The TESS (Transiting Exoplanet Survey Satellite) mission has discovered many exoplanet candidates that need to be confirmed and characterized from the ground. One of them orbits Ross 176, a K-type dwarf star, where we have identified a promising hot “water-world” candidate.
Using spectroscopic observations with the CARMENES instrument, we confirmed the planetary nature of the signal detected by TESS and estimated the planet’s mass. To improve the analysis, we applied an advanced statistical method called Gaussian Process, which allowed us to separate the star’s own variability (quite strong, with a rotation period of about 32 days) from the planetary signal.
The planet, named Ross 176 b, is a transiting world orbiting very close to its host star every 5 days. It has an equilibrium temperature of around 680 K, a radius of 1.84 times of Earth size, a mass of 4.6 times of Earth mass, and a density consistent with a water-rich composition.
Because of these characteristics, Ross 176 b is a promising target for future atmospheric studies, which could provide key insights into the existence and formation of water worlds. This discovery also adds to the growing sample of planets orbiting K-type stars, which is crucial for understanding the population of small-radius exoplanets around this type of star. Finally, it highlights the power of combining data from space-based missions like TESS with ground-based observations like those from CARMENES to confirm and characterize new planets.