Discovery of a Transiting Adolescent Sub-Neptune Exoplanet with K2

TL;DR

This paper reports the discovery of a young, adolescent sub-Neptune exoplanet around K2-284, providing a valuable benchmark for studying planetary evolution and atmospheric loss in early stages.

Contribution

It presents the first well-constrained age estimate of a young exoplanet host star with a transiting sub-Neptune, highlighting its significance for evolutionary studies.

Findings

Discovered a 2.8 R_earth sub-Neptune exoplanet around K2-284

Estimated star's age to be 120 Myr with 68% confidence interval 100-760 Myr

The planet's properties make it ideal for studying atmospheric photo-evaporation

Abstract

The role of stellar age in the measured properties and occurrence rates of exoplanets is not well understood. This is in part due to a paucity of known young planets and the uncertainties in age-dating for most exoplanet host stars. Exoplanets with well-constrained ages, particularly those which are young, are useful as benchmarks for studies aiming to constrain the evolutionary timescales relevant for planets. Such timescales may concern orbital migration, gravitational contraction, or atmospheric photo-evaporation, among other mechanisms. Here we report the discovery of an adolescent transiting sub-Neptune from K2 photometry of the low-mass star K2-284. From multiple age indicators we estimate the age of the star to be 120 Myr, with a 68% confidence interval of 100-760 Myr. The size of K2-284 b ($R_P$ = 2.8 $\pm$ 0.1 $R_\oplus$) combined with its youth make it an intriguing case study for photo-evaporation models, which predict enhanced atmospheric mass loss during early evolutionary stages.