They find a ‘cataclysmic’ pair of stars with the smallest orbit ever seen

The stars are revolving around each other every 51 minutes. This dance is fatal: one is “eating” the other.


Half of the stars in our galaxy are solitary, like the Sun , and the other half are stars that form star systems that rotate in pairs or in groups, some with orbits so narrow that they could fit between the Earth and the Moon.

Now, a team led by the Massachusetts Institute of Technology (MIT) has discovered a stellar binary (a pair of stars ) with an extremely short orbit: they revolve around each other every 51 minutes.

The newly discovered system, which the team has named ZTF J1813+4251 , has the shortest orbit detected to date.

An unprecedented find

The finding, published this Wednesday in the journal Nature , has been made in collaboration with Harvard University and the Smithsonian Center for Astrophysics, among other institutions.

The system appears to be one of a rare class of binaries called “cataclysmic variables,” in which a Sun-like star orbits a white dwarf (the hot, dense core that remains of a star after it has exhausted its fuel).

These cataclysmic variables arise when, in a process that lasts billions of years, the two stars approach each other, causing the white dwarf to start accreting (eating) material from its companion star.

Astronomers captured this cataclysmic variable as the stars eclipsed each other, helping to accurately measure its properties.

Using the measurements, they ran simulations of what the system is likely doing today and how it should evolve in the next few hundred million years.

According to their calculations, both stars are in transition and the Sun-like star has been spinning around and “donating” much of its hydrogen atmosphere to the ravenous white dwarf.

Over time, the Sun-like star will shrink to a mostly dense, helium-rich core. And in 70 million years, the two will get even closer together, down to an 18-minute ultrashort orbit, before they start expanding and moving apart.