page_title: Comet Hyakutake
section_title: Orbit
hierarchical_section_title: Comet Hyakutake / Orbit
caption_attribution_description: English: en:Comet Hyakutake trajectory through the inner solar system, with a high inclination, its shown with vertical lines projecting the comet's positions onto the ecliptic.
context_page_description: Comet Hyakutake 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 500 million kilometres 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.
context_section_description: When the first calculations of the comet's orbit were made, scientists realized that it was going to pass just 0.1 AU from Earth on 25 March. Only four comets in the previous century had passed closer.  Comet Hale–Bopp was already being discussed as a possible "great comet"; the astronomical community eventually realised that Hyakutake might also become spectacular because of its close approach.
  Moreover, Comet Hyakutake's orbit meant that it had last been to the inner Solar System approximately 17,000 years earlier. Because it had probably passed close to the Sun several times before, the approach in 1996 would not be a maiden arrival from the Oort cloud, a place where comets with orbital periods of millions of years come from. Comets entering the inner Solar System for the first time may brighten rapidly before fading as they near the Sun, because a layer of highly volatile material evaporates. This was the case with Comet Kohoutek in 1973; it was initially touted as potentially spectacular, but only appeared moderately bright. Older comets show a more consistent brightening pattern. Thus, all indications suggested Comet Hyakutake would be bright.
  Besides approaching close to Earth, the comet would also be visible throughout the night to northern hemisphere observers at its closest approach because of its path, passing very close to the pole star. This would be an unusual occurrence, because most comets are close to the Sun in the sky when the comets are at their brightest, leading to the comets appearing in a sky not completely dark.
caption: Comet Hyakutake's trajectory through the inner solar system, with a high inclination, passed closest to the earth in late March 1996, passing over the earth's north pole. It was at perihelion on May 1.
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