Halley's Comet

Halley's comet, a periodic comet usually appearing every 76 years, is named after English astronomer Edmond Halley (1656-1742), the first person to accurately predict the return of a comet. This famous comet follows a retrograde (east-west), elliptical orbit, providing a magnificent, astronomical spectacle. In 1910, Earth passed through its brilliant, fan-shaped tail which soared 99 million mi (160 million km) into space. During its last apparition (appearance) in 1986, space probes and ground-based technology gathered valuable scientific data on its size, shape, and composition. In 2024, the comet will reach aphelion (furthest point from the Sun) millions of miles outside Neptune's orbit, make a U-turn, and begin its thirty-first observed return to perihelion (point nearest the Sun) inside the orbit of Venus, arriving in 2061. Observed by Chinese astronomers in 240 B.C. and maybe even 466 B.C., Halley's Comet may make 3,000 more revolutions and live another 225,000, if recent estimates calculated from data collected by the space probe Giotto are correct.