Disappearance of stellar debris disks around main-sequence stars after 400 million years

Abstract

Almost 5 billion years ago, the Sun formed in a local contraction of a cloud of molecular gas. A rotating disk of gas and dust is believed to have fed material onto the proto-Sun for the first few million years of its life, and to have formed the planets, comets and other Solar System objects. Similar disks, but with less mass, have been observed around a few main-sequence stars such as Vega. The dust particles orbiting stars like Vega will be removed on timescales of the order of 1Myr (Vega is about 350Myr old), and therefore must be resupplied, at least for a time. But earlier surveys lacked the sensitivity to determine how many nearby stars have dust disks, and to investigate how long such disks survive. Here we report infrared observations indicating that most stars younger than 300Myr have dust disks, while most older than 400Myr do not: ninety per cent of the disks disappear when the star is between 300 and 400Myr old. Several events that are related to the `clean up' of debris in the early history of our Solar System have a similar timescale.