Zhenwei Li

Be stars are rapidly rotating luminaries with bright gas disks. Usually, a companion star spins them up: mass flowing from the neighbor whirls the star like a bullet in a rifled barrel. But there are also lone Be stars without a partner: their origin long remained a mystery. New research shows that solitaries can be born from a supernova explosion.

Two spinning tops whirl so close they nearly touch. One is scorching blue, the other dim white. Together they complete a full orbit in twenty hours. This is the pair Feige 64: a blue star with a mass of just a third of the Sun's, and a white dwarf, the cooled core of a former star, one and a half times heavier than our Sun. The blue star seems too hot for its mass.