Cold sub-Neptune TOI-6981 b discovered orbiting near the water ice line

A new sub-Neptune planet, TOI-6981 b (LSPM J0804+1116 b), has been identified orbiting a Red dwarf star. The planet is notable for its cold temperature of approximately 170 Kelvin (minus 103 degrees Celsius), which positions it at the water ice line. This is the boundary in a star system where it is cold enough for water vapor to condense into solid ice. Its unique location and characteristics offer a rare opportunity to study cold planetary atmospheres outside of our solar system.

The planet orbits its host star once every 60.8 days and has a radius roughly 2.4 times that of Earth. Its host star is a small, relatively cool Red dwarf with a radius about 30 percent of our Sun's and a surface temperature of 3215 Kelvin. 

Researchers confirmed the presence of TOI-6981 b by combining ground-based telescope measurements of the star's brightness dips when the planet passes in front of it, alongside statistical verification and high-resolution spectroscopy, which analyzes the light coming from the system to determine chemical properties.

Due to its specific orbital distance and the planet's atmospheric suitability, it is a prime candidate for future observation by the James Webb Space Telescope. Studying TOI-6981 b may help test theories regarding cold chemistry, the potential existence of water-rich worlds known as Hycean planets, and how planets migrate within their home systems.

Key findings
- TOI-6981 b is a cold sub-Neptune with an equilibrium temperature of approximately 170 Kelvin.
- The planet orbits a Red dwarf host star every 60.8 days.
- It is located near the water ice line, where temperatures allow for the formation of water ice.
- The planet has a radius of 2.4 Earth radii.
- High suitability for follow-up atmospheric analysis using the James Webb Space Telescope.

Scientific study

TOI-6981 b: a transiting sub-Neptune at the water ice line (external link)