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The Sky This Week, 2012 January 24 - 31

Tantalizing treats to tempt the telescope

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The "Sword" of Orion, 2012 JAN 8,
imaged from Alexandria, VA


The Moon waxes through her crescent phases in the early evening sky this week, climbing rapidly from the western horizon with each passing night. First Quarter occurs on the 30th at 11:10 pm Eastern Standard Time. Look for Luna in the company of bright Venus on the evenings of the 25th and 26th. On the 29th and 30th she will share the limelight with Jupiter before moving toward the stars of the Great Winter Circle.

This is a great week to set up the telescope in the early evening. The waxing crescent Moon provides a new set of interesting landscapes to explore with each passing night. Scores of craters large and small, huge escarpments that run hundreds of miles in length, and vast lava fields dominate the early stages of each lunation. Several of the Moon’s most fascinating formations can be seen under the low Sun angle of the lunar terminator during these nights, and if you tire of exploring them you still have Venus and Jupiter to look at! If a telescope found its way into your home over the holidays, now is a terrific time to give it a good "shakedown cruise"!

By late evening Luna is gone from the sky and you have a chance to continue your explorations among the bright stars of the Great Winter Circle. The stars of Orion in particular offer a great variety of intensity and color that are best brought out in a low-power view through a small telescope. One object in particular is well worth seeking out, the so-called "Great Nebula" in Orion’s "sword". The sword asterism is easily located just below the left-most star in the Hunter’s "belt". Binoculars and small telescopes reveal dozens of gleaming blue stars here in three distinct clumps, with the middle one showing a distinct fuzzy appearance. Use higher power to zoom in on this luminous patch; you’ll see a knot of several stars surrounded by softly glowing nebulosity. Even from severely light-polluted skies this object stands out, and the more aperture you use on it the more detail is revealed. The central region in particular is a maze of fine structure, once described by the 19th Century astronomer Sir John Herschel as resembling "the breaking-up of a mackerel sky". The nebula glows from the light given off by fluorescent gas, mostly neutral hydrogen and doubly-ionized oxygen, and most of the stars in the vicinity were born in the vast cloud. From very dark sites the gas clouds associated with it permeate most of the background of the constellation!

Bright Venus is worth a passing look through the telescope, which will reveal her to be shaped like a waxing gibbous Moon. Over the course of the next several months this phase will gradually decrease, so give her a glimpse once a week or so to follow this progress. You’ll have no trouble finding her in the early evening sky even after the Moon leaves her behind.

Jupiter is also easy to spot, both before and after he plays host to the Moon on the 29th and 30th. Unlike Venus, Old Jove barely shows any phase effect, but this is more than made up for by his much larger apparent disc and the wealth of detail on his cloud-shrouded surface. Jupiter also has something else that Venus doesn’t: moons. His four largest satellites, discovered over 400 years ago by Galileo, provide an endless variety of configurations.

Ruddy Mars now rises at around 9:00 pm EST, and by midnight he should be high enough for a glimpse through the telescope. The red planet’s disc is still quite small when compared to Jupiter’s, but modest instruments should be able to glean some detail on his rusty face. Mars is still a few weeks away from opposition, but if you want to start observing him regularly now’s the time to start.

Finally, golden Saturn breaks into the evening sky by the week’s end, rising just before midnight. The best time to observe the ringed planet is still just before dawn when he’s near the meridian. He will spend this apparition fairly close to the blue-tinted star Spica, so he will also be easy to recognize when his time in the spotlight comes later this spring.

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