Three planets of ‘Holy Grail’ star system are ‘best place to search for aliens’

A star system which has been described as the ‘Holy Grail’ in the search for extraterrestrial life seems even more likely to host alien organisms after analysis by the Hubble Space Telescope.

Scans found three planets could be habitable, out of the seven Earth-sized planets orbit the ultracool dwarf star TRAPPIST-1, 40 light-years away from the Earth.

Scientists used the Hubble Space Telescope to scan four of the planets, finding that three are probably rocky and Earth-like, meaning it’s more likely they could support life.

Three of the planets orbit within the system’s habitable zone, the region at a distance from the star where liquid water, the key to life as we know it, could exist on the surface of a planet.

They’re not gas giants. Which means they might be more like us.

The fourth planet orbits in a borderline region at the inner edge of the habitable zone.

The data obtained rule out a cloud-free hydrogen-rich atmosphere for three of the planets.

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Dr Amaury Triaud, from the University of Birmingham, a leading member of the international team, said: ‘Of the seven planets, and of all the exoplanets that have been identified so far, Trappist-1e is the most resembling Earth, when we consider the amount of energy a planet receives from its star, and its density, which reflects its internal composition.

‘As our next step we would like to find out whether the planet has an atmosphere, since our only method to detect presence of biology beyond the solar system relies on studying the chemistry of an exoplanet’s atmosphere.’

Lead author Julien de Wit, from the Massachusetts Institute of Technology, USA, describes the positive implications of these measurements: ‘The presence of puffy, hydrogen-dominated atmospheres would have indicated that these planets are more likely gaseous worlds like Neptune.

‘The lack of hydrogen in their atmospheres further supports theories about the planets being terrestrial in nature.

‘This discovery is an important step towards determining if the planets might harbour liquid water on their surfaces, which could enable them to support living organisms.’