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W. Applebaum (Illinois Institute of Technology)
Horrocks's importance in the history of astronomy has long been recognized. Working shortly after Kepler's death, he was among the earliest to adopt Keplerian astronomy, and went on to improve the Rudolphine Tables. His lunar theory was the most advanced of his time, its importance acknowledged by Newton. He is perhaps best known as the first to predict and observe a transit of Venus, which, along with other observations led him to improve planetary parameters and the solar parallax. Although his work was discovered only a decade after he died, it was deemed significant enough for Hevelius to publish Horrocks's treatise on the transit, and for the Royal society to publish most of his surviving manuscripts.
With the approach of the transit of Venus next June, just over 120 years after the last one, it is appropriate that we celebrate Horrocks's achievement in his observation of the transit of 1639. In the fall of that year Horrocks discovered, contrary to the best tables of the day (Kepler's) that the rapidly approaching conjunction would see Venus on the face of the Sun.
Horrocks notified three others, and prepared himself, using accounts he had read in Kepler, an account of Gassendi’s observation of the transit of Mercury of 1631, and his own effort to observe a Mercury transit. Only he and his friend William Crabtree were able to observe the transit for the 15-20 minutes between its entry on the Sun and sunset. Horrocks then spent the next year writing several drafts, all of which were incomplete, when he died in January 1641.
The author(s) of this abstract have provided an email address for comments about the abstract: applebaum@iit.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.