Gliese 367

Lore & Background

Gliese 367 is a red dwarf star, smaller, cooler, and much fainter than the Sun. Its radius is 0.457 times that of the Sun, its effective temperature is 3522 K, and its luminosity is just 2.88% of the Sun's. Initial measurements from stellar isochrones suggested a young age of less than 60 million years, but its highly eccentric orbit around the Milky Way is unusual for a young star, possibly resulting from a gravitational encounter. A 2023 study based on spectroscopic observations found its age should be much higher; estimates from gyrochronology give an age in the range of 4.6 to 4.8 billion years, and rotation-age relations suggest a value of billions of years. The star is suspected to be a variable with an amplitude of 0.012 stellar magnitude and a period of 5.16 years. A stellar multiplicity survey in 2015 failed to detect any stellar companions.

The designation Gliese 367 comes from the Gliese Catalogue of Nearby Stars, where it was the 367th star listed in the first edition. In August 2022, the system was included among 20 systems to be named by the third NameExoWorlds project, and 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 endemic Chilean wildflowers.

The star was observed by TESS in February–March 2019, leading to its designation as an object of interest. By January 2021, radial velocity data suggested a short-period planet, confirmed by transit photometry by December 2021. A direct imaging study in 2022 found no additional planets or stellar companions beyond 5 AU. The discovery of two additional super-Earth-mass planets with periods of 11.5 and 34 days was published in 2023.

Reader's Guide

Gliese 367 holds significance as a nearby red dwarf hosting a compact planetary system, including Gliese 367 b, a sub-Earth with one of the shortest known orbital periods at just 7.7 hours. This planet receives over 500 times the radiation Earth gets from the Sun, with dayside temperatures around 1,500 °C, and is likely tidally locked. Its atmosphere would have boiled away, and its core is extremely dense, composed primarily of iron and nickel, similar to Mercury's core. The star's contested age—ranging from less than 60 million years to about 4.6–4.8 billion years—and its highly eccentric galactic orbit add to its scientific interest, suggesting a possible past gravitational encounter. The system's inclusion in the NameExoWorlds project and its naming after Chilean wildflowers highlight its cultural connection. The discovery of two additional super-Earth-mass planets in 2023 further establishes Gliese 367 as a valuable laboratory for studying close-in exoplanets and their formation, as well as stellar evolution and dynamics.