STRUCTURE IN THE ε ERIDANI DEBRIS DISK

摘要

New submillimeter images have been obtained of the dust disk around the nearby K2 V star ε Eridani, with the total data set now spanning 5 yr. These images show the distribution of dusty debris generated by comet collisions, reflecting clearing and perturbations by planets, and may give insights to early conditions in the solar system. The structure seen around ε Eri at 850 μm and published in 1998 is confirmed in the new observations, and the same structure is also seen in an image obtained for the first time at 450 μm. The disk is inclined by ≈25° to the sky plane, with emission peaking at 65 AU, a 105 AU radius outer edge, and an inner cavity fainter by a factor of ≈2. The structure within the dust ring suggests perturbations by a planet orbiting at tens of AU, and long-term tracking of these features will constrain its mass and location. A preliminary analysis shows that two clumps and one arc appear to follow the stellar motion (i.e., are not background objects) and have tentative evidence of counterclockwise rotation of ～1° yr~(-1). Within the ring, the mass of colliding comets is estimated at 5-9 M_⊕, similar to the primordial Kuiper Belt, and so any inner terrestrial planets may be undergoing an epoch of heavy bombardment.