P. Lamy, Laboratoire d'Astronomie Spatiale, and his team report the detection of the nucleus of comet 55P with the Hubble Space Telescope (+ WFPC2) on Jan. 9 at Delta = 0.46 AU: "After removing the faint contribution of the coma to the central pixels, the magnitude of the nucleus was R = 16.62, showing no variation over 10 hr. For a geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg, the mean effective radius is 1.8 km, the largest uncertainty coming from the phase law. The red color of the nucleus is characterized by a normalized reflectivity gradient of 0.16 percent/nm." Visual m_1 estimates: Mar. 1.75 UT, 8.7 (V. Znojil, Brno, Czech R., 25x100 binoculars); 18.24, 9.7: (N. Biver, Honolulu, HI, 0.26-m reflector).
International Astronomical Union Circular
- Pub Date:
- March 1998