What is the distance from the Sun to the Earth for each month of the year?

We all know that Earth orbits our sun in an elliptical path, which means that for certain times of the year it is closer to the sun than for others. Here is a distorted view of the basic orbit, but beware that the scales are all wrong. There is only a 5 million kilometer difference between the longest and shortest lengths of the ellipse!

According to the 1996 US Ephemeris, on the 21st of each month, the distance to the Sun is:


January             0.9840       147,200,000
February            0.9888       147,900,000
March               0.9962       149,000,000
April               1.0050       150,300,000
May                 1.0122       151,400,000
June                1.0163       152,000,000
July                1.0161       152,000,000
August              1.0116       151,300,000
September           1.0039       150,200,000
October             0.9954       148,900,000
November            0.9878       147,700,000
December            0.9837       147,200,000


where the first column gives the distance in Astronomical Units so that 1.0 AU = 149,597,900 kilometers By the way, I have rounded all of the distance numbers to 4 significant figures. If you want a mathematical formula that gives you the distances in AU using these table entries for month number N, it looks like this:

d(N) = 1.0000 + 0.0163 cos [ (2pi/12)*((N-1)/12) + 200*2pi/360]

As you can see from the table, the Earth is farthest from the Sun when the Northern Hemisphere is in the summer season (July 3), and closest in the winter (January 3). If you were living in the Southern Hemisphere, the seasons are reversed so that in the summer, the Sun is closest and in the winter it is farthest.

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