For some time, astronomers have theorized that there is a connection between planetary mass and rotation. In the solar system, Jupiter and Saturn both rotate rapidly, completing a rotation in roughly ten hours, while accounting for a significant fraction of the solar system's rotational energy. Usin g the W.M. Keck Observatory on Maunakea, Hawai'i, a team of astronomers tested this predicted relationship by studying 32 gas giants and brown dwarfs in distant star systems—6 giant planets larger than Jupiter and 25 brown dwarf companions. ...read more read less