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White Dwarf Binary Stars Make Merger Plans

In the J0651 binary system two white dwarf stars orbit each other in less than 13 minutes--and it's getting a little faster all the time. John Matson reports

Just like corporations, stars, too, can engage in mergers and acquisitions: a new study has identified a pair of white dwarf stars heading toward a merger.

White dwarfs are the hot, superdense remnants of spent stars. In a binary system called J0651, two white dwarfs circle each other very rapidly. The binary pairing completes an orbit in less than 13 minutes.

And that already rapid orbital dance is speeding up as the two white dwarfs spiral in on each other. Each year their orbital period shrinks by 0.3 milliseconds. That’s actually a pretty dramatic change on astronomical timescales.

In about a million years, the white dwarfs will get so close that the larger one will start to cannibalize its smaller companion. Before long, the two stars will likely become one. The study appears in the Astrophysical Journal Letters. [J.J. Hermes et al, Rapid Orbital Decay in the 12.75-minute Binary White Dwarf J0651+2844]

The tightly wound white dwarf binary should also be radiating gravitational waves—ripples in the fabric of space and time. But today’s gravitational wave detectors are not sensitive enough to detect them. That’s okay—astronomers have another million years, before things get really interesting, to build an instrument that’s up to the task.

—John Matson

[The above text is a transcript of this podcast.]

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