Searching for Terrestrial Planets Orbiting in the Habitable Zone of Ultra-Cool Stars and Brown Dwarfs

TL;DR

This paper proposes using Kepler in 2-wheel mode to search for Earth-sized planets in the habitable zones of ultra-cool stars and brown dwarfs, aiming to find potentially habitable exoplanets with detectable atmospheric features.

Contribution

It introduces a novel survey strategy targeting ultra-cool stars and brown dwarfs with Kepler 2-wheel mode, focusing on detecting transiting Earth-sized planets in their habitable zones.

Findings

Expected to detect at least one transiting Earth-sized planet.

Targets are bright in infrared, enabling follow-up atmospheric studies.

Survey duration and target sample are optimized for success.

Abstract

We propose to use Kepler in 2-wheel mode to conduct a detailed search for Earth-sized planets orbiting ultra-cool stars and brown dwarfs (spectral types from M7 to L3). This population of objects presents several advantages for exoplanet surveys. First, ultra-cool stars and brown dwarfs are small and thus result in favorable planet-to-star area ratios. Second, because of their low effective temperature, the inner edge of their habitable zone is extremely close (2 to 3 days only). Third, our targets are bright at infrared wavelengths, which will enable detailed follow-up studies. Our program therefore represents a unique opportunity to find a transiting Earth-size exoplanet for which atmospheric features (including biosignatures) could be detected with near-to-come facilities such as JWST. Such exoplanet has not been discovered yet. Kepler in 2-wheel mode provides the required stability and photometric precision to make this survey successful. Our initial target sample includes 60 ultra-cool stars and brown dwarfs from which we expect to detect at least one transiting planet. We propose to monitor each source for 4 days, resulting in a total program duration of ~240 days.