This artist concept depicts two white dwarfs called RX J0806.3+1527 (J0806), swirling closer together, traveling in excess of 1 million mph (1.6 million km/h). As their orbit gets smaller and smaller, leading up to a merger, the system should release more and more energy in gravitational waves. This particular pair might have the smallest orbit of any known binary system. They complete an orbit in 321.5 seconds - barely more than five minutes. Credit: GSFC/D.Berry