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Volume XVII, Issue 1 - January 1 - January 7, 2009
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Sky Watch by J. Alex Knoll

 What’s a Few Million Miles?

In earth’s distance from the sun, it doesn’t amount to much

While we’ve just begun the coldest months of the year, bask in the knowledge that the earth comes its closest to the sun — called perihelion — on Sunday, January 4. At perihelion, our planet is roughly 91 million miles from the sun, as opposed to some 95 million miles at aphelion, its farthest from the sun.

All the planets within our solar system have elliptical orbits. But whereas earth’s varies by only three degrees from perihelion to aphelion, the orbits of the nearest and farthest planets are far more eccentric, or stretched out. Mercury is 52 percent closer to the sun at at perihelion than at aphelion. And distant Pluto strays 66 percent from perihelion to aphelion.

Why, you may ask, is it cold if the earth is at its closest to the sun? While a few million miles may seem like a lot to us, it is not enough to change the weather here on earth. Our planet’s changing temperatures and its changing seasons are a result of the 231⁄2-degree axis on which earth spins. Because of that tilt, the Northern Hemisphere leans into the sun for half of the year, while the Southern Hemisphere faces the sun the other half. Just two weeks from solstice, the Southern Hemisphere is now enjoying 231⁄2 percent more daylight than we are, and as a result the temperatures there are much warmer.

Those bundled up against the cooler weather Saturday night may catch the under-rated Quadrantid meteor shower, which can deliver upward of 100 meteors an hour. Named after the long-gone constellation Quadrans Muralis, you can look between for these streaks of light to emanate between Hercules, Boötes, and Draco any time after 11pm and before dawn Sunday.


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