Results soon to be published in The Astrophysical Journal Letters, tested Einstein's theory of general relativity in a new way.

Two white dwarf stars are so close together that they make a complete orbit in less than 13 minutes, and they should gradually be slipping closer, according to general relativity. Gravitational waves, though not yet directly observed, should carry away energy causing the stars to inch closer together and orbit each other faster and faster.

Every six minutes the stars in J0651 eclipse each other as seen from Earth, which makes for an unparalleled and accurate clock some 3,000 light-years away. Compared to April 2011, when the researchers discovered this object, the eclipses now happen six seconds sooner than expected.

Artist's conception with ripples to demonstrate how the white dwarf pair emits gravitational waves. Credit: NASA

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