Mass, radius, and temperature TRAPPIST-1h has a radius of , a mass of , and about 57% Earth's surface gravity. since it only receives about 13% of the stellar flux that Earth does. It has an equilibrium temperature of , similar to that of Earth's south pole.
Host star TRAPPIST-1h orbits the ultracool dwarf star TRAPPIST-1. It is 0.121 and 0.089 Solar mass|, with a temperature of 2,511 K and an age between 3 and 8 billion years. For comparison, the Sun has a temperature of 5,778 K and is about 4.5 billion years old. TRAPPIST-1 is also very dim, with about 0.0005 times the
luminosity of the Sun. The star's
apparent magnitude, or how bright it appears from Earth's perspective, is 18.8. Therefore, it is too dim to be seen with the naked eye.
Orbit Despite it being the most distant known planet in its system, TRAPPIST-1h orbits its host star with an orbital period of 18.868 days and an orbital radius of about 0.0619
AU. This is even smaller than
Mercury's orbit around the Sun (which is about 0.38 AU). and 2022. If ice-covered, it could also potentially harbor a subsurface ocean by way of
tidal heating, which could lead to
cryovolcanism in the form of erupting
geysers. ==See also==