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The Sky This Week, 2012 November 20 - 27

Thanksgiving cornucopia

Jupiter and its moon Io, imaged 2012 NOV 15, 03:02 UT

The Moon brightens the lengthening evening nights this week as she ascends the ecliptic. Luna waxes to Full Moon on the 28th at 9:46 am Eastern Daylight Time. November’s Full Moon is variously known as the Frosty Moon or the Beaver Moon. The latter name comes from Native American skylore reminding trappers to set their final traps for the season before the beaver ponds freeze up for the winter. The Moon spends the week drifting through the dim autumnal constellations. She won’t encounter any bright objects until she approaches Jupiter by the week’s end

Thanksgiving marks the beginning of the winter holiday season for many of us. We’re now entering the weeks when we experience the year’s earliest sunsets and nightfall seems to come well before we’re ready to end our day. It is a time of great seasonal shifts in both the climate and the sky; a time when I finally "let go" of the last of summer’s constellations even though the Summer Triangle is still prominent in the early evening. By the time the dinner hour is finished and the telescope has been set up and allowed to cool down these stars are nearing the western horizon and the rising stars of the Winter Circle are beginning to demand my attention. The flashes of color in these bright stars remind me that they will be my nighttime companions for the next several months as winter presses into spring.

The northernmost star in this large asterism now reaches prominence as the midnight hour approaches. The yellow-hued star Capella is nearing the meridian at this time, and its passage is entirely appropriate for the upcoming Thanksgiving holiday. Capella is one of the few bright stars whose name does not have Arabic origins. It derives from the Latin word for a female goat, and if you have keen eyes or a pair of binoculars you can see a small triangle of stars tucked close to the bright yellow beacon. These stars form an asterism known as "The Kids". In Roman mythology Capella represented a she-goat named Amalthea which suckled the infant Jupiter. The young god, evidently a rambunctious little boy, accidentally snapped off one of Amalthea’s horns, which became the "Cornucopia", or "Horn of Plenty". In turn the Cornucopia has become associated with our observance of Thanksgiving and the feasting that goes along with it. Amalthea has been recognized by giving her name to the fifth moon of Jupiter, discovered by the American astronomer Edward Emerson Barnard in 1892 on his first night of observing with the then-new 36-inch refracting telescope at Lick Observatory, the largest in the world at the time. This was the last moon in the solar system to be found visually. Thanks to Earth-based and spacecraft photography we now know that Jupiter has some 64 moons!

Mars still lingers in evening twilight low in the southwestern sky. This week he transits across the top of the "Teapot" asterism of Sagittarius, the Archer, passing the star at the "top" of the teapot by just one degree on the 25th. You’ll need binoculars and a low horizon to the southwest to catch this conjunction.

Giant Jupiter is now just two weeks away from opposition. He rises shortly after sunset and is well-placed for viewing by the mid-evening hours. You can’t help but notice his cheery glow in the eastern sky as he leads the bright stars of the Great Winter Circle into view. Old Jove is optimally placed for northern hemisphere skywatchers as he courses the northern reaches of the ecliptic. Jupiter is also far and away the best planet for observing with a small telescope, so if you have one get familiar with it and enjoy many hours examining the planet’s atmospheric cloud belts and bright moons.

The brilliant glow of Venus will catch your eye in the gathering twilight before dawn. If you’re up an hour before the Sun you should have no trouble spotting her in the southeastern sky, although she is dropping closer to the horizon with each passing morning. By the end of the week she catches up to baleful yellow Saturn in the faint twilight glow. She passes the ringed planet on the mornings of the 26th and 27th. On the latter date the pair are separated by less than one degree.