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Apparent retrograde motion of Mars in 2003. Animation: <a href="http://en.wikipedia.org/wiki/File:Apparent_retrograde_motion_of_Mars_in_2003.gif">Eugene Alvin Villar</a>, Creative Commons, some rights reserved
Apparent retrograde motion of Mars in 2003. Animation: Eugene Alvin Villar, Creative Commons, some rights reserved

Spring comes to the solar system

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St. Lawrence University physicist Aileen O'Donoghue stopped by the NCPR studio this morning with an update on all the ways we can chart the change of season without ever looking at a thermometer. Just watch the winter constellations, like Orion, disappear and the spring sky emerge.

She also maps out where Earth is in relation to the other planets racing around the Sun, and which ones we can see just now. Venus is still bright in the morning. We're moving away from Jupiter, and you'd probably need really good binoculars or a telescope now to see its moons. And Mars is red and bright in the east early in the evening. If you follow its motion night by night, you'll notice it's going "backwards" for a while now. She explains this retrograde motion, which was a key clue in the ancients' realization that we are not the center of the universe.

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Martha Foley
News and Public Affairs Director

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