海尔-波普彗星自转周期的测定

MEASUREMENT OF THE ROTATION PERIOD OF COMET HALE BOPP

采用小波方法对海尔波普彗星的近核ＣＣＤ图像进行处理，并进一步分析了彗核的亮度中心周围的特征结构，从而提出了一种直观而有效的方法来测定海尔波普彗星投射在观测平面上的平均自转周期，结果为２４．４１±０．

By analyzing the near nucleus structure of Comet Hale Bopp in CCD images, which were taken with a 1.56m telescope and processed with the wavelet method, a direct and effective access has been provided for measuring the averge rotation period of the comet. Firstly, according to the apparent features of the comet, it was certain that the rotation period of its nucleus is neither very long nor very short. Then two jet points were identified and their positions in a processed CCD image selected from every observation night were measured independently. Since the variation of each jet point's position angle implies the rotation of comet nucleus, the difference of values in two successive days divided by time interval yields an average rotation period of the comet nucleus. In this way, three possible periods have been found. The correlation between the observational plane and the equatorial plane of comet nucleus was taken into consideration. Secondly, all the CCD images in 3 long duration observation nights have been processed. Then the most probable average period was found from the three possible ones. It has been finally decided to be about 24.41±0.96 hours and this was projected on the observational plane. Furthermore, the radial distances between neighboring shells were measured and the radial velocity of shells has been found to be about 172m/s.