Likely the most widely observed comet of the 20th century, Hale-Bopp—named for American astronomers Alan Hale and Thomas Bopp—was visible to the naked eye for a record 18 months, observable even from large cities with light-polluted skies. The comet's passage excited stargazers but also incited various conspiracy theories. The notion that it was followed by an alien spacecraft inspired a mass suicide among members of the Heaven's Gate cult. When will Hale-Bopp return to the inner solar system? Discuss (http://forum.thefreedictionary.com/postst55597_Hale-Bopp-Comet-Makes-Closest-Approach-to-Earth--1997-.aspx)