Planet formation: Grainy pictures of new worlds

Abstract

We know that planetary bodies in our Solar System began by agglomeration of dust grains, rocks and mountain-sized asteroids. We also know that most of the work was done during the first 10 million years (Myr) after the Sun's birth, when the young star was encircled by an immense disk of grains and gas. But to go beyond this is not easy. Some 4.5 billion years after the main event, examination of our neighbouring worlds may never allow us to reconstruct fully how the Sun's early disk evolved into gaseous behemoths such as Jupiter and small rocky planets such as Earth. We must look elsewhere for better clues to our origins, and we find them in new studies of disks around three stars by Holland et al., and of a disk surrounding the star HR4796A by Jura et al., Jayawardhana et al. and Koerner et al.

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