Greg Redding, age 10, of Moomesville, Ind., for his question:

CAN YOU TELL ME ABOUT PLUTO?

Pluto is a small, dark world. It is on the edge of our solar system with an orbit several billion miles from the sun. It is the ninth planet out from the sun, and so far away from it that it is a cold spot where it is always night. The sun in Pluto's sky can be no more than a bright spot.

Pluto is almost invisible from earth. Only a high¬powered telescope can bring the planet into our view, and even then it is small and dim. Seventh and eighth planets out from the sun are Uranus and Neptune. Astronomers had been plotting their orbits and discovered they did not travel at their expected speeds. Something was affecting them, and astronomers wondered if it might not be a gravitational pull from a ninth planet.

Percival Lowell, an American astronomer, took on the task to find the mystery planet. By 1905 he was sure that he was looking for a small planet some 4 billion miles from the sun. But Lowell died before the planet could be located.

Another American astronomer, this one named Clyde Tombaugh, took up the task of finding the planet. Working with telescope and camera, he photographed the sky, comparing changes and a shifting point of light.

In February, 1930, Tombaugh found a spot of light that moved. It proved to be the unknown planet  named Pluto after the god of darkness. All agreed that the name was an excellent one since it was a planet of night. Also, the first two letters of the new planet's name were the initials of Percival Lowell.

Astronomers think Pluto is about half the size of the earth. They see it as a dim, yellowish dot without markings. It does not appear to have moons, and it spins once every six and a half earth days. It probably has a temperature of about minus 350 degrees Fahrenheit. If it has an atmosphere, it must be frozen.

Some astronomers think that Pluto was not born a planet, but that perhaps it had once been a moon that circled Neptune. They believe that it then broke away from its planet and began to orbit the sun, thus become a planet itself.

Still a mystery is Pluto's pull on Uranus and Neptune. That is why some astronomers think there may be a tenth planet orbiting in the dark.

Recently the planet Pluto was classified as a non planet.

        For latest information on PLUTO go to Science News in YouAskAndy main menu and click on             NASA Jet Propulsion Laboratory