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The Sky This Week, 2013 January 29 - February 5

Counting stars and seeing shadows...
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Two views of Jupiter & three moons
Imaged 2013 January 25, 01:39 & 03:06 UT


The Moon wanes in the morning sky this week, reaching last Quarter on February 3rd at 1:56 pm Eastern Standard Time. If you find yourself up in the wee hours, look for the Moon near the bright star Spica on the morning of the morning of the 2nd. She will pass just under five degrees south of Saturn before dawn on the 3rd, then wend her way into rising stars of Scorpius to close out the week.

As the Moon heads toward the morning sky we enter another period of relative darkness for skywatchers to enjoy the evening’s stars. The year’s second "Globe At Night" observing campaign begins on the evening of the 31st and lasts until February 9th. Once again we encourage people to venture out into the night and count stars for science. Again, the technique is quite easy; simply locate the constellation of Orion and match the number of stars you see in the sky to the charts published on the Globe At Night website. Once you report your observations, the data will be used to analyze long-term changes in the amount of light pollution around the world. Last year 16,850 observations were recorded in 92 countries, and the organizers hope to surpass that number this year. The first campaign for 2013 netted over 1700 reports, so they are well on the way to their goal.

Few sights in the sky are as inspiring as the view of the winter constellations from a dark location. Once free from the orange haze of city lights the stars of Orion and his bright cohorts display their true colors against a deep blue-black background. This is a wonderful part of the sky to explore with even the slightest optical aid. Binoculars will easily reveal the Great Nebula in Orion’s "sword", the small asterism that hangs below the easternmost star in Orion’s "Belt". Just east of Orion himself is a faint band of the Milky Way that lies behind the faint stars of the obscure constellation of Monoceros, the Unicorn. Within this band your binoculars will reveal several knotty patches of light produced by star clusters and gaseous nebulae. Train a modest telescope on these patches and they will start to break up into tangled groups of faint stars. This is one of my favorite areas of the sky to explore with my small low-power telescopes. Sweeping the sky between the bright blue dazzle of Sirius and the golden glimmer of Capella offers hours of splendid viewing.

If you’re out in the early evening, keep your eyes peeled for the return of the elusive planet Mercury. The fleet planet will begin climb into the southwestern sky by the end of the week, rapidly gaining ground on ruddy Mars. The two planets are a tad more than two degrees apart at dusk on the 5th. They will close to within 3/4ths of a degree by the evening of the 7th. The best time to look for them will be about an hour after sunset, when they will be just over five degrees above the west-southwest horizon. Mercury will be the brighter of the pair as they pass through the star-poor reaches of Aquarius.

Giant Jupiter may be seen high in the east as Mars and Mercury set. The giant planet reaches the second stationary point in this year’s apparition on January 30th. Over the next couple of weeks you’ll see him gradually resume eastward motion against the background stars. Old Jove is at his best placement for observing in the early evening hours, crossing the meridian at around 8:00 pm. If you have a four-inch or larger telescope you can watch Jupiter’s innermost large moon Io cross the planet’s disc starting just before 8:00 pm EST on the 31st. At 9:10 pm the moon’s inky shadow begins to cross, then Io emerges from transit about an hour later. If you’re still up watching, the shadow leaves the disc at 11:21. As an added bonus, the Great Red Spot will be visible during the early stages of the events.

Golden Saturn still delights early risers with his warm golden glow. Although he’s making steady progress toward the evening sky, he’s still best seen in the morning sky just before the onset of twilight. He gets a nice visit from the Last Quarter Moon on the morning of the 3rd.

Finally, we can’t let the week go without mentioning one of my favorite astronomical observances, Groundhog Day. This is one of the traditional mid-season markers known as "cross-quarter" days that we still unwittingly celebrate, although most of us have no idea why. Loosely tied to a pagan festival called Imbolc, the day was brought to the U.S. by German immigrants who adopted the winter habits of the groundhog to those of their traditional old-world badger. As the mid-point of the season of winter, it does indeed mark the six-week interval leading to spring. Traditionally, if the groundhog sees his shadow, those six weeks will be cold and blustery. What will this year bring?