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The Sky This Week, 2016 August 2 - 9

More Milky Way Meanderings
The Summer Triangle Milky Way and the "Great Rift"
imaged 2013 August 12 from Fishers Island, NY

The Moon returns to the evening sky this week, waxing through her crescent phases as she moves along the ecliptic’s southern reaches. Try to locate her shortly after sunset on the evening of the 4th; the fleet planet Mercury will be within a degree to her west, and the brighter glow of Venus will be about 10 degrees farther west, just above the horizon at 9:00 pm Eastern Daylight Time. On the evening of the 5th Luna will be just over a degree from Jupiter in the gathering evening twilight. First Quarter occurs on the 10th at 2:21 pm EDT.

During the early part of the week you can still get a nice view of the summer Milky Way once evening twilight ends. We discussed the galactic center last week, so this time let’s look a bit farther north at the bright band that pierces the Summer Triangle marked by the stars Vega, Deneb, and Altair. By 10:30 pm the sky should be fully dark, and the Triangle will be nice and high in the east. From a dark location this is one of the most spectacular parts of the Milky Way as it is here that the luminous band appears to be split by a dark rift that continues down toward the southern horizon. If you look at this rift with binoculars or a telescope you’ll soon discover that there are many fewer stars in the rift. This is due to vast clouds of opaque gas and dust that define the plane of the Galaxy. Long-exposure images will show many discrete dark clouds. Fromm extremely dark locations many of these can just be glimpsed with the naked eye. In fact, many ancient Mesoamerican cultures identified these dark patches as their version of "constellations". Unfortunately there aren’t that many locations left in the U.S. where we can enjoy such pristine skies, but the bright parts of the Milky Way are still a wonderful hunting ground for other sights such as star clusters and bright nebulae. The constellation of Cygnus, the Swan, dominates the visible stars within the Summer Triangle. The bright star Deneb marks the Swan’s tail, and the third-magnitude star Albireo, located almost squarely in the Triangle’s center, marks its head. It doesn’t take too much imagination to draw out a stick-figure swan flying toward the south along the Milky Way. One of my favorite depictions of this constellation comes from Inuit skylore; they see a man paddling a kayak along the "Pebbly River". For a nice easy telescopic treat, look at the star Albireo. It resolves in almost any telescope into a beautiful double star with blue and gold colors.

You can still see all five of the naked-eye planets this week. The best time to do so would be the evening of the 4th. As mentioned earlier the Moon is quite close to Mercury then, and since the fleet planet is probably the most difficult to spot this will be your best chance to see him.

You should start looking for Venus just after sunset in the western sky. Use binoculars to find her bright glow about six degrees above the horizon 15 minutes after sunset.

Jupiter gets a visit from a slender crescent Moon on the evening of the 5th. He is now only visible during the waning evening twilight, losing a little more ground to the advancing Sun each evening. He’ll be gone from the sky in another few weeks.

Mars continues to move eastward through the stars that for the "head" of Scorpius. Watch him close in on the star Dschubba, the middle star of the three that form the head. By the week’s end the red planet will pass just under a degree south of the star and set his sights on Saturn.

Saturn crosses the meridian just before 9:00 pm, so you have plenty of time to enjoy viewing him above the stars of Scorpius. He stands about six degrees north of the Scorpion’s brightest star Antares and forms an ever-changing triangle with the star and Mars during the course of the week. This triangle will continue to flatten over the next several weeks. This will turn into a line around August 23rd.

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