Seven planets orbiting the ultracool dwarf star TRAPPIST-1

This is an artist’s impression of the TRAPPIST-1 system, showcasing all seven planets in various phases. When a planet transits across the disk of the red dwarf host star, as two of the planets here are shown to do, it creates a dip in the star’s light that can be detected from Earth.

Also during such transits astronomers are able to study the potential atmospheres of these planets.