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The Sky This Week, 2011 February 1 - 8

Will he or won't he?


The Asaph Hall Building, U.S. Naval Observatory 

The Moon returns to the evening sky by the week’s end. New Moon occurs on the 2nd at 9:31 pm Eastern Standard Time. Look for Luna near bright Jupiter in the western sky on the evenings of the 6th and 7th. On the evening of the 3rd you’ll have the rare opportunity to sight a very young crescent Moon. If you look about five degrees above the west-southwest horizon at around 6:00 pm EST you may be able to spot the 21-hour-old crescent as a thin, hair-like gash of light against the twilight sky. A very clear atmosphere and an unobstructed view of the horizon are essential to accomplish this feat, and a pair of binoculars will make it a little easier.

February 2nd is one of our more popular "semi-holidays", Groundhog Day. It is similar in character to Halloween in that most everybody is aware of it and "observes" it in some fashion, but they’re not really sure why they do. We’re all familiar with the annual ritual of a group of nattily-dressed gentlemen in top hats and tails gathered on a small hilltop in rural Pennsylvania to await the outcome of a certain large indigenous rodent’s ability to "see his shadow" and therefore predict the coming of spring. Once a year atop Gobbler’s Knob in Punxsutawney, PA the eyes of the world settle on Phil the Groundhog as dawn breaks. If Phil casts a shadow, then there will be six more weeks of winter, and if he doesn’t, well, there will still be six more weeks of winter! Groundhog day falls mid-way between the winter solstice and the Vernal equinox, and since the average season is 12 weeks long the answer either way is a sure bet. Despite the modern exploitation, the roots of Groundhog Day date back well over a thousand years to an early Christian feast known as Candlemas. This was one of the so-called "cross-quarter" days of ancient timekeeping tradition, which, along with the quarterly seasonal markers, were the dates when serfs paid rent to their feudal lords. Halloween is the other cross-quarter day that’s still widely observed here in America, and Europeans still observe May Day. Lammas, the final cross-quarter day, falls on August 1st, which is the traditional start of summer vacation days in many parts of the world.

Bright Jupiter is making haste toward the western horizon in the early evening hours. He is now best glimpsed through the telescope about half an hour after sunset. At this time the background sky should be dark enough to offer enough contrast to see his moons and pick out some surface details. As the night darkens the giant planet’s light begins to fade due to atmospheric extinction, and you’ll be looking for fine detail through more of our turbulent atmosphere. He sets before 9:30 pm.

An hour after Jupiter departs, golden Saturn begins to lift into the eastern sky. The ringed planet should be high enough for a telescopic glimpse by midnight, and if you’re a real night-owl he’ll keep you company until dawn. He will be the next telescopic highlight as he approaches opposition in the early spring.

Venus scurries along the southern reaches of the Ecliptic this week, passing through the stars of Sagittarius, the Archer. She spends most of the month at her most southerly declination, and for most of the rest of spring and summer she will skirt the horizon in twilight. This will be the last month to enjoy her in the relative darkness of the pre-dawn sky.