TOI-122 b: A Neptune-Like World Around a Cool Red Dwarf

TOI-122 is an M3 V star, a small, cool red dwarf, located 203 light-years away. Its reported mass is 0.312 solar masses, its reported radius is 0.334 solar radii, and its reported temperature is 3400 K. This star's reported mass and radius estimates are smaller than the Sun's, and its reported temperature is cooler than the Sun's. Its age is given as a reported lower limit of 2 billion years, a bound rather than an exact value. One planet is known to orbit this host.

That planet, TOI-122 b, is a Neptune-like world discovered in 2020 by the transit method. Its orbital period is 5.08 days, and its radius is 2.72 Earth radii, larger than Earth's. Because a Neptune-like classification compares radius with Earth's, it places the planet in the size range reaching up to four times Earth's radius.