A dust ring around Epsilon Eridani: analogue to the young Solar System

Dust emission around the nearby star ǫ Eridani has been imaged using a new submillimetre camera (SCUBA at the JCMT). At 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 the ring structure is that it is a young analogue 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 ǫ 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. ǫ Eri is a main-sequence star of type K2V (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 substructure within the ring, and these asymmetries could be due to perturbations by planets. Subject headings: planetary systems – stars: individual: ǫ Eridani – circumstellar matter