A Dust Ring around ε Eridani: Analog to the Young Solar System

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Abstract
Dust emission around the nearby star Eridani has been imaged using a new submillimeter camera (the Submillimetre Common-User Bolometer Array at the James Clerk Maxwell Telescope). At an 850 μm wavelength, a ring of dust is seen peaking at 60 AU from the star and with much lower emission inside 30 AU. The mass of the ring is at least ~0.01 M⊕ in dust, while an upper limit of 0.4 M⊕ in molecular gas is imposed by CO observations. The total mass is comparable to the estimated amount of material, 0.04-0.3 M⊕, in comets orbiting the solar system. The most probable origin of the ring structure is that it is a young analog to the Kuiper Belt in our solar system and that the central region has been partially cleared by the formation of grains into planetesimals. Dust clearing around Eri is seen within the radius of Neptune's orbit, and the peak emission at 35-75 AU lies within the estimated Kuiper Belt zone of 30-100 AU radius. Eri is a main-sequence star of type K2 V (0.8 M⊙) with an estimated age of 0.5-1.0 Gyr, so this interpretation is consistent with the early history of the solar system where heavy bombardment occurred up to ≈ 0.6 Gyr. An unexpected discovery is the substructure within the ring, and these asymmetries could be due to perturbations by planets.
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