Finding aliens means studying new sorts of planet

On September12th , at a conference on life in the universe hosted by Harvard University, David Charbonneau, an astronomer at that same university, gave a talk titled “The terrestrial planets of the smallest and closest stars”. The unofficial title, as revealed on his second slide, was “Small angry stars and the many godforsaken rocks which orbit them”.Astronomers have now found more than 5,500 planets around other stars, or exoplanets, most of them detected by means of the small dip in the star’s light that happens when the planet passes across its face, and the planet’s shadow thus passes across the Earth. Hundreds of these sit in their parent star’s “habitable zone”, which means they orbit neither so close that any water on their surfaces would boil away, nor so far that it would be frozen. Since water is vital to every form of life known on Earth, such potential sogginess is much prized by scientists interested in whether some exoplanets might harbour life of their own.