TRAPPIST-1 is a small ultracool dwarf star with a luminosity roughly 1/1000th that of the Sun. Comparing the two at Wednesday’s news conference, lead author of the Nature paper, Michaël Gillon, said that if the Sun were scaled to the size of a basketball, TRAPPIST-1 would be a puny golf ball. The resulting paltry amount of heat means that three of the seven TRAPPIST-1 planets actually receive similar amounts of radiation as Venus, Earth and Mars.
It’s our Solar System in miniature, but could TRAPPIST-1 host another Earth? – Huffington Post