Submillimeter Continuum Observations of Comet Hyakutake (1196 B2)

We report submillimeter continuum observations of comet Hyakutake (1996 B2) in the wavelength range 350≤λ≤2000 μm. Submillimeter continuum emanates primarily from large (millimeter sized), solid particles in the coma. C/Hyakutake was the strongest source of cometary submillimeter radiation observed to date, allowing new measurements of unprecedented quality. The equivalent blackbody cross section at 800 μm is (1.16±0.l2)×10²km², corresponding to a dust mass M≈1.8×10⁹ kg and a dust mass production rate M/dt≈=2.8×l0⁴ kg s^-1. The gradient of the emission spectrum is relatively flat, with an opacity index Β=.89±0.10. The cometary P is comparable to values measured in the circumstellar disks of young stars. A small map at 800 μm shows a coma radial surface brightness variation that is compatible with steady emission of solids from the nucleus on timescales ≈0.7 day.