About this world
TRAPPIST-1 g is an Earth-sized planet orbiting TRAPPIST-1, a cool red dwarf (type M8.0V) 40.5 light-years from Earth. It is about 1.1 times the size of Earth and holds 1.3 Earth masses. It completes an orbit every 12.4 days at 0.047 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 197 K (−76 °C), which places it in the conservative habitable zone: the band where liquid water could exist on a rocky surface. By the "cosmic shoreline", it has likely held on to an atmosphere. Its atmosphere has already been studied: 3 spectroscopic observations, all of them with the James Webb Space Telescope.
It was discovered in 2017 by transit with Multiple Observatories. A planet crosses its star and dims it by a tiny, periodic fraction. TRAPPIST-1 has 7 known planets; the others are TRAPPIST-1 b, TRAPPIST-1 c, TRAPPIST-1 d, TRAPPIST-1 e, TRAPPIST-1 f and TRAPPIST-1 h.