K2-332 b

Lore & Background

K2-332 b was detected via the transit method, with an average transit duration of 2 hours and 2 minutes and a transit depth of 0.6508%. Its host star, K2-332, is a dim red dwarf with about 20% the mass and size of the Sun. The planet's radius of 2.2 Earths and estimated mass of 5.47 Earths yield a density consistent with a watery or gaseous Mini-Neptune rather than a rocky Super-Earth. Its equilibrium temperature of 266 K is somewhat higher than Earth's, and it orbits within the inner part of the habitable zone, about one-third of the way between the runaway greenhouse limit for Super-Earths and the absolute inner edge. The planet is likely tidally locked due to its close orbit and low eccentricity, with one side permanently facing the star.

Reader's Guide

K2-332 b's significance lies in its potential habitability despite its low density. While a solid surface is typically considered necessary for life to develop spontaneously, studies from 2021 indicate that sub-Neptunes can harbor abundant water and life-friendly molecules such as nitrogen, oxygen, and CO₂ in their atmospheres, with stable habitable temperatures and pressures. If the system contains a leftover dust disk or asteroid/comet belt, panspermia from a terrestrial planet or Earthlike moon could introduce microbial life, which might have enough time to reproduce before succumbing to harsh conditions. Tidal locking would create a hot dayside and cold nightside, but oceanic currents and wind could distribute heat, potentially warming the nightside past the freezing point of the atmosphere and cooling the dayside below 100°C. Under such conditions, the habitable region could extend to 55° in both hemispheres on the dayside and around the nightside near the equator, with a maximum temperature of about 42°F. Higher carbon dioxide levels could expand this zone across most of the planet, excluding the nadir and high polar regions. These findings, supported by 2019 studies of the TOI-270 system, suggest that Mini-Neptunes like K2-332 b may possess life-friendly atmospheres rich in organic matter.

Did You Know?

• K2-332 b receives 1.17 times the light Earth gets from the Sun.
• Its equilibrium temperature is 266 K, somewhat higher than Earth's.
• The planet has an estimated mass of 5.47 Earths and a radius of 2.2 Earths.
• It was discovered by the K2 'Second Light' mission in 2016.