Short answers, pulled from the story.
Jeremiah Horrocks (1618-1641) was an English astronomer who made three major contributions before his death at twenty-two. He was the first to demonstrate that the Moon moves in an elliptical orbit, the only person to predict the 1639 transit of Venus, and one of the first to suggest that gravity acted between distant bodies. Newton later acknowledged his work in the Principia.
On the 24th of November 1639 (Julian calendar), Horrocks observed the black disc of Venus crossing the Sun from his location in Much Hoole, Lancashire. He first saw it at around 3:15 pm and watched for half an hour until the Sun set. His friend William Crabtree observed the same event from Broughton near Manchester; they were the only two people in the world to witness it.
Horrocks was born at Lower Lodge Farm in Toxteth Park, a former royal deer park near Liverpool, Lancashire. He matriculated at Emmanuel College, University of Cambridge, in 1632 as a sizar, where he studied the works of Kepler and Tycho Brahe, but left in 1635 without graduating.
Venus in sole visa, meaning Venus seen on the Sun, is the treatise Horrocks wrote about his 1639 transit observations. It was published posthumously by Polish astronomer Johannes Hevelius at his own expense and caused great excitement when presented to the Royal Society in 1662, roughly twenty years after it was written. The work included original poetry, humorous passages, and Horrocks's defence of scientific determinism against theological objections.
Horrocks used his observations of the 1639 transit of Venus to estimate the Earth-Sun distance, now known as the astronomical unit. His figure was 95 million kilometres, compared to the accepted value of about 150 million kilometres. It was, however, more accurate than any estimate that had been made before his.
Horrocks died suddenly on the 3rd of January 1641, at the age of twenty-two, in Toxteth Park. Memorials include a plaque in Westminster Abbey, a named lunar crater, stained-glass windows and a marble tablet at the Parish Church of St Michael in Much Hoole installed in 1859, the Jeremiah Horrocks Observatory built at Moor Park in Preston in 1927, and a sculpture by Andy Plant installed at the Pier Head in Liverpool in 2011.