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Uranus at Opposition

September 28, 2012

One of the giant worlds of the solar system is putting on its best showing of the year right now. It rises at sunset, remains in the sky all night long, and shines brightest for the year, too. And for the next couple of nights it appears close to the Moon.

Unfortunately, though, the planet Uranus is so far and faint that you still need binoculars and a starchart to find it.

Uranus is the third-largest planet in the solar system — about four times the diameter of Earth. On average, though, it’s about 1.8 billion miles away, so it’s a mere speck in the night sky.

In fact, under especially dark skies it’s just bright enough to see with the unaided eye. Yet no one realized that tiny speck of light was a planet until 1781, when William Herschel observed it through a telescope for several nights. It turns out that others did see it before then, and even charted it. But none of them watched it long enough to see that it moves against the background of stars, so they thought it was a star.

Even then, it’s certain that many people saw Uranus well before the invention of the telescope. Yet it’s so inconspicuous that no one paid any attention to it — not realizing they were looking at one of the worlds of the solar system.

Uranus rises well to the lower left of the Moon tonight, and quite close to the lower right of the Moon tomorrow night — the night of the Harvest Moon, by the way. We’ll have more about that tomorrow.


Script by Damond Benningfield, Copyright 2012

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