Jupiter: The Gas Giant

If you look outside tonight, the brightest object you'll see in the southeast sky is Jupiter. If you live in the city, it may be the only thing visible in that area of the sky; you can't miss it. At magnitude -2.7, it's the third brightest object in the night sky next to the moon and Venus (Venus is not currently visible) and will be up for most of the night.

Jupiter is one of the gas giants, composed primarily of hydrogen. It takes less than 10 hours for it to rotate on its axis. The most prominent feature on the planet is the Great Red Spot (GRS), visible in telescopes. You'll see the GRS in the photo below.

Photo courtesy of NASA and the NSSDC
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References:
Wikipedia
Hubble Telescope photos