Results from the Hubble Space Telescope suggest there could be substantial amounts of water on some of the seven, Earth-sized planets orbiting the dwarf star TRAPPIST-1, which is 40 lightyears away, according to a Hubble Space Telescope press release.

Why it matters: Three of these planets fall within Trappist-1's 'habitable zone', which means the planets are the right distance from their star to theoretically support life. When they were discovered earlier this year, scientists suspected there would be water on these planets, but this is the first evidence that it hasn't been all been blown away by the star's radiation.

MIT's Julien de Wit, a co-author on the study: "This concludes that a few of these outer planets could have been able to hold onto some water, if they accumulated enough during their formation. But we need to gather more information and actually see a hint of water, which we haven't found yet."

How it happened: Scientists speculate that the planets were born in the icy outer reaches of their system, and captured water as they were born. When ultraviolet radiation from a star hits a planet's atmosphere, it can break up water there into its constituents oxygen and hydrogen, which can then escape the atmosphere and be detected as an indicator of water. The Hubble researchers used the telescope to measure UV radiation from the star and found that enough was emitted that the inner planets may have lost most of any water that was once there, but three outer planets could still hold water today.