New exoplanets — especially potentially habitable ones — are always exciting news. The TRAPPIST-1 system is the latest such discovery, stealing all the hype from the previously hip Kepler-186. Habitable, however, is very different to inhabited so, what are the chances a civilisation exists (or did exist) in TRAPPIST-1?
As far as the inner planets are concerned, highly unlikely, unless they like being blasted with X-rays... a lot of X-rays. A team, lead by Vincent Bourrier of Switzerland's University of Geneva Observatory, analysed the radiation being emitted by TRAPPIST-1's sun — a class M dwarf. Their findings, which show low levels of Lyman-alpha radiation, relative to X-rays, suggests the star is quite young.
So far, so good. That is if you're not living on planets b or c. As Camille M. Carlisle of Sky and Telescope explains:
Although the ultraviolet level is low, the radiation overall is still high enough that it could strip an Earth-like atmosphere from the inner two planets, b and c, in 1 to 3 billion years; for the planets d, e, f, and g (e, f, and g are in the putative habitable zone), the process would take anywhere from 5 to 22 billion years. The team does see a hint of atmospheric escape from b and c, although the slight drop in starlight that implies it might instead be due to coronal variability.
I suppose the news isn't entirely unexpected. Mercury barely has an atmosphere and while Venus does, it's deadly to human life in 70 different ways.