Astronomy Picture of the Day

Explanation: Sure, that figure-8 shapedcurve you get when you markthe position of the Sun in Earth's sky at the same time eachday over one year is called an analemma.On the left,Earth's figure-8 analemmawas traced by combining wide-angle digital imagesrecorded during the year from December 2011 through December 2012.But the shapeof an analemma depends on the eccentricity of a planet'sorbit and the tilt of its axis of rotation,so analemma curvescan look differentfor different worlds.Take Mars for example.The Red Planet's axial tilt is similar to Earth's, but its orbit aroundthe same sunis more eccentric (less circular) than Earth's orbit.As seen from the Martian surface, the analemma tracedin the right hand panel is shaped more like a tear drop.The Mars rover Opportunity captured the images usedover the Martian year corresponding to Earth dates July 2006 to June2008.Of course, each world's solstice dates stilllie at the top and bottom of their different analemma curves.The lastMarsnorthern summer solstice was May 29, 2025.Our fair planet's 2025 northern summer solstice is atJune 21, 2:42 UTC.