesser/ESO

By Lisa Grossman

A newly discovered cosmic object is not a planet, not a moon — but a third thing we don’t have a name for yet.