Space Telescope Science
Only 40 light-years away — a stone’s throw on the scale of our galaxy — several Earth-sized planets orbit the red dwarf star TRAPPIST-1. Four of the planets lie in the star’s habitable zone, a region at a distance from the star where liquid water, the key to life as we know it, could exist on the planets’ surfaces.
Astronomers using NASA's Hubble Space Telescope have conducted the first spectroscopic survey of these worlds. Hubble reveals that at least three of the exoplanets do not seem to contain puffy, hydrogen-rich atmospheres similar to gaseous planets such as Neptune. This means the atmospheres may be more shallow and rich in heavier gases like those found in Earth’s atmosphere, such as carbon dioxide, methane, and oxygen.
Astronomers plan to use NASA’s James Webb Space Telescope, scheduled to launch in 2019, to probe deeper into the planetary atmospheres to search for the presence of such elements that could offer hints of whether these far-flung worlds are habitable.