a comet with a period averaging 76 years. In this century it was visible to terrestrial observers just before and after reaching perihelion in 1910 and again in 1986.
Origin: named after Edmund Halley, who first predicted its return
Pronunciation note The common pronunciation for both the comet and the astronomer after whom it is named is /ˈhæli/Show Spelled[hal-ee]Show IPA. This is the pronunciation usually recommended by astronomers. However, several variant spellings of the name, including Hailey, Haley, and Hawley, were used interchangeably during the astronomer's own time, a period when spellings even of proper names were not yet fixed, and corresponding pronunciations have survived. The pronunciation /ˈheɪli/[hey-lee] in particular remains associated with Halley's comet ; it is less likely to be heard as a pronunciation of Edmund Halley .
Halley's comet (hāl'ēz, hā'lēz) Pronunciation Key
A short-period comet that orbits the Sun once every 76 years. It is visible to the unaided eye and last appeared in 1986, when close observation by spacecraft showed that its nucleus measures about 16 km (10 mi) by 8 km (5 mi) and is composed of water ice, stony minerals, and organic compounds. Its next appearance will be in the year 2061.