Astronomy Picture of the Day

Explanation: This composite of images spaced a weather-permitting 5 to 9 days apart,from 2024 September 19 (top right)through 2025 May 18 (bottom left), faithfully tracesruddy-colored Marsas it makes a clockwise loop through the constellations Gemini and Cancer inplanet Earth's night sky.You can connect the dots and dateswith your cursor over the image, but be sure to check outthis animation of theRed Planet's 2024/25 retrograde motion.Of course Mars didn't actually reverse the direction of its orbit.Instead, the apparent backwards motion with respect to the backgroundstars is a reflection of the orbital motion of Earth itself.Retrograde motioncan be seen each time Earth overtakesand laps planets orbiting farther from the Sun, theEarth moving more rapidly through its own relatively close-in orbit. In this caseMars' apparent eastward motion began to reverse around December 8,when it seemed to linger nearopen star cluster M44 in Cancer.After wandering back to the west, under Gemini's bright starsCastor and Pollux, Mars returned to pose near M44 by early May.At its brightestnear oppositionon 2025 January 16, Mars was a mere96 million kilometers away.