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The Sky This Week, 2016 September 27 - October 4

Sights in the celestial Swan
Messier 27, the "Dumbbell Nebula" in Vulpecula
imaged 2016 August 23 from Fishers Island, NY

The Moon returns to the evening sky by the end of the week, with New Moon falling on September 30th at 8:11 pm Eastern Daylight Time. Luna presents a slender crescent in the early morning sky before New Moon, then gradually climbs into the evening twilight after. If you’re up at 6:30 am on the morning of the 29th, look for a sliver of a lunar crescent just one degree below the glimmer of Mercury in the brightening morning twilight. You should have a much easier time spotting the waxing crescent Moon above the bright planet Venus in the evening twilight of October 3rd.

Now that the hazy skies of summer seem to be behind us we have several moonless nights to do some citizen science by counting stars for the Globe at Night program. This month’s featured constellation is Cygnus, the Swan, easily found as one of the star patterns incorporated into the Summer Triangle asterism. The Swan’s brightest star is Deneb, which is the faintest of the three bright Triangle stars. The rest of Cygnus resembles a large cross which can be easily traced out in most suburban skies. Using the finder charts on the Globe at Night website, you can estimate the brightness of the faintest stars you can see from your observing site to help map the distribution of light pollution around the world.

Once you’ve done counting stars in Cygnus, take a look at some of the more interesting features of this fine constellation. From a dark location it is embedded in some of the brightest star clouds of the Milky Way, and it is where the "Great Rift" in the Galaxy seems to begin. One of the constellation’s best treats for any sky is the star Albireo, which marks the Swan’s "head". Viewing this star with any telescope reveals it to be a fine double star with a wonderful color contrast consisting of a bright yellow star and a fainter blue companion. I like to refer to this pair as the "Navy Double" because of this color contrast, which to me shows up best in small instruments. For dark-sky observers, there are two small constellations just southeast of Albireo which contain some interesting deep-sky objects. Both objects are visible in binoculars but are best seen in modest telescopes. You’ll find Messier 71, a compressed cluster of faint stars, in the constellation of Sagitta, the Arrow, a small line of stars about 10 degrees from Albireo. In small telescopes it is a fuzzy patch of light, but larger instruments resolve its true nature. Five degrees northeast from M71 is an "M"-shaped asterism that forms part of Vulpecula, the Fox. Just south of the center of the "M" is another fuzzy patch known as Messier 27. This object won’t resolve in any telescope since it is an expanding cloud of luminous gas surrounding a dying star. It is popularly known as the "Dumbbell Nebula" due to its resemblance to an exercise weight. There are many other interesting things to spot in this wonderful patch of the sky, so spend some time examining it.

You should now have no trouble spotting the bright planet Venus in the evening twilight sky. She pops into view shortly after sunset in the southwest and remains visible until she sets at around 8:00 pm.

Saturn continues to plod eastward above the bright stars of the constellation Scorpius. Look for him above the bright star Antares. You can still get a pretty decent view of him in the telescope during twilight and the early evening.

Mars slides eastward against the stars of Sagittarius. He begins the week above the "spout" of the "Teapot" asterism. By the end of the week he closes in on the star Kaus Borealis, which marks the teapot’s "top".

Early risers have a chance to see Mercury in morning twilight. The fleet planet reaches his greatest elongation west of the Sun on the morning of the 28th. He will remain visible for the next week or so among the rising stars of Leo, the Lion.

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