The outburst of comet 17P/Holmes

Abstract

Comet 17P/Holmes had a massive outburst at approximately 2007 October 23.8 and its total brightness reached maximum (from m = 17 to m = 2.5) around 2007 October 25, about 1.7 days (42 hr) after the event. Following the first report of this extraordinary cometary outburst, comprehensive observations were obtained at the Lulin Observatory until early 2008 January by using broadband filters and narrowband cometary filters. The separation velocity, as projected on the plane of the sky, between the nucleus and the coma blob produced by the outburst has been estimated to be 0.132 ± 0.004 km s-1 from October 25.8 to November 1.6. The expansion speed, also projected on the plane of the sky of the dust shell has been found to be constant at a rate of approximately 0.554 ± 0.005 km s-1 from October 25.8 to November 1.6. The color on December 10 is slightly redder than that of the Sun. Our narrowband observations provide information on the production rates of gas species on October 31: log Q (CN) = 27.103 and log Q (C2) = 27.349. The resulting abundance ratios show that the comet 17P can be classified as a "typical comet" in terms of composition. © 2009. The American Astronomical Society. All rights reserved.