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Jupiter in Retrograde Motion

Jupiter in Retrograde Motion

   Today at 7 UT (1 am CST) the outer planet Jupiter became stationary in its eastward orbital motion around the Sun. It will now begin moving backward toward the west. This reversal in motion is known as retrograde motion and is something that occurs to varying amounts as the Earth passes by each outer planet.
   The Earth passing by an outer planet is a result of the Earth having a faster orbital speed, and as the angles between Earth and an outer planet change there is the appearance of the outer planet slowing down and stopping its regular eastward motion. Then for a time ranging from a week or so to several months the outer planet appears to be moving backward or toward the west. After a time the planet resumes its eastward motion.
   Below is a short list with the Right Ascension (RA) and Declination (Dec) for Jupiter every 10 days showing the changing position of Jupiter during its period of retrograde motion. RA increases in value as a planet orbits toward the east and decreases in value during retrograde motion. Using the free equatorial star chart downloaded from the Stephen F. Austin Observatory the position of Jupiter could be plotted as the retrograde motion occurs. The last column shows the Jupiter to Earth distance in Astronomical Units (AU).

Date     RA       Dec     Distance
Nov  6  7 28   + 21 51   4.6996051
Nov 16  7 28   + 21 54   4.5643608
Nov 26  7 26   + 21 59   4.4447808
Dec  6  7 23   + 22 07   4.3456108
Dec 16  7 18   + 22 17   4.2713962
Dec 26  7 13   + 22 28   4.2255230
Jan  5  7 07   + 22 39   4.2104464
Jan 15  7 01   + 22 49   4.2271619
Jan 25  6 56   + 22 58   4.2748290
Feb  4  6 51   + 23 05   4.3514587
Feb 14  6 48   + 23 10   4.4536150
Feb 24  6 46   + 23 14   4.5769570
Mar  6  6 45   + 23 16   4.7169518
Mar 16  6 46   + 23 16   4.8685936
Mar 26  6 48   + 23 14   5.0271761
Apr  5  6 51   + 23 11   5.1884131

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

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