Earth-Sized Planets Forty Light Years Away Could Be Habitable

Finding seven earth-sized planets orbiting the nearby dwarf star TRAPPIST-1 was one thing, now astronomers suggest that three of the planets might still harbour substantial amounts of water, adding further weight to the idea that this trio of exoplanets could indeed be habitable. Scientists believe that for life as we know it to exist outside our own planet, surface water must be present. Recently, an worldwide team of scientists used the Hubble Space Telescope to assess the chances of water existing on these planets-and the results are promising.

The researchers measured the ultraviolet (UV) irradiation that the planets receive from TRAPPIST-1, as these UV rays cause water molecules to break apart into their constituent hydrogen and oxygen atoms - making them vulnerable to being driven off into space by the X-ray radiation from the star. With three planets in the habitable zone, then distant star system shows promising to host life some day.

"Ultraviolet radiation is an important factor in the atmospheric evolution of planets", Vincent Bourrier, one of the scientists who made this discovery, said in a statement.

This artist's concept allows us to imagine what it would be like to stand on the surface of TRAPPIST-1f.

Lower-energy UV radiation takes water molecules and splits them into hydrogen and oxygen via a process called photodissociation.

In February 2017, further study showed that there were seven planets, all rocky and of approximately Earth size, and hopes of extraterrestrial life grew.

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Because hydrogen gas is so light, it can escape the atmosphere of the exoplanets and be detected by Hubble, suggesting the possible presence of atmospheric water vapour. But it's also possible that the outermost four planets (e, f, g and h - the first three of which are in the star's habitable zone) lost less than three Earth-oceans' worth of water. This makes them much easier to observe.

"Our results indicate that atmospheric escape may play an important role in the evolution of these planets", said co-author Julien de Wit, of MIT.

These two planets, which receive the highest amount of ultraviolet energy, could have bled 20 Earth-oceans worth of water into space over the past eight billion years.

The observed amount of UV radiation emitted by the TRAPPIST-1 star indeed suggests that the planets could have lost enormous amounts of water over the course of their history.

"While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope (JWST), they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability", concludes Bourrier.

  • Toni Ryan