BellaOnline Forums Education Astronomy American astronomer discovered Pluto 85 years ago

American astronomer Clyde Tombaugh (1906-1997) discovered Pluto on February 18, 1930. He used a blink comparator to help him study the sky. This lets you view two photographs taken of the same area of sky several days apart. It “blinks” rapidly between them, helping you to see anything that has moved during that time. Tombaugh is demonstrating the blink comparator in this picture.

I found a digital copy of the two photographic plates on which Tombaugh found the object that had moved. Everyone assumed that it was the giant plant that Perceval Lowell had sought which was disturbing the orbit of Neptune. But it became obvious that Pluto was no giant. Although it's no longer considered the 10th planet, it is first among a new category of heavenly bodies, the Kuiper Belt Bodies. Click here for the story of Pluto's discovery.

The New Horizons mission to Pluto was launched nine years ago, and it's finally due to make its closest pass to Pluto and Charon in mid-July. But it's recently got close enough to be able to image two of Pluto's tiny moons, Nix and Hydra. The link is to an animation of a series of pictures taken by New Horizons. There are squares shown around the little moons so that you can see clearly that they are moving.

For 28 years after its discovery Pluto's moon Charon was an only satellite. But on February 22, 2006 two new moons were discovered, using the Hubble Space Telescope. They are quite tiny. Nix (classical spelling: Nyx) is the Greek goddess of the night and mother of Charon. Hydra was one of the mythological guardians of the Underworld, a 9-headed serpent.