Planets between the size of Earth and Uranus/Neptune, termed mini-Neptunes, do not exist in our Solar System but are common elsewhere. They are potential candidates for atmospheric analysis by the James Webb Space Telescope. What do mini-Neptunes look like?
The study found four transiting short-period mini-Neptunes (TOI-782 b, TOI-1448 b, TOI-2120 b, and TOI-2406 b) around red dwarfs using ground-based telescopes with MuSCATs. These mini-Neptunes have radii about 2-3 times that of Earth and orbital periods of less than eight days. Radial velocity measurements of their parent stars, obtained with the IRD on the Subaru telescope, show that the masses of these planets are less than 20 times that of Earth. The correlation between their measured radii and upper mass limits suggests these mini-Neptunes are not rocky planets like Earth but likely contain volatiles such as H2O and atmospheres.
The study also revealed that at least three (TOI-782 b, TOI-2120 b, TOI-2406 b) of these mini-Neptunes have eccentric orbits. In general, the orbit of a short-period planet around a red dwarf should be circular due to tidal dissipation. However, three short-period mini-Neptunes around red dwarfs have maintained non-zero eccentricities for billions of years. One possible interpretation of this is that their interiors are not susceptible to tidal effects. The mass-radius relationship suggests they are not rocky and might have interiors similar to Neptune. Short-period mini-Neptunes are promising targets for atmospheric observations with the James Webb Space Telescope. Further observations are expected to enhance understanding of their internal compositions and atmospheres.
Research Report:The Discovery and Follow-up of Four Transiting Short-Period Sub-Neptunes Orbiting M dwarfs
Related Links
Astronomical Observatory of Japan
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
