Gliese 367

A red dwarf star, Gliese 367 is smaller, cooler, and much fainter than the Sun. It has 0.457 times the Sun's radius, an effective temperature of 3522 K, and a luminosity just 2.88% that of the Sun.^[3]

Initial measurements from stellar isochrones suggested a young age of less than 60 million years old, but its orbit around the Milky Way is highly eccentric, unusual for a young star.^[8] It may have been forced into such an orbit via a gravitational encounter.^[8] However, a 2023 study, based on spectroscopic observations, found that its age should be much higher. Estimates from gyrochronology give an age in the range of 4.6 to 4.8 billion years.^[4]: 6 Rotation-age relations suggest a value of 7.95±1.31 billion years.^[5]

It is suspected to be a variable with amplitude 0.012 stellar magnitude and period 5.16 years.^[9] A stellar multiplicity survey in 2015 failed to detect any stellar companions to Gliese 367.^[10]

The designation Gliese 367 comes from the Gliese Catalogue of Nearby Stars. This was the 367th star listed in the first edition of the catalogue.

In August 2022, this planetary system was included among 20 systems to be named by the third NameExoWorlds project.^[11] The approved names, proposed by a team from Chile, were announced in June 2023. Gliese 367 is named Añañuca and its innermost planet is named Tahay, after names for the endemic Chilean wildflowers Phycella cyrtanthoides and Calydorea xiphioides.^[7]

The star Gliese 367 was observed by TESS in February-March 2019, leading to its designation as an object of interest,^[3] and by January 2021 additional radial velocity data suggested the existence of a short-period planet, albeit with low certainty.^[12] The planet's existence was confirmed by both ground-based and satellite-based transit photometry data by December 2021.^[3]

Gliese 367 b is a close-orbiting sub-Earth that takes just 7.7 hours to orbit its star, one of the shortest orbits of any planet. Due to its close orbit, the exoplanet gets bombarded with radiation over 500 times what Earth receives from the Sun.^[3][13] Dayside temperatures on GJ 367b are around 1,500 °C (1,770 K; 2,730 °F).^[14] Due to its close orbit, it most likely is tidally locked.^[15] The atmosphere of Gliese 367 b, due to the extreme temperatures, would have boiled away along with signs of life.^[14] The core of GJ 367b is likely composed of iron and nickel, making its core similar to Mercury's core. The core of GJ 367b is extremely dense, making up most of the planet's mass.^[14]

A direct imaging study in 2022 failed to find any additional planets or stellar companions around Gliese 367. This rules out any companions at distances greater than 5 AU with masses greater than 20 M_J (for an age of 5 billion years).^[8] The discovery of two additional super-Earth-mass planets with periods of 11.5 and 34 days was published in 2023.^[4]

• List of nearest exoplanets