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The Sky This Week, 2009 September 8 - 15


The Moon wanes in the morning sky this week, working her way through the rising stars of the Great Winter Circle.  Last Quarter occurs on the 11th at 10:16 pm Eastern Daylight Time.  Look for Luna close to ruddy mars before dawn on the 13th.  On the 16th her slender crescent will be close to dazzling Venus as morning twilight begins to gather.  

 

We are entering another time of fast transition in the night sky.  As we approach the equinoxes, the rate at which the length of day changes increases to its maximum.  Old Sol now rises a minute later and sets some two minutes earlier each night this week.  Just a few short weeks ago we were enjoying light until well past 8:00 pm.  Now it’s dark at the same hour.  Although the equinox is still two weeks away, it certainly feels “fall-like” now.  The sky is also in transition.  The last stars of spring still linger after sunset, and by midnight the vast swath of “empty” sky that’s occupied by the fall constellations occupies most of the eastern heavens.  Early risers who wish to see the Moon and Venus at week’s end will find themselves greeting Orion and the stars of the winter season.  It is a great time for stargazing, especially from a dark site.  You can still find plenty of time to enjoy the summer Milky Way, which splits the sky in the later evening hours, then probe the depths of intergalactic space among the faint stars of Capricornus, Aquarius, Pisces, and Pegasus.

 

Giant Jupiter is the dominant planet in the current sky, and he’ll remain so for the rest of the year.  Old Jove glows at a bright -2 magnitude, and his cheerful warm glow adds some punch to an otherwise barren part of the sky.  He’s currently slipping slowly westward among the stars that form the “tail” of Capricornus, the Sea-Goat, and even the slightest optical aid will differentiate him from the other stars.  His four bright moons scuttle to and fro on either side of him from night to night, but occasionally several may be passing in front of his large disc or be hidden in his inky shadow, so only one might be visible.  They are an endless source of fascination for the small telescope owner.

 

Ruddy Mars gets a visit from the waning Moon on the morning of the 13th.  The red planet lies some three degrees east of Luna at that time, and appears as a wayward first-magnitude star among the “feet” of the Gemini twins.  Mars is comparable in brightness to Pollux, brighter of the Twin Stars, and sports a distinctive pink hue.  Through the telescope he’s still just a small pink dot, but his apparent diameter will more than double by the time he reaches opposition next winter.

 

The glow of Venus is easy to find in the pre-dawn sky.  By the end of the week the crescent Moon pays her a call, setting up a lovely photo opportunity on the morning of the 16th.

 

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