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Comet Hyakutake ((:çʲakɯ̥take), formally designated C/1996 B2) is a comet, discovered on 31 January 1996,〔 that passed very close to Earth in March of that year. It was dubbed The Great Comet of 1996; its passage near the Earth was one of the closest cometary approaches of the previous 200 years. Hyakutake appeared very bright in the night sky and was widely seen around the world. The comet temporarily upstaged the much anticipated Comet Hale–Bopp, which was approaching the inner Solar System at the time. Scientific observations of the comet led to several discoveries. Most surprising to cometary scientists was the first discovery of X-ray emission from a comet, believed to have been caused by ionised solar wind particles interacting with neutral atoms in the coma of the comet. The Ulysses spacecraft unexpectedly crossed the comet's tail at a distance of more than or ) from the nucleus, showing that Hyakutake had the longest tail known for a comet. Hyakutake is a long-period comet. Before its most recent passage through the Solar System, its orbital period was about 17,000 years,〔〔 but the gravitational perturbation of the giant planets has increased this period to 70,000 years.〔〔 == Discovery == The comet was discovered on 31 January 1996,〔 by Yuji Hyakutake, an amateur astronomer from southern Japan.〔(【引用サイトリンク】NASA"> accessdate=9 January 2007 )〕 He had been searching for comets for years and had moved to Kagoshima Prefecture partly for the dark skies in nearby rural areas. He was using a powerful set of binoculars with objective lenses to scan the skies on the night of the discovery.〔For a photo of Hyakutake and his binocular, see (How Yuji Hyakutake Found His Comet ) (Sky&Telescope. Retrieved on 21 April 2008).〕 This comet was actually the second Comet Hyakutake; Hyakutake had discovered comet C/1995 Y1 several weeks earlier. While re-observing his first comet (which never became visible to the naked eye) and the surrounding patch of sky, Hyakutake was surprised to find another comet in almost the same position as the first had been. Hardly believing a second discovery so soon after the first, Hyakutake reported his observation to the National Astronomical Observatory of Japan the following morning. Later that day, the discovery was confirmed by independent observations. At the time of its discovery, the comet was shining at magnitude 11.0 and had a coma approximately 2.5 arcminutes across. It was approximately 2 astronomical units (AU) from the Sun. Later, a pre-discovery image of the comet was found on a photograph taken on January 1, when the comet was about 2.4 AU from the Sun and had a magnitude of 13.3. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Comet Hyakutake」の詳細全文を読む スポンサード リンク
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