What is Perihelion?

January 2, 2010 0 Comments

As the Earth orbits the Sun, it follows an elliptical path rather than a circular one.  Also, the Sun isn’t exactly in the middle of the Earth’s orbit…rather, it is off to one side just a bit.  As a result, the distance from the Earth to the Sun changes during the course of the year.  It turns out that in early January our planet is over 3 million miles CLOSER to the Sun than we are in July.  This point on the Earth’s orbit is called Perihelion…and we reach it about January 3-4 each year.  You might not be able to tell with the naked eye, but the Sun’s disk is slightly larger in the sky right now…

A comparison between the Sun's disk at Aphelion and Perihelion

A comparison between the Sun

A nice diagram from NWS/North Platte

A nice diagram from NWS/North Platte

Another good diagram from U of Oregon Physics Department

Another good diagram from U of Oregon Physics Department

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