TRAPPIST-1 is an ultra-cool red dwarf star that is slightly larger, but much more massive, than the planet Jupiter, located about 40 light-years from the Sun in the constellation Aquarius.

1. Cayman T. Unterborn, Steven J. Desch, Natalie R. Hinkel & Alejandro Lorenzo. Inward migration of the TRAPPIST-1 planets as inferred from their water-rich compositions.Nature Astronomy, 2018 DOI: 10.1038/s41550-018-0411-6