TOI-3984 A b: A Jupiter-like Planet Around a Cool Red Dwarf

TOI-3984 A is an M-type star, a small, cool red dwarf, located 355 light-years away. Its spectral type is given as M4+/-0.5. The star has an age of 2.9 billion years, a mass of 0.49 solar masses, a radius of 0.47 solar radii, and a temperature of 3480 K. Its reported mass and radius estimates are smaller than the Sun's, and its reported temperature is cooler than the Sun's. One planet is known to orbit this host.

That planet, TOI-3984 A b, is a Jupiter-like world discovered in 2023 by the transit method, in which a planet passes in front of its star from our viewpoint and causes a small dip in observed brightness. It orbits every 4.35 days. Its radius is 7.9 Earth radii, which exceeds 4 times Earth's radius, and its mass is 44 Earth masses, both larger than Earth's. Its mean density is 0.492 g/cm³, 0.0892 times Earth's.