A Second Earth-Sized Planet in the Habitable Zone of the M Dwarf, TOI-700

TL;DR

This paper reports the discovery and validation of TOI-700 e, a second Earth-sized planet in the habitable zone of a nearby M dwarf, using TESS data and follow-up observations, highlighting its potential for future atmospheric studies.

Contribution

The paper presents the identification and validation of a new Earth-sized planet in the habitable zone of TOI-700, expanding known planets in this system with detailed analysis from TESS data.

Findings

TOI-700 e is a 0.95 R$_ ext{Earth}$ planet in the habitable zone.

The system now hosts four planets, including two in the habitable zone.

The discovery was enabled by multi-sector TESS observations and follow-up validation.

Abstract

We report the discovery of TOI-700 e, a 0.95 R$_\oplus$ planet residing in the Optimistic Habitable Zone (HZ) of its host star. This discovery was enabled by multiple years of monitoring from NASA's Transiting Exoplanet Survey Satellite (TESS) mission. The host star, TOI-700 (TIC 150428135), is a nearby (31.1 pc), inactive, M2.5 dwarf ($V_{mag} = 13.15$). TOI-700 is already known to host three planets, including the small, HZ planet, TOI-700 d. The new planet has an orbital period of 27.8 days and, based on its radius (0.95 R$_\oplus$), it is likely rocky. TOI-700 was observed for 21 sectors over Years 1 and 3 of the TESS mission, including 10 sectors at 20-second cadence in Year 3. Using this full set of TESS data and additional follow-up observations, we identify, validate, and characterize TOI-700 e. This discovery adds another world to the short list of small, HZ planets transiting nearby and bright host stars. Such systems, where the stars are bright enough that follow-up observations are possible to constrain planet masses and atmospheres using current and future facilities, are incredibly valuable. The presence of multiple small, HZ planets makes this system even more enticing for follow-up observations.