C/1995 O1, also known as Hale-Bopp, is a long-period comet that was discovered in 1995 by astronomers Alan Hale and Thomas Bopp. It became one of the brightest comets of the 20th century, visible to the naked eye for a record 18 months. Its orbit takes it around the Sun approximately every 2,533 years. The comet reached its closest approach to Earth on April 1, 1997, and was widely observed and photographed. C/1995 O1 is notable for its large nucleus and two distinct tails, one made of gas and the other of dust, which are characteristic features of many comets.