Astronomers say they now know more about the TRAPPIST-1 system, 40 light-years away, than any other besides our own – and it looks like there’s a lot of water on its planets.
Four studies have been published, including in Nature Astronomy and Astronomy and Astrophysics, that give us a fascinating glimpse at these seven worlds. Perhaps most excitingly, astronomers report that up to 5 percent of some of the planets’ mass may be water – 250 times that on Earth.
“The form that water would take on TRAPPIST-1 planets would depend on the amount of heat they receive from their star, which is a mere 9 percent as massive as our Sun,” NASA noted in a statement.
The three outermost planets – f, g, and h – are thought to be far enough from the star that their water is frozen as ice. However, three of the planets (e, f, and g) orbit in the star’s habitable zone. TRAPPIST-1e in particular looks like it could host water, while the innermost planets may contain water in the form of atmospheric vapor, like Venus in our Solar System.
Scientists probed the planets using data from NASA’s Hubble, Kepler, and Spitzer space telescopes. They found that all seven planets were likely made of rock, and they all had the potential to be temperate, bearing a striking similarity to the rocky worlds in our Solar System.
One of the planets in particular, TRAPPIST-1e, which is the fourth from the star, appears to be the most Earth-like in the system in terms of its size and density. Of the seven planets, it is the only one to be slightly more dense than our own, suggesting its iron core – if it has one – is denser than ours.