Can astronomers kick a planet out of our solar system? Clyde Tombaugh, 90, discovered the planet Pluto in 1930. But some scientists now think Pluto is not a true planet. "I'm plain not going to listen to them," Tombaugh says.
This month astronomers saw photos of Pluto taken by the Hubble Space Telescope. The pictures show frozen gases sweeping across Pluto's surface. These photos have added to old doubts about Pluto's planethood. "It's not the same as other planets," says Larry Esposito of the University of Colorado. "It's too small; it has too much ice."
Astromathematician Percival Lowell first calculated Pluto's presence in the solar system in 1905. He called it Planet X. Tombaugh then became the first to actually spot the planet in space photos. "It was the thrill of my lifetime," he says. The planet was named Pluto, after the Greek god of the underworld, by Venetia Burney, 11, of England.
Pluto is smaller than the earth's moon. It is 3.7 billion miles from the sun and gets as cold as minus 380 degrees Fahrenheit. "It's like an icy little dwarf on the outskirts of the solar system," says Anne L. Kinney of the Space Telescope Institute in Baltimore, Maryland.
Some think Pluto may have been a comet that got sucked into the sun's gravitational pull. But Tombaugh insists his planet is a planet. "Kids will be very upset if we demote it," he says. "It's a little planet, and kids are little. They have a lot in common."