Uranus at Opposition

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The planet Uranus is putting in its best appearance of the year right now. It rises at sunset and remains in the sky all night. It's also closest to us for the year, so it shines brightest. Unfortunately, though, you still need binoculars to find it.

Uranus is one of the giants of the solar system -- only Jupiter and Saturn outrank it. But Uranus may be put together differently from those bigger siblings.

Jupiter and Saturn are balls of hydrogen and helium gas wrapped around solid cores. Uranus probably has a solid core, too, but it has a lot less hydrogen and helium.

All the hydrogen and helium it does have are contained in an atmosphere that's perhaps 3,000 miles thick -- about one-fifth of the distance down from the planet's cloudtops.

Below that may be a liquid or partially frozen mixture of water, methane, and rocky minerals. Unlike the boundary between the oceans and air here on Earth, though, there probably isn't a sharp boundary between the layers of Uranus. The pressure is so great that the liquid and gas merge in a slushy transition zone.

Uranus climbs into view in the southeast after nightfall, at the eastern edge of Aquarius. Through binoculars, it looks like a faint blue-green star. It's far to the left of the Moon tonight, but will stand just below the Moon on Sunday night. That'll help you find it, although the best view of Uranus itself comes a few nights later, after the bright Moon moves out of the way.

Script by Damond Benningfield, Copyright 2004, 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.