Astronomers discover a pair of stars with extremely short orbit; circle each other every 51 minutes

A team of astronomers, including researchers from the Massachusetts Institute of Technology (MIT), have discovered a stellar binary (a pair of stars) with an extremely short orbit, appearing to circle each other every 51 minutes.

The new system, dubbed ZTF J1813+4251, resides about 3,000 light years from Earth, in the constellation of Hercules.

The newly discovered system seems to be a cataclysmic variable - a rare class of binaries in which a star similar to our sun orbits tightly around a white dwarf. It occurs when the two stars draw close, over billions of years, causing the white dwarf to start accreting, or eating material away from its partner star.

ZTF J1813+4251 is a cataclysmic variable with the shortest orbit detected to date. The researchers concluded that the stars are currently in the transition phase and that the sun-like star has been circling and donating much of its hydrogen atmosphere to the voracious white dwarf.

In another 70 million years, the stars will migrate even closer together, with an ultrashort orbit reaching just 18 minutes, before they begin to expand and drift apart.

"This is a rare case where we caught one of these systems in the act of switching from hydrogen to helium accretion," says Kevin Burdge, a Pappalardo Fellow in MIT’s Department of Physics. 

ZTF J1813+4251 was discovered within a vast catalog of stars, observed by the Zwicky Transient Facility (ZTF), a survey that uses a custom-built wide-field camera attached to a telescope at the Palomar Observatory in California to take high-resolution pictures of wide swaths of the sky.

Using the W.M. Keck Observatory in Hawaii and the Gran Telescopio Canarias in Spain, the researchers further focused on the binary system. They found that the first object was likely a white dwarf, at 1/100th the size of the sun and about half its mass. The second object was a sun-like star near the end of its life, at a tenth the size and mass of the sun (about the size of Jupiter).

Burdge and colleagues report their discovery in the journal Nature.