FORT DAVIS, Texas —Astronomers at The University of Texas at Austin’s McDonald Observatory and the Smithsonian Astrophysical Observatory have discovered a pair of burnt-out stars spiraling into one another at breakneck speeds. Orbiting each other in just 13 minutes, they will merge and possibly explode as a supernova in about 900,000 years. By watching them over time, scientists will test both Einstein’s theory of general relativity and the origin of some peculiar supernovae.