Halley’s Comet is named after Edmond Halley (1656-1742), born in Middlesex, who was the first to calculate that it returned in an orbit visible from Earth every 75 to 76 years. One of its famous appearances was in 1066, just before the invasion of Britain by William the Conqueror (c.1028-87 and a.k.a. William the Bastard or William of Normandy). He took it to be a sign of success and it was shown on the Bayeux Tapestry. The comet’s next appearance to the naked eye on our planet will be in 2061.
Edmond Halley published his theory in 1705. Before that, people thought each sighting was of a different comet rather than the same one coming back.
(Image: NASA Universe at Flickr.com / CC BY 2.0)