Letter | Published:

An early extrasolar planetary system revealed by planetesimal belts in β Pictoris

Abstract

β Pictoris (β Pic) is a main-sequence star with an edge-on dust disk1,2,3 that might represent a state of the early Solar System. The dust does not seem to be a remnant from the original protoplanetary disk, but rather is thought to have been generated from large bodies like planetesimals and/or comets4,5. The history and composition of the parent bodies can therefore be revealed by determining the spatial distribution, grain size, composition and crystallinity of the dust through high-resolution mid-infrared observations. Here we report that the sub-micrometre amorphous silicate grains around β Pic have peaks in their distribution around 6, 16 and 30 au (1 au is the Sun–Earth distance), whereas the crystalline and micrometre-sized amorphous silicate grains are concentrated in the disk centre. As sub-micrometre grains are blown quickly out from the system by radiation pressure from the central star, the peaks indicate the locations of ongoing dust replenishment, which originates from ring-like distributions of planetesimals or ‘planetesimal belts’.

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Acknowledgements

This Letter is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We thank C. Koike, I. Yamamura, F. Usui, S. Hasegawa, T. Ootsubo, H. Chihara, T. Nakamoto, H. Tanaka and T. Takeuchi for comments and discussions.

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Correspondence to Yoshiko Kataza Okamoto.

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Figure 1: Spectra of β Pic after subtraction of the photospheric emission.
Figure 2: Distribution of each dust emission.
Figure 3: Conceptual view of the discovered planetesimal belts.

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