V664 Cassiopeia is complicated. It consists of two stars that are so close together they’re almost touching. It’s ramming into clouds of gas and dust like a cosmic fist. And it’s leaving behind a trail of breadcrumbs that may span several light-years. The system is in Cassiopeia, the queen, which is low in the north-northeast at nightfall right now. V664 is to the left of the “W” formed by Cassiopeia’s brightest stars, although it’s too faint to see with the eye alone. But a telescope sees a remarkable sight — a structure that looks something like a jellyfish squirting across the sky, or perhaps a fist jabbing a pool of water. The system consists of a “dead” star known as a white dwarf, plus a second star that resembles the Sun. Not long ago, the white dwarf was also a “normal” star like the Sun. But it puffed up to giant proportions, engulfing its companion. As the companion swirled through the star’s outer layers, it stole some of the hot gas for its own, but kicked most of the gas a
