20 April

1786: On 20 April 1786, John Goodricke died. He was born in Groningen, the son of a British diplomat and a Dutch merchant's daughter. Profoundly deaf from the age of five, he was the first to notice that some variable stars were periodic (a star changes its brightness at regular intervals when viewed from Earth).

The discovery of variable stars was made by David Fabricius in 1596, when he discovered Mira, a star which changed brightness.

Nearly two hundred years later, John Goodricke studied the star Algol and found that its brightness changed by more than one magnitude over a period of 68 hours and 50 minutes. Goodricke reported this observation in 1783 to the British Royal Society. To explain the phenomenon, he proposed two theories: that the star is periodically occulted by a dark body, or that the star had a darker region which rotated. With his first theory, Goodricke is noted as the discoverer of occultating variable stars.

John Goodricke was admitted to the Royal Society on 16 April 1786, but died of pneumonia four days later without taking his seat. He was 21 years old.