Letter
Nature 459, 227-229 (14 May 2009) | doi:10.1038/nature08032;
Received 11 January 2009; Accepted 31 March 2009
Radiation-pressure
mixing of large dust grains in protoplanetary disks
- Physics Department, University of Split, Nikole Tesle
12, 21000 Split, Croatia
Correspondence to: Dejan Vinkovi
1
Correspondence and requests for materials should be addressed to the author
(Email: vinkovic@pmfst.hr).
Abstract
Dusty disks around young stars are
formed out of interstellar dust that consists of amorphous, submicrometre
grains. Yet the grains found in comets1 and meteorites2, and traced in the spectra of young stars3, include large crystalline grains that
must have undergone annealing or condensation at temperatures in excess of
1,000 K, even though they are mixed with surrounding material that never
experienced temperatures as high as that4. This prompted theories of large-scale
mixing capable of transporting thermally altered grains from the inner, hot
part of accretion disks to outer, colder disk regions5, 6, 7, but all have assumptions that may be
problematic8, 9, 10, 11, 12. Here I report that infrared radiation
arising from the dusty disk can loft grains bigger than one micrometre out of
the inner disk, whereupon they are pushed outwards by stellar radiation
pressure while gliding above the disk. Grains re-enter the disk at radii where
it is too cold to produce sufficient infrared radiation-pressure support for a
given grain size and solid density. Properties of the observed disks suggest
that this process might be active in almost all young stellar objects and young
brown dwarfs.
