Monday Bites: It's A Planet!

Monday Bites: It's A Planet!

Credit: NASA  

The discovery of Uranus was one of those happy accidents. It was March 13, 1781. Sir William Herschel, the great astronomer of great astronomers, was rapidly progressing on his list of cataloging all the 8th magnitude stars (stars too faint to be seen with the unaided eye). While at it, near the star Zeta Tauri, Herschel came across a curious stellar orb. He couldn't recall ever seeing a star in Taurus, and that too with some nebulosity around it. Upon increasing his telescope's magnification, Herschel observed that the star became more diffuse while the background stars maintained their familiar appearance. 

Herschel thought he was looking at a comet. Only two kinds of celestial objects grow in size upon increasing telescopic magnification — planets or comets. Since no one had previously thought of discovering a planet, William Herschel, a diligent astronomer, settled on the second alternative; perhaps in the back of his mind, he was likely aware of the possibility. Four days later, on March 17, having found that his comet had changed its position relative to the background stars, he became confident in his take. Herschel communicated his discovery to the Philosophical Transactions, Royal Society of London, and the paper was read on April 26, 1781.  

His contemporary astronomers rushed to verify Herschel's claim. 

Nevil Maskelyne, the Astronomer Royal, shared his opinion that Herschel's comet seemed more likely to be a planet than a comet as it didn't have any tail or a coma. By 1783, based on the observations performed by the best of the astronomers, Anders Johan Lexell and Johann Elert Bode, Herschel was convinced beyond reasonable doubt that he had indeed discovered a planet. 

When asked to name his planet, Herschel suggested Georgium Sidus or George's Star to honor his new patron, King George III. However, the name George's Star was unpopular outside England. For some 70 years, the seventh planet had many names and none. Finally, in 1782, Johann Elert Bode suggested that the planet be named Uranus, a Latinised version of Ouranos, the Greek God of the Sky. He argued that since all the planets, Mercury to Saturn, have been named after divinities, it will be better to go with the tradition.