February 4th: Clyde Tombaugh's birthday: Pluto

Astronomer Clyde Tombaugh was born on this date in 1906. He is famous for discovering Pluto, so here are 10 things you may not know about Pluto.

Pluto and its satellites as seen by the Hubble Space Telescope
(Photo by NASA)

1. Tombaugh, who was 23 at the time, identified the object which would become known as Pluto through taking a series of photographs of the night sky and looking at them on a machine called a "blink comparator", so he could more easily make out which object had moved.
2. Pluto is composed primarily of rock and ice; Pluto's atmosphere consists of a thin envelope of nitrogen, methane, and carbon monoxide gases; Pluto's temperature is about 43 K (−230 °C)
3. The name "Pluto" was originally thought of by an 11 year old girl, Venitia Burney, who was interested in classics and astronomy, and thought that the name of the god of the Underworld was appropriate for a world which would be very cold and dark. She mentioned this to her grandfather, who happened to have been a librarian at Oxford's Bodleian Library, and he passed the suggestion on to people with influence.
4. "Pluto" was not the only suggestion. The planetoid could have ended up being called Zeus, Percival, Constance, Minerva or Cronus. Pluto proved by far the most popular choice and was elected unanimously as the best name.
5. In most languages, Pluto is Pluto, but in Hindi and Vietnamese it is called Yama, and in some Polynesian languages, Whiro. These are the Hindu and Maori gods of the Underworld.
6. In 1941, Glenn T. Seaborg named a new element Plutonium after Pluto, following uranium, which was named after Uranus, and neptunium, which was named after Neptune.
7. Pluto has five moons: Charon, discovered in 1978; Nix and Hydra, both discovered in 2005; Kerberos, discovered by the Hubble Space Telescope in 2011; and Styx, discovered in 2012.
8. Pluto takes 248 years to orbit the sun. Its "day" is equal to 6.39 earth days.
9. The orbit of Pluto is erratic - its distance from the sun varies considerably throughout its orbit - at times, so far away that its atmosphere of nitrogen and methane freezes and vanishes. Its orbit crosses that of Neptune, but scientists have concluded that the two will not collide in the foreseeable future - although Pluto's chaotic orbit makes it difficult to predict what Pluto will do after a few million years.
10. In astrology, Pluto is the ruling planet of Scorpio, and represents destroying in order to renew. Pluto governs big business, wealth, mining, surgery and detective work, anything involving digging under the surface to bring the truth to light. Pluto is also associated with the day Tuesday.