Submillimeter continuum observations of comet Hyakutake (1996 B2)

We report submillimeter continuum observations of comet Hyakutake (1996 B2) in the wavelength range 350 less than or equal to lambda less than or equal to 2000 mu m. 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 mu m is (1.16+/-0.12)x10(2) km(2), corresponding to a dust mass M approximate to 1.8X10(9) kg and a dust mass production rate dM/dt approximate to 2.8X10(4) kg s(-1). The gradient of the emission spectrum is relatively flat, with an opacity index beta=0.89+/-0.10. The cometary beta is comparable to values measured in the circumstellar disks of young stars. A small map at 800 mu m shows a coma radial surface brightness variation that is compatible with steady emission of solids from the nucleus on timescales approximate to 0.7 day. (C) 1997 American Astronomical Society.