Rocky planets might need to be the right age to support life

Extrasolar planets are being discovered at a rapid rate—4,531 planets in 3,363 systems (with another 7,798 candidates awaiting confirmation). Of these, 166 have been identified as rocky planets (also known as “Earth-like”), while another 1,389 have been categorized as rocky planets that are several times the size of Earth (“Super-Earths”). As more and more discoveries are made, the focus of astronomers is shifting from the discovery process towards characterization.