This composite of images spaced about a week apart - from late July 2005 (bottom right) through February 2006 (top left) - traces the retrograde motion [
http://www.lasalle.…retrograd.html ] of ruddy-colored Mars [
http://antwrp.gsfc.…] through planet Earth's night sky. On November 7th, 2005 the Red Planet was opposite the Sun in Earth's sky (at opposition [
http://antwrp.gsfc.…]). That date occurred at the center of this series with Mars near its closest and brightest. But Mars didn't actually reverse the direction of its orbit to trace out [
http://www.astro.ui…] the Z-shape. Instead, the apparent backwards or retrograde motion with respect to the background stars is a reflection of the motion of the Earth itself. Retrograde motion can be seen [
http://antwrp.gsfc.…] each time Earth overtakes and laps planets orbiting farther from the Sun, the Earth moving more rapidly through its own relatively close-in orbit. The familiar Pleiades [
http://antwrp.gsfc.…] star cluster lies at the upper left.
Explanation
This composite of images spaced about a week apart - from late July 2005 (bottom right) through February 2006 (top left) - traces the retrograde motion [
http://www.lasalle.…retrograd.html ] of ruddy-colored Mars [
http://antwrp.gsfc.…] through planet Earth's night sky. On November 7th, 2005 the Red Planet was opposite the Sun in Earth's sky (at opposition [
http://antwrp.gsfc.…]). That date occurred at the center of this series with Mars near its closest and brightest. But Mars didn't actually reverse the direction of its orbit to trace out [
http://www.astro.ui…] the Z-shape. Instead, the apparent backwards or retrograde motion with respect to the background stars is a reflection of the motion of the Earth itself. Retrograde motion can be seen [
http://antwrp.gsfc.…] each time Earth overtakes and laps planets orbiting farther from the Sun, the Earth moving more rapidly through its own relatively close-in orbit. The familiar Pleiades [
http://antwrp.gsfc.…] star cluster lies at the upper left.
Explanation
