Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt
Journal article, 2012
Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets(1). Collisions between such bodies produce small dust particles(2), the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2-2xFe2xSiO4) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids(5,6) (x approximate to 0.29). In the cold outskirts of the beta Pictoris system, an analogue to the young Solar System, olivine crystals were detected(7) but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets(8,9). Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of beta Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 +/- 0.001) and show that they make up 3.6 +/- 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System(8-10), even though beta Pictoris is more massive and more luminous and has a different planetary system architecture.
forsterite
protoplanetary disks
silicates
hd 100546
dust
chondrites
spectroscopy
debris disks
beta-pictoris
spectra
Author
B. L. de Vries
KU Leuven
B. Acke
KU Leuven
Jadl Blommaert
KU Leuven
C. Waelkens
KU Leuven
Lbfm Waters
Anton Pannekoek Institute for Astronomy
Netherlands Institute for Space Research (SRON)
B. Vandenbussche
KU Leuven
M. Min
Anton Pannekoek Institute for Astronomy
G. Olofsson
Stockholm University
C. Dominik
Anton Pannekoek Institute for Astronomy
Radboud University
L. Decin
Anton Pannekoek Institute for Astronomy
KU Leuven
M. J. Barlow
University College London (UCL)
A. Brandeker
Stockholm University
J. Di Francesco
National Research Council Canada
A. M. Glauser
Royal Observatory
Swiss Federal Institute of Technology in Zürich (ETH)
J. S. Greaves
SUPA
P. M. Harvey
The University of Texas at Austin
W. S. Holland
Royal Observatory
University of Edinburgh
R. J. Ivison
Royal Observatory
René Liseau
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
E. Pantin
Centre national de la recherche scientifique (CNRS)
G.L. Pilbratt
European Space Agency (ESA)
P. Royer
KU Leuven
B. Sibthorpe
Royal Observatory
Nature
0028-0836 (ISSN) 1476-4687 (eISSN)
Vol. 490 7418 74-76Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1038/nature11469