Astronomer, born in Toxteth, Merseyside, NW England, UK. He studied at Cambridge, and was ordained in 1639. He was curate of Hoole, Lancashire, where he made the first recorded observation of the transit of Venus (24 Nov 1639, old dating style) which he had predicted. He showed the Moon's orbit to be approximately elliptical, and calculated an improved value for the solar parallax.
Jeremiah Horrocks (c.1618 – January 3, 1641), sometimes given as Jeremiah Horrox, was an English astronomer who made the first observation of a transit of Venus.
Horrocks was born in Lower Lodge, Otterspool in Toxteth Park, near Liverpool in Lancashire.
At Cambridge, he became familiar with the works of Johannes Kepler, Tycho Brahe, and others. Horrocks was convinced that Lansberg's tables were inaccurate when Kepler predicted that a near-miss of a transit of Venus would occur in 1639. Horrocks believed that the transit would indeed occur, having made his own observations of Venus for years.
Horrocks focused the image of the Sun through a simple telescope onto a piece of card, where the image could be safely observed. From his location in Much Hoole, he calculated that the transit was to begin at approximately 3:00 pm on November 24, 1639 (Julian calendar, or December 4 in the Gregorian calendar).
Horrocks' observations allowed him to make a well-informed guess as to the size of Venus, as well as to make an estimate of the distance between the Earth and the Sun. His figure of 59 million miles (95 Gm, 0.63 AU) was far from the 93 million miles that it is known to be today but it was a more accurate figure than any suggested up to that time. A treatise by Horrocks, Venus in sub sole visa (Venus in transit across the Sun) was published by Johannes Hevelius at his own expense in 1662.
Horrocks returned to Toxteth Park sometime in the summer of 1640 and died suddenly and from unknown causes on the 3 January 1641, aged about 22 years old.
Further reading
Peter Aughton: The transit of Venus: the brief, brilliant life of Jeremiah Horrocks, father of British astronomy.
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