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Why were Edmond Halley’s claims about Aldebaran and Betelgeuse incorrect?
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Edmond Halley
Edmond Halley, detail of an oil painting by Richard Phillips, c. 1720; in the National Portrait Gallery, London.
Edmond Halley’s claims regarding the proper motion of Aldebaran and Betelgeuse were incorrect because he was misled by inaccuracies in ancient star positions.1
In 1718, Halley compared contemporary observations of star positions with data recorded in the Almagest by the ancient Greek astronomer Ptolemy. While this methodology successfully led him to discover the proper motion of Sirius and Arcturus, the data he used for Aldebaran and Betelgeuse contained errors, resulting in his false announcement of their movement.1