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

Almost 5 billion years ago, the Sun formed in a local contraction of a clou d 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, a nd to have formed the planets, comets and other Solar System objects. Simil ar disks, but with less mass, have been observed around a few main-sequence stars such as Vega(1), The dust particles orbiting stars like Vega will be removed on timescales of the order of 1 Myr (Vega is about 350 Myr old), a nd therefore must be resupplied(1), at least for a time. But earlier survey s(2,3) lacked the sensitivity to determine how many nearby stars have dust disks, and to investigate how long such disks survive. Here we report infra red observations indicating that most stars younger than 300 Myr have dust disks, while most older than 400 Myr do not: ninety per cent of the disks d isappear when the star is between 300 and 400 Myr old. Several events that are related to the 'clean up' of debris in the early history of our Solar S ystem have a similar timescale.