GJ 357 (Gliese 357) is a red dwarf star with an unusually low starspot activity. It is located 31 light-years from Earth, in the Hydra constellation.
Planetary system The star has three confirmed exoplanets in its orbit. One of these, GJ 357 d, is considered to be a super-Earth within the circumstellar habitable zone.Falconer, Rebecca, Newly uncovered super-Earth 31 light-years away may be habitable , Axios, August 1, 2019
Transmission spectroscopy of the planet b with JWST in 2025 found no clear evidence for atmospheric molecules, although a secondary atmosphere is considered likely to exist. Similarly, another 2025 analysis of the JWST transmission spectrum found no atmospheric molecules, but was able to rule out an atmosphere composed mainly of low-molar mass molecules (less than 8 g/mol) and an abundance of metals less than 300 times that of the Sun. A 2026 study found dayside temperature of () for the planet, which is considered anomalously high compared to previous predictions. The data is inconsistent with the predictions for an airless rock with an albedo of zero, and with several atmospheric compositions with high mean molar mass. Hot spots, untested atmospheric conditions, and wavelength-dependent surface emissivity could explain the anomalously high temperature.
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