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Astron. Astrophys. 337, 945-954 (1998)

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8. Conclusions

The unambiguous detection of the nucleus of comet 19P/Borrelly with the Hubble Space Telescope reveals a highly elongated body with semi-axes of [FORMULA] km and [FORMULA] km (yielding [FORMULA]), and rotating with a synodic period of [FORMULA] hr. Our interpretation of the observed lightcurve as resulting from the rotation of a prolate spheroid gives an orientation of the spin axis consistent with that derived by Sekanina (1979); however, the constraints on the orientation are not very strong. Although the size of 19P/Borrelly's nucleus is approximately half that of comet 1P/Halley, the rotational period of 25 hr and the fractional active area of 8% suggest some similarity between the two nuclei: both are more active and probably less evolved than the majority of the short-period comets. Comet 19P/Borrelly exhibits a complex coma dominated by a strong dust fan in the solar direction. We are presently investigating its detailed morphology to determine the pattern of active areas on the nucleus.

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© European Southern Observatory (ESO) 1998

Online publication: August 27, 1998