The storm-lashed worlds of Trappist-1

The seven planets in orbit round a red dwarf star 39 light years away will provide valuable data about exoplanets and their atmospheres, but the latest data suggests that they are unlikely to be homely

Red dwarfs are thought to be the most common types of star, but all are dim. Even the red dwarf and the nearest star to the Sun, Proxima Centauri at 4.2 light years, is some 70 times too faint to be naked-eye-visible under the darkest sky. It was reported last summer that Proxima had a planet slightly larger than the Earth which orbited within its habitable zone where liquid water might survive on its surface given an adequate atmosphere.

The news of another red dwarf, Trappist-1, broke in February. It boasts seven Earth-class planets, of which three lie in or close to its habitable zone. At 39 light years, it is a thousand times dimmer than Proxima but, whereas Proxima is never visible from Britain, Trappist-1 lies in Aquarius below the Square of Pegasus, albeit swamped by our predawn twilight in the E and near Venus at present.