Many of the stars in the Milky Way galaxy are small, dim red dwarfs—stars much smaller than the sun in both size and mass. TOI-6894, located far away from Earth, is one of them.

Astronomers previously thought a star like this could not have large planets circulating it, because its mass is only about 20 percent of the sun, meaning its planetary system—generated from materials surrounding the star—would not have contained enough mass to form a giant body like Saturn or Jupiter.

But when observing TOI-6894, an international research team detected a clear transit signal—a temporary decrease in a star’s brightness caused by a planet passing across it. This newly discovered planet, named TOI-6894b, blocks 17 percent of the star’s light, indicating the planet is fairly large. The signal was picked up by the Transiting Exoplanet Survey Satellite (TESS), an observation instrument launched by NASA to hunt for planets orbiting stars outside of our solar system.

This makes TOI-6894 “the lowest mass star known to date to host such a planet,” said Edward Bryant, Astrophysics Prize Fellow at the University of Warwick, in a press statement. The finding appears to upend conventional theory on how planets are formed. “This discovery will be a cornerstone for understanding the extremes of giant planet formation,” Bryant said.

Astronomers at University College London and the University of Warwick, as part of a global collaboration with partners in Chile, the US, and Europe, trawled through the data of about 91,000 red dwarf stars observed by TESS before discovering the planet TOI-6894b. After that, the nature of TOI-6894b was clarified by additional observat...