Artist's conception of the newly discovered planet MOA-2007-BLG-192Lb orbiting a brown-dwarf "star" that's only 6 percent as massive as our sun. Theory suggests that the three-Earth-mass planet is made primarily of rock and ice. Observational and theoretical studies of brown dwarfs reveal that they have a magenta color due to absorption by elements such as sodium and potassium in their atmospheres.
There's a new extrasolar planet on the block: a mini-orb likely covered with a deep ocean. And it takes the record for the lowest-mass exoplanet to orbit a normal star, astrophysicists announced Monday. The li'l planet — weighing in at three times Earth's mass — grabs the lightweight title from a five-Earth-mass planet just announced in April. The super-Earth is called MOA-2007-BLG-192Lb, after its host star MOA-2007-BLG-192L, which is located about 3,000 light-years from Earth. (A light-year is the distance light travels in one year, or about 5.88 trillion miles — 9.46 trillion kilometers.)