- (astronomy) an astronomical object with enough mass to achieve hydrostatic equilibrium, but not enough to initiate core fusion at any time in its existence. That is, it is rounded in shape and is smaller than a star. Planemos include planets, dwarf planets, and the larger moons of the Solar System, but also sub-brown dwarfs and rogue planets between the stars.
Contraction of planetary-mass object. Coined by Gibor Basri, Professor of Astronomy at the University of California, Berkeley, (UCB) at the 2003 IAU conference.