Hyakutake Jets and Shells from Wendelstein
This unique series of eight near-nucleus images (1a - 4b) has been reproduced from CCD frames, obtained with the 80-cm telescope of the Mt. Wendelstein observatory (University of Munich) in Southern Bavaria during the night of March 23 - 24, 1996. The CCD camera MONICA was used for the observations. Observers were Otto Baernbandner and Hermann Boehnhardt. The data processing was done by Hauke Fiedler and Hermann Boehnhardt.
The image orientation is: North is down, East to the left. Pixel size is 0.5 arcsec, field of view is 175 x 275 arcsec.
The frames were flat-fielded and cleaned in the usual way. In order to enhance the structures of interest, two 'Laplace-filters' were used. The Laplace filter with width 15 (L-15) shows best the detailed structures close to the central brightness peak, while that with width 47 (L-47) is very advantageous for broad and faint structures.
The Munich astronomers found a lot of details by this quick-look processing. For instance, in the 2a filtered image, a prominent jet and a fainter one can be seen, in that of 1a two jets are visible. The most interesting features are the shells which appear mostly in the sunward coma hemisphere and which may be seen to evolve in the coma (see 2b and 3b). These features represent old jets from the previous revolution of the nucleus. For instance: in 3b, two shells are visible. The outer one is the remnant from the inner shell seen in 2b.
The plasma tail is also very well depicted in the frames. Some condensations are also visible (cf. the recent observations at Pic du Midi).
Here are the images (all 10 sec exposures through a V-filter):
March 23 (23:01 UT) 1a: L-15 [GIF,40k] and 1b: L-47 [GIF,25k] .
March 24 (01:33 UT) 2a: L-15 [GIF,40k] and 2b: L-47 [GIF,25k] .
March 24 (03:05 UT) 3a: L-15 [GIF,40k] and 3b: L-47 [GIF,25k] .
March 24 (04:09 UT) 4a: L-15 [GIF,40k] and 4b: L-47 [GIF,25k] .
The photos may be reproduced, if credit is given to the European Southern Observatory and the University of Munich Institute for Astronomy and Astrophysics (Observatory at Wendelstein).