Sunday February 21st the innermost planet Mercury reaches aphelion, its furthest distance from the Sun, 0.4667 AU, (69,817,326 km; 43,382,475 miles). Interestingly, I suppose, is that the next time Mercury reaches aphelion will be May 19th, 10 days after the Mercury transit of the Sun.
All planets orbit the Sun with an orbital shape that is not circular but rather elliptical. How much away from being a circle is called eccentricity of an orbit. With 0 representing a circle and 1 a straight line Mercury, with an eccentricity of 0.2056, has the greatest eccentricity of the other 7 planets. The dwarf planet Pluto, for comparison, has an eccentricity of 0.2488.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.