Spin separates giant planets from ‘failed stars’

Clearest evidence yet that giant planets spin faster than their cosmic lookalikes For decades, astronomers have struggled to differentiate giant planets from brown dwarfs, a class of objects more massive than planets but too small to ignite nuclear fusion like true stars. Through a telescope, these cosmic lookalikes can have overlapping brightness, temperatures and even atmospheric fingerprints. The striking similarity leaves astronomers unsure if they have observed an oversized planet or an...