TOI-5720 and Its Earth-Sized Planet

TOI-5720 is an M-type star located 117 light-years away. Its spectral type is M3.5 +/- 1.0, placing it among the small, cool red dwarfs. The star has a reported mass of 0.383 solar masses and a radius of 0.383 solar radii, both smaller than the Sun's corresponding values. Its temperature is 3330 K, cooler than the Sun's. A reported lower limit on its age is 5 billion years. One known planet orbits this host.

That planet is TOI-5720 b, discovered in 2024 by the transit method, in which a planet passing in front of its star slightly dims the observed brightness. Repeating dips help establish the planet's orbital period. TOI-5720 b completes one orbit in 1.43 days. Its radius is 1.09 Earth radii, larger than Earth's, which places it within the Earth-like size class, since an Earth-like planet stays within 1.5 times Earth's radius. Its mass is a reported upper limit of 4.3 Earth masses.