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.

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New submillimeter images have been obtained of the dust disk around the nearby K2 V star e 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 e Eri at 850 mm 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 mm. The disk is inclined by ≈25Њ 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 ∼1Њ yr Ϫ1 . 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.

In this paper we present the first observations of the Ophiuchus molecular cloud performed as part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey (GBS) with the SCUBA-2 instrument. We demonstrate methods for combining these data with previous HARP CO, Herschel, and IRAM N 2 H + observations in order to accurately quantify the properties of the SCUBA-2 sources in Ophiuchus. We produce a catalogue of all of the sources found by SCUBA-2. We separate these into protostars and starless cores. We list all of the starless cores and perform a full virial analysis, including external pressure. This is the first time that external pressure has been included in this level of detail. We find that the majority of our cores are either bound or virialised. Gravitational energy and external pressure are on average of a similar order of magnitude, but with some variation from region to region. We find that cores in the Oph A region are gravitationally bound prestellar cores, while cores in the Oph C and E regions are pressure-confined. We determine that N 2 H + is a good tracer of the bound material of prestellar cores, although we find some evidence for N 2 H + freezeout at the very highest core densities. We find that non-thermal linewidths decrease substantially between the gas traced by C 18 O and that traced by N 2 H + , indicating the dissipation of turbulence at higher densities. We find that the critical Bonnor-Ebert stability criterion is not a good indicator of the boundedness of our cores. We detect the pre-brown dwarf candidate Oph B-11 and find a flux density and mass consistent with previous work. We discuss regional variations in the nature of the cores and find further support for our previous hypothesis of a global evolutionary gradient across the cloud from southwest to northeast, indicating sequential star formation across the region.