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Astronomy From Your Back Yard - 12/01 to 12/07 2010

By Dave Grosvold

  
     
  
On Friday morning, about 1/2 hour before dawn, look for a razor-thin crescent Moon far below Venus in the southeastern sky. Venus is at its maximum brightness magnitude 4.9, and as is commonly known as the “Morning Star”. Far above Venus is Spica in Virgo, and above that, Saturn at magnitude +0.9. Saturn's rings are 9° or 10° from edge-on now, and early dawn is the best time to observe the ringed planet all this week.

  
Early in the evening all week, the constellation Cassiopeia floats very nearly directly overhead when you face north. Look for an M-shaped grouping of stars high above you for Cassiopeia. About halfway from Cassiopeia to the horizon lies Polaris, the North Star. Polaris is the brightest star in the otherwise dim constellation of Ursa Minor, commonly known as the Little Dipper.

Far below Polaris, and very nearly below the horizon, lie the upper-most stars of the Big Dipper asterism, part of the constellation of Ursa Major. The tail of Draco wends its way between Polaris and the stars of Ursa Major. This far south, you may not even be able to spot the stars of Ursa Major without finding a nearly flat horizon clear of obstructions.

Jupiter shines high in the south to southwest during evening, the brightest star-like point in the evening sky. Jupiter's missing South Equatorial Belt is finally starting to re-group, becoming barely visible as dark material spreads from a series of telltale bright storm spots that appeared three weeks ago.

On Friday evening, Jupiter's moon Europa reappears from eclipse out of Jupiter's shadow around 7:30 PM CST. Watch and wait for a few minutes, and a small telescope will show it gradually become visible just east of the planet.

  
Later in the evening, look to the east to see the starry harbingers of Winter, orange Aldebaran in Taurus, fiery red Betelgeuse and blue-white Rigel in Orion, bright yellow Capella in Auriga, the TwinsCastor and Pollux in Gemini, brilliant blue-white Sirius, the brightest star in the sky — and the brightest in Canis Major. Don't forget the white binary star system Procyon in Canis Minor, considered the seventh brightest in the sky. Betelgeuse, Sirius, and Procyon make the three vertices of the Winter Triangle asterism.

Mercury, at magnitude 0.4 is now at the best time for observing its current evening apparition. Still, it's quite low on the horizon, and a challenge. Look for it in mid-twilight just above the southwest horizon.

New Moon occurs on Sunday, December 5th at 11:36 AM CST, so both Saturday evening and Sunday evening will be good times to observe deep-sky objects (those outside our Solar System.)

This week is a great time to see Iridium Flares, both in the morning and evening. At 6:02 PM CST on Sunday, December 5th, Iridium 63 flares to magnitude -0 low in the western sky at an altitude of 11°. Just a few minutes later at 6:37 PM CST, Iridium 49 flares to magnitude -2 at an altitude of 30° in the south. Early Monday morning, at 7:01 AM CST, Iridium 46 flares to an absolutely brilliant -8 magnitude high up in the sky at 71° altitude. Look for it at azimuth 339° (in the NNW.) This is the brightest flare that will occur over the coming week.

Monday evening, Iridium 65 and 66 put on a show at 5:47 PM and 5:56 PM CST, respectively. Iridium 65 will flare to magnitude -1 and Iridium 66 will reach magnitude -2. Both satellites will be low (at altitudes of 13° and 10°) in the Western sky. On Tuesday morning at 6:55 AM CST, we see Iridium 46 reach a fairly bright magnitude -5, pretty high up at an altitude of 69° in the NNW, and then Tuesday evening at 5:41 PM CST, Iridium 68 also flares to magnitude -5 low at an altitude of 14° in the Western sky. You can find out more about these at the Heavens Above web site.
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