TRAPPIST-1d is a confirmed exoplanet orbiting the ultra cool brown dwarf star TRAPPIST-1, 39 light years away from Earth. It is one of 7 planets that were discovered using the transit method in February 2017. It is one of 4 planets that are orbiting in the habitable zone of their parent star. The other planets are TRAPPIST-1b, c, e, f, g and h.
The parent star, TRAPPIST-1, has a mass of 0.08 Suns, a radius of 0.117 Suns (slightly larger than Jupiter, but slightly smaller than Kepler-7b), a temperature of 2559 K (2285.85 C), and is 500 million years old (which makes the star and its planets much younger than Earth, which is 4.55 billion years old). The TRAPPIST-1 system was formed during Earth's Cambrian Period.
(Mass: 0.41 Earths; Radius: 0.772 Earths; Earth Similarity Index: 0.897; Stellar flux: 1.1486)