Gliese 367 b

Lore & Background

Gliese 367 b was among 20 systems named by the third NameExoWorlds project, with approved names announced in June 2023. The planet is named Tahay, and its host star is named Añañuca, after Chilean wildflowers. The name Tahay alludes to the bloom duration of Calydorea xiphioides, which flowers for only 7 to 8 hours each year, mirroring the planet's short orbital period.

Due to its extremely close orbit, the planet receives over 500 times more radiation than Earth receives from the Sun, resulting in dayside temperatures around 1728 K. The planet is presumably tidally locked, and any atmosphere it may have had would have boiled away. Observations from the James Webb Space Telescope indicate that the planet lacks an atmosphere and has a low albedo, with no day–night heat recirculation suggesting significant volatile loss.

The planet's core is likely composed of iron and nickel, similar to Mercury's core, and is extremely dense, making up about 91% of the planet's mass. The overall density is about twice that of Earth. The planet may have been stripped of its outer silicate layers due to collisions or evaporation by extreme stellar radiation.

Reader's Guide

Gliese 367 b holds significance as the smallest exoplanet within 10 parsecs of the Solar System that has a measured radius, though Proxima Centauri d and the planets of Barnard's Star are less massive and could be smaller. Its exceptional density raises intriguing hypotheses about its origin, including mantle evaporation or Mercury-like collisions. The discovery prompts broader inquiries into the habitability of small rocky planets orbiting M dwarfs and offers insights into planetary formation and atmospheric dynamics. The planet's extreme environment—with a 7.7-hour orbit, tidally locked state, and lack of atmosphere—provides a natural laboratory for studying the effects of intense stellar radiation on planetary surfaces and interiors. Its iron-rich core, making up the vast majority of its mass, challenges models of planetary composition and evolution, suggesting that such planets may be common around red dwarfs. The James Webb Space Telescope observations confirming the absence of an atmosphere and low albedo further constrain theories of volatile loss and surface processes on close-in exoplanets.

Did You Know?

• Gliese 367 b orbits its star in just 7.7 hours, one of the shortest orbital periods of any known planet.
• The planet's dayside temperature is around 1728 K.
• Its core is composed of iron and nickel, making up about 91% of the planet's mass.
• The planet is named Tahay after a Chilean wildflower that blooms for only 7 to 8 hours each year.

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