Comet Hale-Bopp: First spied in 1995, Comet Hale-Bopp may have been the most viewed comet in recorded history. The comet holds the record for the longest period of viewing with the unaided eye: an astonishing 19 months. It will not appear again for another 2,400 years.
Comet Swift-Tuttle, 1992: This comet was first seen in July 1862. As Comet Swift-Tuttle moves closer to the Sun every 120 years, it leaves behind a trail of dust debris that provides the ingredients for a spectacular meteor shower called the Perseids, seen in July and August.
Comet Hyakutake: First discovered in 1996 by a Japanese amateur astronomer, Comet Hyakutake had one of the longest tails ever observed. The Hubble Space Telescope studied the nucleus of this comet in great detail. Its orbit will not bring it near the Sun again for about 14,000 years.
Comet Halley: Comet Halley is perhaps the most famous comet in history. It was named after British astronomer Edmund Halley, who calculated its orbit. He determined that the comets seen in 1531 and 1607 were the same objects that followed a 76-year orbit. Comet Halley will return to the inner solar system in the year 2061.
Comet Shoemaker-Levy 9: This comet was discovered in 1993. Between July 16 and July 22, 1994, more than 20 fragments of Comet Shoemaker-Levy 9 collided with the planet Jupiter. The Hubble Space Telescope took many spectacular pictures of this event as the comet's pieces crashed into Jupiter's southern hemisphere. It was the first collision of two solar system bodies ever to be recorded.