Discovery of four mini-Neptunes around red dwarfs stuns astronomers

Using ground-based telescopes and a space observatory, scientists have discovered four mini-Neptunes around four red dwarfs. All of these planets are very close to their parent stars.

Astronomers from the National Astronomical Observatory of Japan are credited with the discovery. They explain that planets sized between Earth and Neptune are relatively common in the universe. These planets, absent in the Solar System, are called mini-Neptunes.

The Japanese team has presented four such planets (TOI-782 b, TOI-1448 b, TOI-2120 b, and TOI-2406 b) orbiting red dwarf stars. They were detected using a global network of ground-based telescopes and the TESS (Transiting Exoplanet Survey Satellite) space telescope.

The discovered mini-Neptunes have diameters 2 to 3 times larger than Earth, and they orbit their stars in less than 8 days. At least three of the four planets have eccentric orbits, which is surprising because, with such short periods, one would expect circular orbits.

According to scientists, the three planets mentioned have maintained unusual orbits for several billion years.

Measurements of star vibrations caused by planet movement, conducted by the Subaru telescope, indicated that the discovered mini-Neptunes have masses no greater than twenty times the mass of Earth.

The measured masses and diameters indicate that the planets do not have rocky compositions – their interiors are most likely filled with volatile substances. They largely resemble Neptune.

Scientists emphasize that planets of this type orbiting close to stars are interesting targets for studying exoplanet atmospheres using the James Webb Space Telescope. Further research is also expected to allow a better understanding of the interiors of such objects.