Discovery of Pluto
Next: February 18, 2027
A tiny dot that moved.
The story
Where it comes from
This Story marks the anniversary of 18 February 1930, when Clyde Tombaugh, a 24-year-old Kansas farm boy working at Lowell Observatory in Flagstaff, Arizona, found Pluto. For weeks he had compared pairs of photographic plates of the night sky using a 'blink comparator', which flipped rapidly between two images to reveal anything that moved. Around 4 pm, blinking plates taken on 23 and 29 January, he spotted a faint dot that had shifted. He walked to the director's office and said, 'I have found your Planet X.'
How it's celebrated
There is no formal observance, but Lowell Observatory, which still keeps the discovery plates in its archives, welcomes visitors to the Flagstaff hill where Pluto was found. Anyone can mark the day by looking at the close-up images NASA's New Horizons sent back from Pluto, or by stepping outside on a clear night to think about how small a dot in the sky can be and still be a world.
Did you know
- The name Pluto was first suggested by Venetia Burney, an 11-year-old girl in Oxford, over breakfast with her grandfather in March 1930.
- When NASA's New Horizons flew past Pluto on 14 July 2015, it carried a small canister of Tombaugh's ashes.
- The name used in Japanese and Chinese, 冥王星, 'star of the king of the underworld', was proposed by the Japanese writer on stars Nojiri Hōei in October 1930.
Coming up next
- Copernicus's Birthday · February 19, 2027
- Lantern Festival · February 20, 2027
- World Pangolin Day · February 20, 2027
- World Day of Social Justice · February 20, 2027
- International Mother Language Day · February 21, 2027
- World Thinking Day · February 22, 2027