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The Sky This Week, 2014 July 15 - 22

Under a river of stars...
M20_140705_04small.jpg
Messier 20, the "Trifid Nebula" in Sagittarius
Imaged 2014 July 5 from near Morattico, Virginia
80mm f/6 Antares Sentinel refractor with Canon EOS Rebel T2i DSLR

The Moon wanes in the early morning sky this week, reaching Last Quarter on the 18th at 10:08 pm Eastern Daylight Time.  Luna wends her way through the sparse starfields of the autumnal constellations before encountering the first stars of winter by week’s end.  Look for Luna just over a degree northwest of the bright star Aldebaran before dawn on the 22nd.

As the Moon slips into the morning sky the evening hours are once again graced by darkness, allowing us to view the splendor of the brightest parts of our home galaxy, the Milky Way.  One of the highlights of summer for me is to travel to locations far from city lights, preferably near the water, and just sit back in a lawn chair to watch the ghostly glow of diffuse light slowly wheel overhead as the night passes.  There are many subtle features that can be seen with the unaided eye.  Perhaps the most fascinating of these are the dark “rifts” that intersperse the brighter star clouds, especially in the areas of the constellations of Cygnus, Aquila, Ophiuchus, and Sagittarius.  These dark areas are vast clouds of cold gas and dust that mark the plane of the galaxy’s disc, and it is in these regions that the raw ingredients for the formation of stars and planets may be found.  These rifts continue well below the southern horizon where they were noted by many pre-Columbian cultures, and especially the Inca.  To these ancient inhabitants of the spine of the Andes the dark shapes in the sky were their equivalent of our constellations, and much of their sky lore is made up on these patterns of darkness.  The American astronomer Edward Emerson Barnard pioneered the photographic cataloging of the Milky Way’s dark regions, eventually compiling a catalog of 370 discrete dark areas.  You can spot many of these dark areas with a pair of binoculars as you peruse the Milky Way on a clear July night.  You can also spot dozens of bright knots of stars and wispy patches of gaseous nebulae with this simple optical aid.  My favorite telescope for viewing the Milky Way is a small 80mm (3.1-inch) refractor with a wide-field eyepiece.  This breaks up many of the galaxy’s brighter areas into clouds of innumerable stars crisscrossed by some of Barnard’s “dark nebulae” as well as the brighter star clusters and glowing gas clouds recorded by the French astronomer Charles Messier.  This, to me, is a perfect summer night!

In the evening sky we still have some planets to view, but our time with them is growing shorter with each passing week.  Ruddy Mars is now on the run from the advancing Sun, and you can watch his nightly progress as he drifts eastward from the bright blue star Spica.  The red planet is now well over a full magnitude fainter than he was at opposition back in April and his telescopic disc is now just over half his apparent opposition diameter.  Mars will continue to gather speed against the stars over the next few weeks, so he will remain a fixture, albeit a fading one, in the southwestern sky for the rest of the year.

Saturn reaches the second stationary point in this year’s apparition on the 21st.  It will be hard to notice his resumption of direct eastward motion for several more weeks, though, since he takes nearly 30 years to make one complete circuit of the sky.  He is well-placed for viewing through the telescope from about an hour after sunset until around midnight, and it’s well worth the time to give him a look.  We are now seeing the ringed planet close to his maximum phase angle, which means that the planet’s disc now casts its longest shadow on the rings for a pleasing, near-“3D” effect.

If you’re up before the Sun at around 5:00 am you should have no trouble spotting Venus low in the southeastern sky each morning.  You may also notice a couple of bright stars forming a large triangle with the planet.  These stars are Capella and Aldebaran, and they help to remind us that the seasons inexorably change.  By the time these stars are prominent in the evening sky the memories of hot July nights under the Milky Way will be a distant memory.


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