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Pluto The search for still more planets continued into the present century. In 1930 an American astronomer named Clyde Tombaugh was successful. He spotted a tiny moving ‘star’ which proved to be the ninth planet, Pluto. It lies so far away that it takes nearly 250 earth-years to circle around the Sun. Pluto was not the most distant planet until this year (1999), but at the moment it is. It was circling inside Neptune’s orbit. We know little about Pluto. It is so distant that it appears only as a speck in telescopes. And no space probes have visited it yet. Pluto is a very tiny world, and is by far the smallest planet. It is much smaller even than our moon. It has a moon of its own, called Charon. Surprisingly, Charon is half as big across as Pluto is. This is why astronomers often call Pluto-Charon a double planet. |
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