Comet Hale–Bopp
Comet Hale–Bopp was the most widely observed comet of the 20th century. It was visible to the naked eye for a record 18 months, twice as long as the Great Comet of 1811, the previous record holder. The comet was discovered independently on July 23, 1995, by two observers, Alan Hale and Thomas Bopp, both in the United States. It...