Halley's Comet is a periodic comet that can be seen from Earth every 75-76 years. It was first observed by English astronomer Edmund Halley in 1705 and is named after him. The comet is composed of ice, dust, and rock, and its nucleus is estimated to be between 6 and 15 kilometers in diameter. Halley's Comet has been observed during its last eight appearances, most recently in 1986. Its next appearance will be in 2061.