TOI-663: A Cool Dwarf with Three Super-Earths

TOI-663 is an M1 V star located 209 light-years away. The "M1 V" spectral type marks it as a small, cool red dwarf. Its reported mass is 0.514 solar masses, its reported radius is 0.512 solar radii, and its reported temperature is 3680 K. Three planets orbit this star, all discovered in 2024 by the transit method and all classified as Super-Earths.

TOI-663 b has a mass of 4.45 Earth masses, a radius of 2.27 Earth radii, and an orbital period of 2.6 days. Its mean density is 2.1 g/cm³, 0.38 times Earth's. TOI-663 c has a mass of 3.65 Earth masses, a radius of 2.26 Earth radii, and an orbital period of 4.7 days. Its mean density is 1.74 g/cm³, 0.316 times Earth's. TOI-663 d has a reported upper limit of 5.2 Earth masses, a radius of 1.92 Earth radii, and an orbital period of 7.1 days.

Among the listed planets, TOI-663 b has the shortest year, TOI-663 c has the second-shortest year, and TOI-663 d has the longest year. TOI-663 b has the largest radius, TOI-663 c has the second-smallest radius, and TOI-663 d has the smallest radius. The radii of b and c are larger than Earth's, as is the radius of d. The masses of b and c are larger than Earth's, while the mass of d is an upper limit rather than an exact value.