January 2008

January 3
Comet Holmes is still visible to the naked eye.

    Comet Holmes experienced unprecedented outbursts in October last year. In the new year it is still visible to the naked eye in the northern sky. When I observed it by the naked eye at 21:00 on January 3, the comet had become definitely fainter than the Double Cluster in Perseus at 3.9 magnitude, but only slightly fainter than M31, the Andromeda Galaxy. Naturally, a comet becomes fainter as its distance from the sun increases. But the total magnitude of Comet Holmes has not decreased much since mid December. My observation of this phenomenon is that the brightness of this comet has not diminished much because the light-reflecting surface area has expanded as the size of the coma increases, though the surface brightness has fallen. In the 60cm reflector the nucleus has become increasingly dim and it is now fainter than 13th magnitude. This stellar nucleus is embedded in a smaller coma and the comet takes on an extremely strange appearance that a small comet resides in a large coma. The diameter of the "outer coma" captured by the 21cm f/3 Epsilon telescope reaches astonishing 71 arc minutes.
    　On the comet's next return the large outer coma will have disappeared and the small comet inside the large coma will return. I am looking forward to finding out what the comet will look like and how bright it will be on its next return.
    The image below is a black-and-white photograph taken by the low f-ratio 21cm Epsilon telescope. A strange faint coma is visible together with a very faint nucleus at the center.