A pair of white dwarfs race around each other every 374 seconds, creating a rhythmic X-ray beacon that could reveal powerful gravitational waves.

Every 6.2 minutes, two dead stars complete an entire orbit around each other.

The system, eRASSU J060839.5–704014, or eRASSU J0608, is so compact that material from one white dwarf appears to strike the other directly, producing a strong X-ray pulse on every orbit. Astronomers have now found that the orbit is also shrinking unusually fast, making the system a promising target for future gravitational wave observatories.