WASP-69, given the formal name Wouri by the International Astronomical Union in 2019, is a K-type star somewhat like our Sun but slightly smaller. The planet with the tail, however, is much different from anything in our own solar system.

That’s because WASP-69 b, named Makombé in 2019 to match its host star (Wouri and Makombé are both rivers in Cameroon), is a hot Jupiter. This class of planet is defined by two major factors: its size similarity to our own gas giant planets and its close-in orbit around its host star.

WASP-69 b certainly fits the bill: It is about 10 percent bigger than Jupiter — though only 30 percent its mass — and orbits its star at a distance just less than five percent the distance at which the Earth orbits the Sun. This means the exoplanet is constantly scorched by stellar radiation to a degree that would make even Mercury sweat.

WASP-69 b was the subject of considerable attention in the summer of 2022 when it became one of the first targets of the James Webb Space Telescope (JWST).

In new research published Jan. 9 in The Astrophysical Journal, a team led by astrophysicists at UCLA has revealed the planet’s atmosphere is escaping into space, creating a cometlike tail that stretches at least 350,000 miles (563,270 km).