You Can See Halley's Comet Twice, If You're Lucky
Halley's Comet is named after astronomer Edmond Halley, who was the first person to correctly identify the comet and predict its return. The comet had been documented for thousands of years, however. In fact, the first known observation of the comet occurred in 239 BC. Later, it would appear in 1066, just before William the Conquerer's invasion of England. A depiction of the comet was woven into the Bayeux Tapestry, and some say that William viewed its coming as a prophecy of his success.
Crash course in comets, a balanced mixture of ice and rock.
from Crash Course
Key Facts In This Video
Comets are a mixture of ice and rock, unlike asteroids, which are mostly rock. (1:26)
Comets with orbital periods of less than 200 years are called short-period comets. (4:35)
See Giotto's detailed pictures of Halley's Comet from 1986: (6:52)
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