dipper@utastro.UUCP (Debbie Byrd) (09/26/85)
An astronomer ALMOST made a monumental discovery on this date in 1756. More on the man who almost found the planet Uranus -- after this. September 26 The Man Who Almost Found Uranus A German astronomer could have gone down in history on today's date in the year 1756. At that time, only six planets were known -- and only six planets had ever been known since the dawn of history. But, on this date in 1756, Tobias Mayer saw a seventh planet -- Uranus. Only trouble was, he didn't know what he saw. He recorded Uranus in his catalogue as a fixed star. If he'd just observed it twice within a few days, he'd might have seen it move against the fixed star background. Well, it was 25 more years before William Herschel saw Uranus -- and noticed that it looked like a disk, instead of a pinpoint. Stars always appear as points because they're so far away. But planets are millions of times closer -- and they do look like disks through a telescope. So William Herschel became the first person in recorded history to discover a planet, in the year 1781. You can't really blame Mayer for not realizing the true nature of Uranus. After all, no one had ever discovered a planet, and people didn't imagine that the boundaries of the solar system might extend beyond the outermost known planet, Saturn. When Herschel first discovered Uranus, he thought he'd found a comet. Mayer's was the first of twenty-three prediscovery observations of Uranus. Later, these so-called "ancient" observations were used to chart the orbit of the new planet -- and to determine, among other things, that it takes about 84 of our years to complete one orbit around the sun. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin