Memorable Comets

Comet Tuttle-Giacobini-Kresak
41P/Tuttle-Giacobini-Kresak

    Comet Tuttle-Giacobini-Kresak is a periodic comet with the designation 41P. Most of these old periodic comets were discovered visually by comet hunters. This is a short period comet of a 5-year orbital period and first appeared in 1858 . After having escaped several attempts to recover, it was found in April 1951 in the constellation of Leo in the evening sky as a 10th-magnitude comet by Dr. Kresak during his comet search at Skalnate Pleso Observatory in Czechoslovakia　(present Slovakia). It was a discovery by 10cm binoculars and immediately reported as a new comet to the Central Bureau for Astronomical Telegrams in Copenhagen. It was many decades later that it was confirmed to be Comet Tuttle reappearing after 50 years. In fact, Tanakami Astronomical Circular-Letter issued in June 1951 reported that Comet Kresak was Comet Tuttle 2.
    Since then the comet has been recovered mostly with a regularity. However, at its apparition of May 1973 something unusual happened. It was predicted to become 15th magnitude, but in June it suddenly brightened to 4th magnitude. It became a substantial comet with a trailing tail and faintly visible to the naked eye. Dr. Kresak, the third discoverer of the comet, observed this phenomenon and said that this comet had lost most of its energy after two outbursts at this apparition, suggesting that he was pessimistic about its next apparition.
    The next apparition was predicted to be 5 years later in December 1978. Dr. Marsden of BAA predicted the magnitude of its nucleus to be fainter than 20, perhaps considering Dr. Kresak's view. What's more, the comet would appear under the worst observing conditions: it would be close to the sun and less than 20 degrees in altitude in the beginning morning twilight. Under these conditions, the recovery would be impossible and no observatories in the world would try to search for it. The "lost" Comet Tuttle-Giacobini-Kresak would quietly turn around the sun and head back toward distance space without being seen by anybody.

    At 5 am of November 9 ,1978, Geisei's 40cm reflector captured the comet right on the spot. Venus at the greatest west elongation was blazing less than one degree from the comet swamping its feeble light. But the comet was bright enough to be barely detectable at 17th magnitude.
    In spite of Dr. Kresak's concern, the comet made an impressive return shining at the normal total magnitude. There were no observations at this apparition other than Geisei's. Geisei continued to track the comet until January 1979. What is presented here is one of the photographic plates exposed during the observation of this comet. Numerous scratches are the reminiscence of the passing of time since the recovery, but the plate is now restored to an extent that it is presentable. The comet on the plate is hazy like fog without a nucleus.