Determination of the ejection velocities of Comet Hale-Bopp's jets

The wavelet analysis method is brought into use to process the charge coupl ed device (CCD) images of Comet Hale-Bopp, which were obtained with the 1.5 6 m telescope of Shanghai Astronomical Observatory. This method can elimina te the coma and show the features of jets. It is possible to measure the ej ection velocities (EV) of the jets by comparing the distances between the c ometary nucleus and the brightness center of the jets on different days. Ac cording to the reported rotation period of Comet Hale-Bopp, which is about 12 h, the average EV of the jets is determined to be (599 +/- 34) m/s based on 27 measurements. In addition, it is discovered that the velocity is dif ferent for each jet and for each different day, with a variation ranging fr om 200 to 900 m/s.