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Reports from Geisei Observatory <October 15, 2013>

The changing nucleus of Comet Encke (2P/Encke)

    This is a photograph of Comet Encke again. Drastic changes have occurred to the appearance of this comet. In the previous photograph (October 2), a 17th-magnitude sharp stellar nucleus appeared to be immediately outside the coma, then it has collapsed and become a bright coma. I have measured its position and confirmed that the center of the coma is at the position of the previous star-like nucleus. The coma will grow and brighten until it passes perihelion. However, after passing perihelion and its heliocentric distance becoming larger, a sharp nucleus will form in the coma again. And near aphelion, only the nucleus will shine making the comet look like a star.
    I hope you start to observe this comet in mid-October, as, by then, it will have become bright enough to be visually observable. The predicted positions are published in the Comet Handbook for 2014 as seen in our Home Page. This comet was successfully observed near aphelion by Dr. Elizabeth Roemer in the 1960s as well as by Mr. Hidetaka Sato in recent years.

393-second-exposure at 3:22, October 14 (J.S.T.)
70cm f/7 reflector with Nikon D700 at ISO 1250
Copyright (C) 2013 Geisei Observatory

Copyright (C) 2013 Tsutomu Seki.