IMAGING PHOTOMETRY AND COLOR OF COMET SHOEMAKER-LEVY-9

An investigation of brightness and color of Comet SL9 was carried out, when the comet had a phase angle less than 1 degrees, The color of th e subnuclei was the same within error limits and was close to solar co lor, The g-r color of the dust increases along the tails of the subnuc lei until they merge in the common dust envelope, Similarly in the com mon dust envelope there seems to be a trend of increased reddening wit h increased distance from the chain of subnuclei. The brightness peaks at minimum phase angle, Comparison viith other observers indicates a phase curve similar to the phase dependence observed in C-type asteroi ds, The comet did not change its appearance when it passed minimum pha se angle, This means that there is no evidence for fresh dust leaving the subnuclei in the form of syndyne tails or ongoing fragmentation pr oducing micrometer-sized particles in the common dust envelope, We con clude that most of the dust present in the image was emitted either at breakup of the parent nucleus or a little later, As in this case the grains must be large as compared to the visual wavelength we can inter pret the color as color of a macroscopic body, The fact that it is clo se to the solar color is consistent with the color of C-type asteroids . The color trend, if real, could then be due to separation of brighte r and redder grains from the dark carbonaceous component by radiation pressure. (C) 1996 Academic Press, Inc.