About this world
LP 791-18 d is an Earth-sized planet orbiting LP 791-18, a cool red dwarf (type M(6.1+/) 86.4 light-years from Earth. It is about 1 times the size of Earth and holds 0.91 Earth masses. It completes an orbit every 2.75 days at 0.02 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 396 K (122 °C): too cold for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock. Its atmosphere has already been studied: 5 spectroscopic observations, all of them with the James Webb Space Telescope.
It was discovered in 2023 by transit with Spitzer Space Telescope. A planet crosses its star and dims it by a tiny, periodic fraction. LP 791-18 has 3 known planets; the others are LP 791-18 b and LP 791-18 c.