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The Sky This Week, 2009 November 17 - 24

Meandering Through the Galaxy...

The Moon wends her way back into the evening sky this week, waxing from a thin crescent in the southwestern sky to First Quarter on the meridian by week’s end.  First Quarter occurs on the 24th at 4:39 pm Eastern Standard Time.  Luna passes three degrees north of bright Jupiter on the evening of the 23rd.  Otherwise she spends most of the week drifting through the faint stars of autumn’s dim constellations

Before Luna completely washes out the early evening sky you have one last chance to say goodbye to the bright stars of the Summer Triangle as twilight settles into full darkness.  Vega, Deneb, and Altair hang high in the western sky after dusk, and folks in darker locations can still see some of the best star-clouds of the Milky Way passing through the Triangle’s heart.  Follow the soft band of light over to the northeast and you’ll start to see some of the rising bright stars of winter.  The Milky Way is less dense in this direction because we are looking away from the galactic center toward the edge of the galaxy’s disc that’s closest to our solar system.  Notice how the brighter stars tend to congregate along the Milky Way’s path.  Now look toward the south, away from the galactic plane.  There are very few bright stars in this direction since our line of sight is almost parallel to the galaxy’s south pole.  This should provide a clue about our place in the grand scale of the cosmos; we inhabit the surface of a small planet orbiting a very ordinary star that lies toward one edge of a huge flattened disc of hundreds of billions of other stars which is itself but one of billions of other external galaxies.  The nearest of these, Messier 31 in the constellation of Andromeda, can be seen without optical aid from dark locations, and binoculars will reveal it to suburban skywatchers who know where to locate it.  However, “nearest” is a relative term.  At the speed of light, photons from the Great Andromeda galaxy take some 2.5 million years to reach us!

Photons from giant Jupiter have a much less arduous trip.  They only take about 42 minutes to reach us.  Old Jove crosses the meridian during the evening twilight hours, but he’s still high enough to get a few hours of telescopic observation in before he begins to wallow in horizon haze and turbulence.  Time is running out on the giant planet, though, as he now sets about three minutes earlier each night.  In another month you’ll be hard-pressed to see him through still air.

As Jupiter sets in the southwest, ruddy Mars begins to climb in the east.  If you’ve been watching the red planet over the past few months you’ve probably noticed his near break-neck pace through the stars of Aries, Taurus, and Gemini.  Now he’s beginning to slow his gait as he drifts slowly eastward between Cancer and Leo over the next few weeks.  He will cover just a few degrees of sky before he reaches the first stationary point of the upcoming opposition around the time of the winter solstice.  Modest telescopes can now begin to pick out detail on his slowly growing apparent disc.

Golden Saturn is still best seen in the pre-dawn hours.  The ringed planet now rises at around 2:00 am, so by the first hint of dawn he’s well-placed for viewing in the southeastern sky.  The north face of the ring system is now enjoying sunlight for the first time in 15 years!