Low density super earth TOI-2211 b characterized as a potential hot water world

Researchers have performed a detailed characterization of the exoplanet TOI-2211 b, a super-Earth orbiting an orange dwarf star. By combining data from multiple telescopes, the study identified the planet as a promising candidate for a hot water world. Additionally, the team detected a second, non-transiting planetary candidate within the same system, providing new insights into the architecture of this distant star system.

Star system: TOI-2211 | Distance from the Sun: 230 light years

The exoplanet TOI-2211 b is a super-Earth located on a close orbit around an orange dwarf star, completing one revolution every 3.09 days. Because it is positioned so close to its host star, it is subjected to intense radiation that often strips away light primordial atmospheres made of hydrogen and helium. The current analysis indicates that the mass and radius of the planet are not consistent with a simple bare rocky interior, nor with an atmosphere dominated by hydrogen. Instead, it is likely that the planet possesses an atmosphere composed of heavier molecules, identifying it as a prime candidate for a hot water world.

To determine the physical properties of the system, data from the TESS and CHEOPS space telescopes were combined with radial velocity measurements taken by ground-based instruments including HARPS, ESPRESSO, and KPF. Radial velocity is a method that detects the subtle gravitational wobble of a star caused by the pull of its orbiting planets. This combined dataset allowed for a precise measurement of the planet, revealing a radius of 1.457 Earth radii and a mass of 2.69 Earth masses. In addition to the primary planet, the radial velocity data also revealed a second, outer planetary candidate that does not transit its host star, with an orbital period of approximately 15.6 days.

The findings provide a valuable target for future studies of planet formation and evolution. By analyzing the evaporation of volatile materials from the surface of TOI-2211 b, the results support the classification of the planet as a volatile-rich world, placing it within a growing group of low-density super-Earths that challenge standard models of how planetary systems develop.

Key findings
TOI-2211 b has a measured radius of 1.457 Earth radii and a mass of 2.69 Earth masses.
The planet is identified as a candidate for a hot water world due to its atmospheric characteristics.
A non-transiting planetary candidate was detected in the system with an orbital period of 15.6 days.
The system orbits an orange dwarf star with an orbital period of 3.09 days for the inner planet.

Scientific study

Searching for hot water world candidates with CHEOPS: II. A low-density super-Earth orbiting the K dwarf TOI-2211 (external link)