Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3

TL;DR

This paper reports the discovery of an Earth-sized exoplanet orbiting a nearby ultracool dwarf star, highlighting its potential for atmospheric characterization with JWST due to its favorable properties.

Contribution

The first detection of an Earth-sized planet around an ultracool dwarf star using the SPECULOOS project, expanding the known population of such planets.

Findings

Planet orbits its star every 17 hours

High irradiation makes it a prime target for JWST spectroscopy

Potential to analyze atmospheric composition with ten JWST observations

Abstract

Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely unexplored, and only one of them, TRAPPIST-1, has so far been found to host a transiting planetary system. In this context, we present the SPECULOOS project's detection of an Earth-sized planet in a 17 h orbit around an ultracool dwarf of M6.5 spectral type located 16.8 pc away. The planet's high irradiation (16 times that of Earth) combined with the infrared luminosity and Jupiter-like size of its host star make it one of the most promising rocky exoplanet targets for detailed emission spectroscopy characterization with JWST. Indeed, our sensitivity study shows that just ten secondary eclipse observations with the Mid-InfraRed Instrument/Low-Resolution Spectrometer on board JWST should provide strong constraints on its atmospheric composition and/or surface mineralogy.