An international group of astronomers announced the discovery of sub-Neptune TOI-2257b: it is twice as large as Earth and may contain water.
The researchers observed the M-dwarf TOI-2257 and noticed that the star had a transit signal on the light curve – this phenomenon suggests that the star’s light is covering another object.
The planetary nature of this signal has been confirmed by subsequent observations using ground-based means.
After these observations, astronomers discovered TOI-2257b – this is a sub-Neptune, which they began to study with the TESS telescope, based on the results of observations, the information that the planet is located at these coordinates was confirmed.
The discovered sub-Neptune has a radius of about 2.19 Earths, it is 5.71 times heavier than our planet and makes a complete revolution around the parent star in 35.19 days. Astronomers have estimated the equilibrium temperature at 256 K.
The authors noted that sub-Neptune has a relatively long orbital period – to date, only two other exoplanets with periods longer than TOI-2257b are known. Therefore, they concluded that it could even contain liquid water.