SKYWATCH: Perihelion: An Annual Floating ‘Holiday’
This diagram shows perihelion, when the Sun is at location 3 and the Earth is at location 2 in its orbit around the Sun (in early January). When the Earth is at location 1, in its orbit around the Sun (in early July), this is known as aphelion. This diagram is not to true scale for the Earth-Sun system; it is only to explain perihelion and aphelion. (Diagram Source: Wikipedia.org )
It’s not Earth’s distance from the sun that makes hot weather in July; it’s the tilt of its rotational axis. In summer, the North Pole tilts toward the sun, causing sunlight to arrive from more nearly overhead, spreading out less on the ground. Plus, longer days give the sun more time to heat our hemisphere.
Earth’s oblong (elliptical) orbit brings it closest to the sun around New Year’s Day, but the exact date varies from year to year. Earth was at perihelion (closest point to the sun) around 5 p.m. on Jan. 4 in 2012; in 2013 it will be around 10 p.m. (Mountain Standard Time) on New Year’s Day.
Earth will be at perihelion (closest point to the Sun) at 12:00 Midnight Eastern Standard Time on Wednesday Morning, 2013 January 2 (night of January 1-2).
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Sources: Centennial Observatory of the College of Southern Idaho, Twin Falls Times-News.
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