Artist's View of Planets Transiting Red Dwarf Star in TRAPPIST-1 System
This illustration shows two Earth-sized worlds passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. The planets, TRAPPIST-1b and TRAPPIST-1c, reside 40 light-years away. They are between 20 and 100 times closer to their star than Earth is to the sun. Researchers think that at least one of the planets, and possibly both, may be within the star's habitable zone, where moderate temperatures could allow for liquid water on the surface. Hubble looked for evidence of extended atmospheres around both planets and didn't find anything. This leaves open the possibility the planets have thinner, denser atmospheres like Earth's.