Jan 12, 2005

Saturn, all night long


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On Thursday, January 13th, Saturn will be 750 million miles from Earth--the closest we get to the ringed planet this year.





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January 12, 2005: When the sun sets on Thursday, January 13th, a golden star will rise in the east. Soaring overhead at midnight, it will be up all night long, beautiful and eye-catching.




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That "star" is Saturn.

January 13th is a special date for Saturn because that's when it is closest to Earth: only 750 million miles away, compared to a maximum distance of almost a billion miles. This makes the ringed planet unusually big and bright.

An astronomer would say "Saturn is at opposition" because Saturn and the sun are on opposite sides of the sky. Earth and Saturn are closest together at opposition; see the figure below. The sun, Earth and Saturn are lined up in a straight line with Earth in the middle. This happens every 13 months, approximately. The 2005 opposition of Saturn is so perfect that, if you were on Saturn, you would see Earth transiting the face of the Sun.


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Left: Earth and Saturn are closest together when Saturn is "at opposition." The red circle is Saturn's orbit; the blue Earth's.

To find Saturn, step outside around 7:30 p.m. local time and face east. The planet is easy to see almost halfway up the sky next to Castor and Pollux in the constellation Gemini.

Got a telescope? Point it at Saturn. Even a small department-store 'scope will show the planet's rings. They are breathtaking. You might also notice a little pinprick of light near Saturn. That's Titan, Saturn's largest moon.

The European Space Agency's (ESA's) Huygens probe will attempt to land on Titan on January 14th. With hypothesized methane rain, gasoline seas, hot lightning and icy mountains, Titan could be the weirdest world in the solar system. Or not. No one knows because dense orange clouds hide the giant moon's surface. If Huygens survives its bold descent, we'll soon find out what's down there. Good luck ESA!


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Above: A map of the evening-eastern sky in mid-January 2005. [



If bad weather spoils your view on January 13th, don't worry. Saturn will remain close to Earth, receding slowly, all month long. You can find it any evening in the eastern sky next to Castor and Pollux. January 23rd is especially good because the full moon will glide right past Saturn, marking its location for all to see.

Bright, golden, ringed, breathtaking: Saturn. It's worth a look.