By Adam Hadhazy
updated 6:38 p.m. ET, Tues., March. 9, 2010

After a decade of mystery, astronomers have now shown that a pair of white dwarf stars spin around each other in just 5.4 minutes, making them the fastest-orbiting and tightest binary star system ever found, the researchers claim.

The record-setting stellar duo, known as HM Cancri or RX J0806.3+1527, offer challenges in explaining how such a system might form. The super-quick stars may also present a great future test-bed for detecting gravitational waves, which are elusive ripples in space-time.

Researchers say the stars in HM Cancri are so near to one another - about a quarter of the distance between the Earth and the moon - that they could not get much closer without smushing together.