Science: Pluto's Day

Astronomers are cosily familiar with stars quadrillions of miles from the earth, and with galaxies much more distant. But Pluto, a member of the sun's own planetary family, and only 3½ billion miles away, has little personality for them. The outermost member of the solar system, it shines only feebly by reflected sunlight. Even in the biggest telescopes it looks like a faint star; only its motion among the real stars and a slight fuzziness prove it to be a planet. Astronomers are not sure how big it is (probably midway between Mercury and...

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