Outburst of COMET 17P/Holmes

Comet 17P/ Holmes had a massive outburst around 24.07 October, 2007.The comet brightened from a normalmagnitude of 17.8 to 3.5 on October 24.55 (IAUC 8886).

The comet was observed in the Z band at the HCT on 25 and 26 October. Figure 1 shows the images obtained on these two days. Top and lower left panels show the original processed images of 25 and 26 October respectively. North is top and East is to the left. The ejected debris is clearly seen in the south-westerly direction. The outburst plume
and the envelope are seen more clearly in the middle panels after the contribution of the 1/r coma is removed by division by a synthetic coma in which the intensity at a projected distance "r" from the comet center falls off as 1/r. Further details can be delineated by applying a digital filter using the "Shift-Rotation" algorithm. This filter
brings out details of the edges of the ejecta where the intensity gradient is maximum. The shell structure in these processed images should be interpreted as the edge of the expanding envelope
and is not a real feature.

The features on the two days appear alike except for expansion with a projected velocity of 0.4 - 0.45 km/s. The total image field is 3.55 X 10^5 km. The heliocentric and geocentric distances of the comet are 2.44 AU and 1.63 AU respectively.

(R. Vasundhara, K.Sasikumar Raja, P. Ramya, S. Muneer, Ravindra Pawase,Aman Preet kaur, Manjunath hegde)