John R. Hager, age 9, of Quincy, Mass., for his question:

Who first saw the planet Pluto?

The Planet Uranus was discovered in 1781, more or less by accident. Until then, people thought the Solar System was complete with six planets. We live on one of them and a normal pair of eyes can pick out Mercury, Venus, Mars, Jupiter and Saturn. But very, very sharp eyes are needed to spot Uranus and they must know just where to look in the sky.

The world was agog at the new‑found planet Uranus. The experts watched and figured out its path around the sun. This path was unusual. Another planet, still farther from the sun, seemed to be pulling at 'Uranus. Two young men, Adams of England and Leverrier of France set out to figure the position of this invisible planet. In 1846, their work resulted in the discovery of Neptune.

Now Neptune was watched and figured. Experts decided that it could not be causing all the strange behavior of Uranus. So the search began for still another planet, even farther from the sun. The most valuable work was done by two Americans, William Pickering and Percival Lowell.

In 1909, William Pickering published a book about his work called "A Search for a Planet beyond Neptune". From 1905 Percival Lowell devoted himself to searching for the distant planet. He used his money to build and endow the Lowell Observatory at Flagstaff, Arizona. In 1915 he published his mathematical findings about the possible position of the invisible planet.

Both men agreed as to the likely position of the distant planet. Lowell estimated it to be seven times the weight of the earth. Pickering estimated it to be twice as much. But neither of these two great men was first to spot the distant planet.

Lowell died in 1916. Pickering went on studying the countless dots on telescopic photographs, trying to pick out the planet beyond Neptune. Somehow, he overlooked it among those thousands of tiny bright dots.

From 1929 the Observatory at Flagstaff was developed to finding the distant planet. On January 21, a young man named Clyde Tombaugh was studying a host of dots on a plate taken by a 13‑inch telescope. One of those dots could be it!  This dot was watched for a few weeks and proved itself to be a planet. The discovery of another planet was announced to the world in March, 1930. It was soon named Pluto, and the first two letters of its name are used in its shortened form. These two letters also stand for Percival Lowell, without whose work and efforts the planet would not have been discovered at that time.

Clyde Tombaugh's discovery sent Pickering back to look at his old telescopic plates. There was the planet Pluto all the time, overlooked in the host of bright dots on the photograph. Still more old plates were examined. The little planet had been appearing in pictures for some time.  But Clyde Tombaugh was the first person to pick it out from all the other tiny dots of light scattered over the sky pictures.