TRAPPIST-1
TRAPPIST-1 is an ultra-cool red dwarf with seven known planets. It is estimated to be 7.6 billion years old—older than the Solar System.
Briefing
TRAPPIST-1—also known as 2MASS J23062928−0502285 or SPECULOOS-1—is a red dwarf star in the constellation Aquarius, approximately 40.66 light-years from Earth. It has a surface temperature of about 2,566 K, a radius slightly larger than Jupiter’s, and a mass of about 9% of the Sun.
How we know
Observations in 2016 from TRAPPIST–South (the Transiting Planets and Planetesimals Small Telescope project) at La Silla Observatory in Chile, together with other telescopes, led to the discovery of two terrestrial planets orbiting TRAPPIST-1. In 2017, further analysis of the original observations identified five more terrestrial planets; seen from Earth, the planets pass in front of the star, an alignment that allows their presence to be inferred from the repeated pattern of their orbits, which range from 1.5 to 19 days and are described as circular.
- Unseen
- No apparent magnitude or practical observing guidance is provided in the supplied material; in this entry, TRAPPIST-1 remains a star known through telescopes and analysis rather than a described naked-eye or small-telescope target.
