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The Sky This Week, 2010 October 26 - November 2

Counting stars, Ghostly ghouls, and Galilean moons
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Jupiter and Io, 2010 OCT 23, 02:07 UT
Imaged from Alexandria, VA, USA 


The Moon wanes in the morning sky this week, promising a dark and spooky evening for trick-or-treaters on Halloween. Last Quarter occurs on the 30th at 8:46 am Eastern Daylight Time. Luna spends the first few mornings of the week passing through the rising stars of the Great Winter Circle before drifting into the more sparse starfields of the springtime constellations. Look for Luna high above the bright stars of Orion on the mornings of the 27th and 28th. On the 29th she forms an elongated triangle with Gemini's Twin Stars, Castor and Pollux. Before dawn on November 1st, her waning crescent may be found six degrees south of rising Regulus in the eastern sky.

The annual Great World Wide Star Count begins on the evening of the 29th and runs its course over the next two weeks. This "citizen science" event is not only a great way to become acquainted with the evening sky and the fun of amateur skywatching, it is also a program in which everyone's observations contribute to the scientific understanding of our environment. The premise is quite simple: pick an easily recognized constellation and count the number of stars that you can see in it from night to night. If you can observe from multiple locations, then so much the better! You can report your findings on the program's website.

The Star Count is a perfect activity to engage in while going house to house on Halloween. While trailing the ghosts and goblins around the neighborhood, keep in mind that this event is rooted in very ancient traditions. The ancient Celts observed it as Samhain, the dividing time between the "lighter" and "darker" halves of the year. It is one of the astronomical "cross-quarter" days that mark the mid-points of the seasons. We still somewhat unwittingly observe these old traditions in the form of Groundhog Day, May Day, and Halloween. The fourth cross-quarter day, Lammas, falls on August 1st. Although we here in America don't observe it per se, it is often when most of us begin our summer vacations. Halloween is the darkest of these celebrations, when the line between the temporal world and the spirit world was thought to be at its thinnest. Ancestral spirits were invited into the home, while evil spirits were discouraged by participants wearing costumes and disguises.

As the Moon drifts into the morning sky, the evening hours are still dominated by the bright glimmer of Jupiter. The giant planet is easily found in the southeast shortly after sunset, and he crosses the meridian at around 10:30 pm EDT as the week begins. Old Jove is inching slowly westward against the dim autumnal constellations. The only other bright object in this part of the sky is the lonely first-magnitude star Fomalhaut, which lies almost 30 degrees to the southwest of the planet. Jupiter and his four bright moons are probably the most interesting telescopic targets in the sky after the Moon. They will be well-placed for viewing on Halloween. If you have a telescope, you might offer a peek as a "treat" for the costumed revelers haunting your neighborhood that night!

The pre-dawn sky is beginning to get interesting. The ringed planet Saturn can now be seen low in the east about an hour before dawn. The waning crescent Moon lies about 10 degrees from the planet an hour before sunrise on the 3rd. Keep an eye on this part of the sky throughout the following weeks as Venus leaps up to grab your attention.

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