TRAPPIST-1 system could support life

Some of the recently discovered planets in the TRAPPIST solar system could potentially be habitable, according to scientists from the University of Warwick.

Using the Hubble telescope, scientists measured ultraviolet (UV) radiation from the dwarf star, TRAPPIST-1 emits onto planets in the solar system. These UV rays cause water molecules to split – a process known as photodissociation – into hydrogen and oxygen atoms. Coupled with higher energy radiation and X-rays that heat the planets’ upper atmosphere, hydrogen and oxygen escape the planets.

Habitable zone

This suggests the planets have lost large amounts of water over the course of their history. However, the outer planets of the system should have lost much less water, suggesting that they could have retained some on their surfaces.

Professor Peter Wheatley, from the University’s Astronomy and Astrophysics Group, said: “It is exciting that we can now study the environments of individual Earth-sized planets. Our results suggest that water, and potentially life, could have survived in the TRAPPIST-1 system, despite the relatively intense ultraviolet and X-ray irradiation of the planets."

TRAPPIST-1 is the planetary system with the largest number of Earth-sized planets discovered to date. The amount of observed UV radiation emitted by TRAPPIST-1 suggests some planets could have lost gigantic amounts of water over the course of their history.

This holds true for the innermost two planets, TRAPPIST-1b and c which may have lost more than twenty Earth oceans worth of water during the last eight billion years. However, the outer planets including e, f and g, which reside in the habitable zone, should still have retained water on their surfaces.

Vincent Bourrier, research leader from the Observatoire de l’Université de Genève in Switzerland, said: “While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, 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.”