Wikipedia:Today's featured article/February 4, 2006

From Wikipedia, the free encyclopedia

Comet Hyakutake is a comet that was discovered in January 1996 which passed very close to the Earth in March of that year. It was one of the closest cometary approaches to the Earth in the last 200 years. The comet became very bright in the night sky, and, as a result, it was seen by a large number of people around the world. The comet temporarily upstaged the long-awaited Comet Hale-Bopp, which was approaching the inner solar system at the time, although Hyakutake was only at its brightest for a few days. Scientific observations of the comet led to several notable discoveries. Most surprising to cometary scientists was the discovery of X-ray emission from the comet, the first time a comet had been found to be emitting X-rays. This emission is believed to be caused by ionised solar wind particles interacting with neutral atoms in the coma of the comet. The Ulysses spacecraft also unexpectedly crossed the comet's tail at a distance of more than 500 million km from the nucleus, showing that Hyakutake had the longest tail yet known for a comet. Hyakutake is a long period comet. Before its most recent passage through the solar system, its orbital period was about 15,000 years, but the gravitational influence of the giant planets has now increased this to 72,000 years. (more...)

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