February 18 - Discovery of Pluto

This Day in History: 18 February 2020

 

18 February 1930

 

30 years ago, today, Pluto was discovered by astronomer, Clyde W. Tombaugh, at the Lowell Observatory in Arizona. The existence of a ninth planet in our solar system was first proposed by Percival Lowell, who searched a decade for the planet, with no success. In 1929, however, his calculations were used as a guide, and the search for this mysterious planet was resumed in Arizona, and on this day, Tombaugh discovered the tiny planet. Using a new astronomic technique of photographic plates combined with a blink microscope, he spotted Pluto. This finding was eventually confirmed by several others, and the discovery was publicly announced on March 13, 1930.

 

Pluto was appropriately named after the Roman God of the underworld, also known as Hades, in Greek mythology, after its surface temperatures of approximately -360 Fahrenheit. It is nearly 4 billion miles away from the sun and takes around 248 years to complete a full orbit. After its discovery, some astronomers questioned Pluto's effect on Uranus and Neptune, and after the discovery of Pluto's only moon, Charon, it was thought that the two formed a double-planet system to affect Uranus and Neptune. In August 2006, it was announced by the International Astronomical Union that Pluto would be no longer considered a planet, as its oblong orbit overlapped Neptune's, and thus did not meet the new criteria.

 

Want to find out more about the characteristics of Pluto, and also more about its discovery? Click here for more details.