September 1, 2017 - 17:30 AMT
Water may have been found on five Earth-sized planets

Scientists say it's possible five Earth-sized planets orbiting Trappist-1, an ultra-cool dwarf star located 39 light years away, contain "significant amounts of water," Engadget reports.

An international team of astronomers used the Hubble Space Telescope (HST) to measure the amount of ultraviolet (UV) radiation hitting all seven Trappist-1 exoplanets.

The phenomenon is important because low-energy UV radiation can break down water molecules into hydrogen and oxygen; higher levels heat the upper atmosphere to the point where the two elements can escape. UV radiation is therefore useful in modelling water loss and atmospheric stability in distant planets.

Measurements were taken with the HST's Space Telescope Imaging Spectograph in September, November and December last year. Using these figures and other scientific research, the team concluded that six of the exoplanets nearest Trappist-1 "could have lost more than 20 Earth oceans" of water throughout their history. While that sounds pretty bad, other possibilities exist. The team says the four planets furthest from the star, E, F, G and H, "might have lost less than three Earth oceans." B and C, the two closet to Trappist-1, are the least likely to hold water, unsurprisingly.

Planets E, F and G sit in the "habitable zone," an orbital distance that could, in theory, allow Earth-like planets to hold liquid water on their surface and, by extension, support life. It's here, of course, that scientists are most hopeful about the Trappist-1 system. Furthermore, depending on photolysis, which is the separation of molecules by light, it's possible all of the planets apart from B and C harbor water above ground. "Naturally, this also depends on the age of the system," the team of astronomers explain in their report, and how much water the planets originally formed with.