Tuesday, December 1, 2015

The December Sky

With new month of December upon us, people in the Northern Hemisphere will be treated to the longest nights of the year as the Winter Solstice arrives on the 22nd of this month. However, when it comes to changes in days' lengths, December is pretty much a story of steady 15 hour nights, give or take a few minutes at most. So, with all of this night, what's there to see?

Cool Constellations
By nightfall in December the fall constellations are all very well-placed for early (emphasis, early!) evening viewing. First up, we will have one last chance to see the summer constellations, provided you have a good West horizon. Hurry, though, they'll quickly disappear (at least in the West) for good by month's end. Moving onto more mainstream celestial landmarks for this time of year, the Great Square of Pegasus is high overhead and the Big Dipper is scraping the Northern horizon. Starting at the Great Square, look at the double string of stars coming of third base as they constitute Andromeda. High in the Northeast is ‘W’-shaped Cassiopeia, house-like Cepheus, and a twisted ‘V’ of stars, the mythological hero Perseus. Below Perseus is the bright Capella, alpha Auriga, and below his feet, the cloudy patch that is the Pleiades. In the early evening, the South, save bright Fomalhaut, is a dark void populated by the dim constellations of Capricorn, Aquarius, Pisces, and Cetus. If you stay up a little later as in a couple of hours after dark (which is no longer a chore/something you later regret doing at this time of year), you'll see all the winter favorite like unmistakable Orion in the South, which also serves as a winter signpost to the stars. From Orion, follow a line from his belt down to blazing blue Sirius, alpha Canis Major. Following that line up will bring one to Aldebaran, alpha Taurus the bull. Imagining a line starting at bright blue Rigel (Orion's left foot) through red Betelgeuse (Orion's right shoulder) will bring you to Castor and Pollux, alpha and beta Gemini. Other winter favorites to look for include Canis Minor, Cancer, and even Leo if you wait into the night a little longer. Early birds? Well, getting up just before the Sun will bring a spring preview in the form of Virgo, Bootes, Corona, Hercules, Corvus, and even Vega just ahead of the rising Sun.

Planetary Perceptions
On the planet front, if you want to see any of our solar system neighbors, you had better be an early bird because 4 of the 5 naked eye planets make their appearances in the predawn morning sky. For starters, Jupiter and Mars both continue their climbs in the predawn Eastern sky while Venus continues dropping, which is what it began to do in October and then, noticeably in November. Also of note, the Moon will be making several near passes of these bodies in the early part of the month. As for Saturn, which disappeared into the dusk glow back in mid November, it re-emerges as a morning planet mid month and, by month's end, should be relatively easy to spot low in the predawn, Eastern sky. As for Mercury, it will become the sole evening planet when it pops out of the Sun's glare in the evening sky mid month as it heads towards greatest elongation (best visibility) around the start of the new year.


Tonight's Sky for December 1: Benjamin Wilson Born (1811)
It was on this date that Benjamin Wilson, namesake of Mt. Wilson, was born. Originally from Tennessee, Wilson traveled to California hoping to obtain passage to China but was unable to do so. Instead of traveling back home, Wilson settled in Southern California where he became a prominent politician and businessman. Wilson died in 1878 at age 66 and Mt. Wilson, Informally known as Wilson's Mountain because he owned the land on which it sat, thte name would eventually become official.

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