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  Image of Comet Hale-Bopp taken by Wally Pacholka on April 5, 1997 from the Joshua Tree National Park in California.

On July 23, 1995, an unusually bright comet outside of Jupiter's orbit (7.15 AU!) was discovered independently by Alan Hale, New Mexico and Thomas Bopp, Arizona. The new comet, designated C/1995 O1, is the farthest comet ever discovered by amateurs and appeared 1000 times brighter than Comet Halley did at the same distance. Normally, comets are inert when they are beyond the orbit of Jupiter, so it has been speculated that Comet Hale-Bopp is either a rather large comet or experienced a bright outburst (or both). The comet was the brightest comet since Comet West in 1976. From Hubble Space Telescope images, the comet's diameter has been determined to be about 40 km. The Pic du Midi Observatory has ascertained from their observations that the comet's rotation rate is 11.4 hours.

Comet Hale-Bopp image taken by Loke Kun Tan on March 30, 1997 from the Red Rock Canyon Park in California.

Comet Hale-Bopp made its closest approach to Earth on March 22, 1997 at a distance of 1.315 AU (1 AU = 93 million miles or 150 million km). It reached perihelion (closest distance to the Sun) on April 1, 1997 at 0.914 AU. The comet did not pass particularly close to either the Sun or the Earth, but because of its rather large size, the comet was very bright and reached a peak magnitude of about -1. In fact, Comet Hale-Bopp was at magnitude 0 or brighter for an astounding 8 weeks, the longest ever recorded for a comet. Also, Comet Hale-Bopp holds the record for the longest period of naked eye visibility, an astoninshing 19 months, easily breaking the the previous record of 9 months held by the Great Comet of 1811.


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