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P/2010 V1 (Ikeya-Murakami)


On Nov. 2 and 3, 2010, respectively, Japanese amateur astronomers Kaoru Ikeya (25cm-Reflector) and Shigeki Murakami (46cm-Reflector) independently discovered a comet in the constellation Virgo, not far from Saturn. The discoverers reported comet P/2010 V1 (Ikeya-Murakami) to be about magnitude 8.5. While Ikeya described the coma as 1' in diameter, diffuse and with moderate condensation, Murakami reported a 4' coma and a 2' tail in p.a. 90° (IAUC 9175/76 and MPEC 2010-V110). The absolute brightness derived from these observations is very high and implies that this comet should already have been found by the automated search programs around the turn of this year. This suggests that the comet is in a state of outburst, which is supported by the fact that K. Ikeya could not detect any sign of a suspicious object at the position of the comet the day before, despite better observing conditions (IAUC 9183). Thus it is probable that the brightness will decrease according to a dt-Formula during the winter months. The comet passed its perihelion on Oct. 25 and will move through the constellations of Virgo, Libra and Scorpius until March 2011, being a morning sky object which reaches its maximum altitude of only 20° for mid-European observers in December.

The comet could be seen for only a short time near the morning horizon. Thus it is not surprising that very few observations were published. The following very preliminary analysis is based on only 23 international observations and 1 from a member of the German Comet Section. These clearly indicate that the comet was discovered due to an outburst. Not surprisingly the maximum brightness of 7.8 mag was reached at the date of discovery. Thereafter the comet faded continuously, reaching 10.0 mag at the end of November. This evolution can be described quite well using the formula

m = 4.7 mag + 5×log D + 0.12×(t-T)

The assumption of an outburst is further supported by the evolution of the degree of condensation. It decreased rapidly from DC 6-7 at discovery to DC 2 at the end of November. The evolution of the coma diameter is not as obvious. It seems to have marginally increased during the short apparition from 4' (450.000 km) to 5' (525.000 km).

Total Brightness and Coma Diameter

Additional astrometric observations revealed that the comet rounds the sun with an orbital period of 5.4 years (IAUC 9189). However, it is quite probable that it has already dissolved.

Andreas Kammerer


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