When the nuclear fusion that powers stars flickers out, most collapse and explode in a dramatic supernova. Now, astronomers have discovered a quieter fate for two pairs of stars. One in each couple was snuffed out after their vampire-like partner apparently drained off most of their mass.
Stars condense out of tenuous clouds of gas.
The protostellar cloud collapses around a dense core made mostly of hydrogen, heating it until the hydrogen nuclei begin to fuse and heat up the star. Often, a single cloud gives birth to several stars simultaneously and the newborns pair off in a gravitational orbital dance. The nearby companion can dramatically alter the fate of a smaller star. If the partners drift close enough, the gravitational pull of the more massive star will drag material off its neighbor. But because these extinguished stars have no internal power source, they don't shine brightly.