Geoffrey Mo

A pair of white dwarfs whirls in a deadly dance: one star steals helium from its neighbor, spinning up a glowing disk. The orbit shrinks, energy leaves as gravitational waves. The rate of approach has been measured — the future LISA detector will catch the signal in four years.

Normally, black holes rip stars apart in the centers of galaxies. A new discovery shows that some black holes lurk in the outskirts. Astronomers spotted a flare tens of thousands of light-years from the center of a large galaxy. A computer algorithm trained on similar events helped identify it. Soon