Also called the Great Comet of 1997, comet C/1995 O1 (Hale-Bopp) is a large comet with a nucleus measuring approximately 37 miles (60 kilometers) in diameter. This is about five times the size of the object hypothesized to have led to the demise of the dinosaurs. Due to its large size, this comet was visible to the naked eye for 18 months in 1996 and 1997.
It takes about 2,534 years for Hale-Bopp to orbit the sun once. Hale-Bopp last reached perihelion (closest approach to the sun) on Apr. 1, 1997.
Comet C/1995 O1 (Hale-Bopp) was discovered on July 23, 1995, independently, by both Alan Hale and Thomas Bopp. Hale-Bopp was discovered at the amazing distance of 7.15 AU. One AU is equal to about 150 million km (93 million miles).
Comets are usually named for their discoverer(s) or for the name of the observatory/telescope used in the discovery. Since both Alan Hale and Thomas Bopp discovered this comet it is named for them. The letter "C" indicates that C/1995 O1 (Hale-Bopp) is a long-period comet and is not expected to return to the inner solar system. 1995 indicates the year of discovery.