Experienced stargazers live by the adage that you never know what you’ll find in the night sky until you look. Perhaps the best example of this was the accidental discovery of the planet Uranus by William Herschel on March 13, 1781.
Herschel was one of history’s greatest stargazers, but he didn’t start out as a scientist. He came from a musical family and became a professional musician and composer, moving to England from his native Germany and securing a lifelong appointment as an organist in Bath. But he grew bored and looked for a new challenge.
So he turned to astronomy. He quickly mastered the layout of the night sky, but he was disappointed with the small-aperture refractors of the day. Herschel started to construct his own reflecting telescopes, eventually building some 400 instruments.
With his homemade 6” reflector, Herschel noticed an object near the star zeta Tauri on March 13, 1781. The object presented a small disk which, unlike a star, appeared to increase in size with magnification. Over the next four nights, Herschel noticed the object had moved slightly against the background stars like a comet, yet it had no tail. Additional sightings by other astronomers led to the conclusion that Herschel had discovered a new planet.
The planet was first called “George’s Planet” and “George’s Star” after the English king. The name of Uranus was chosen by the German Johann Bode in honor of the Greek god of the sky. Uranus remains the only major planet, other than Earth, not directly named after a Roman god.
The discovery of Uranus gained Herschel fame and freedom. He was granted fellowship in the Royal Society and was propelled into a career as a professional astronomer with the help of a rich stipend from King George III, himself a dedicated amateur astronomer. Herschel eventually charted thousands of galaxies, nebulae, stars, and star clusters. But he never lost his love “for this magnificent collection of stars” in which we live. He observed and charted the heavens nearly until his death at age 83.
Today, 234 years after its discovery, Uranus lies low on the western horizon after sunset along with the planet Mars and brilliant Venus. It’s barely visible in binoculars and is moving towards conjunction with the Sun early next month before it reappears in the morning sky.