"Mars Marches Forward Once Again"

Scheduled air date: 2003 Sep 22-28

Special Note: This topic does not correspond to this week's episode of Star Gazer, which does not describe a specific astronomical event.


As we recently passed by the planet Mars, it was appearing to move opposite its normal direction.  This retrograde motion occurs for a couple of months each time we pass by the red planet, about every 2.2 years.  Now that we've moved away from Mars, its apparent motion has slowed, and will switch directions again on September 27th.  Mars will then resume its usual forward motion.

Mars also appears to pass near the gas giant planet Uranus over the next few weeks.  They appear closest at just over 3.5 degrees on October 7th (though they are separated by 2.8 billion km/1.7 billion miles!).  To aid in identifying Uranus, two stars of similar brightness have been labeled above—SAO 164910 at magnitude 5.4 and SAO 165044 at magnitude 5.8 (the same brightness as Uranus).

(The above field approximates that seen in a typical pair of binoculars; the blue circle in the center is one degree in diameter—about twice the apparent size of our Moon—and is included for scale only.  The positions of Mars and Uranus are shown every three days from September 6th through October 21st.)

If you wish to view illustrations for other episodes, please see our Star Gazer Illustrated directory.


Illustrations on this page were created using TheSky Astronomy Software, an advanced desktop planetarium program designed for Windows.

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