How fast does the Earth go at perihelion and aphelion? (Intermediate)

I need to find the approximate speeds of the earth's orbit at perhilion and aphelion (this year, for example, if it makes a difference). I have given myself a crash course in astronomy over the course of the last three months and command a fair if somewhat pedantic understanding of the underlying principles. The earth's mean revolutionary velocity is easily found, but i have not found these precise figures and am not much of a math whiz. Can you help me?

The formula for the velocity of an object at some distance r from the Sun is:

v = sqrt[GM*(2/r - 1/a)]

Where G is the universal gravitational constant, M is the mass of the Sun, and a is the planet's semimajor axis.

At perihelion, Earth's distance from the Sun is r=a(1-e) and at aphelion, it's r=a(1+e).

G=6.673*10-11 N m2/kg2

M=1.989*1030 kg

a=1.496*1011 m


So plugging in the numbers, the speed at perihelion is 30,300 m/s and at aphelion it's 29,300 m/s.

This page was last updated on July 18, 2015.

About the Author

Britt Scharringhausen

Britt studies the rings of Saturn. She got her PhD from Cornell in 2006 and is now a Professor at Beloit College in Wisconson.

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