The Sky This Week, September 8 – 15, 2015 !

The Sky This Week, 2015 September 8 – 15

Count stars in the evening, take pictures in the morning.
Messier 31, the Great Andromeda Galaxy
Imaged 2015 August 8 with a Canon EOS Rebel T2i DSLR, 80mm f/6 Antares Sentinel refractor,
20 90-second subframes @ ISO 3200 at Fishers Island, New York

The Moon graces the pre-dawn sky early in the week, then disappears in the glare of morning twilight before New Moon, which occurs on the 13th at 2:41 am Eastern Daylight Time. This particular New Moon will produce a partial solar eclipse that won’t be visible to us here in the US. If you’d still like to travel to see it, you’ll need to book passage to southern Africa, the Kerguelen Island archipelago in the southwestern Indian Ocean, or Antarctica. Maximum eclipse will be best seen from the latter, where penguins and a few research scientists will see some 70% of the Moon’s disc obscured by the Sun. This will lead up to a spectacular total lunar eclipse that will be visible from our part of the world on the night of September 27-28. You’ll have a wonderful photo opportunity before dawn on the 10th, when the waning crescent Moon passes just three degrees from dazzling Venus, which has vaulted into the morning sky after last month’s conjunction with the Sun. On the following morning, see if you can spot the bright star Regulus just to the north of the very slender lunar crescent. If it’s really clear you may also spy the ruddy glow of Mars just 8 degrees above Luna and the star.

A waning crescent in the morning sky means that it’s “dark sky” time for all of us. If you’re living in a place with no streetlights or urban areas nearby you’ll have a ringside seat to the summer Milky Way, which seems to bisect the sky by the end of evening twilight. Even if you live in a city you can still find the summer’s brighter stars, and by doing so you can help astronomers study the effects of light pollution around the world. The citizen-science Globe at Night program encourages skywatchers everywhere to count the number of stars they see in particular areas of the sky as the seasons progress. For September your target constellation is Cygnus, the Swan, whose brightest star Deneb is the faintest of the three bright stars that make up the Summer Triangle asterism. This distinctive feature is now directly overhead between 9:00 and 10:00 pm. From the Globe at Night website select the link to Cygnus and compare your view with the star maps that depict different limiting magnitudes. From my home in the suburbs I’m lucky to see third-magnitude stars, but on my recent visit to Belle Isle State Park in Virginia’s Northern Neck stars of sixth-magnitude were visible. How many can you see from your favorite observing site?

As the night progresses another geometric figure rises in the eastern sky. The asterism known as the “Great Square” looks like a giant diamond suspended over the eastern horizon as twilight ends, and by midnight it’s nearing the meridian high in the south. The Square is a part of the larger constellation of Pegasus, the winged horse which carried the hero Perseus to rescue Andromeda in a famous legend from mythology. Andromeda herself can be traced out as two diverging chains of stars, one relatively bright, the other rather faint, which seem to join at the upper left-hand corner of the Square at the star Alpheratz. If you’re in a dark location, follow the brighter chain of stars to its second member, then scan northward past two fainter stars. On a good night you should see a smallish smudge of diffuse light that resembles a detached bit of the Milky Way. This is actually the famous Andromeda Galaxy, our closest large galactic neighbor some 2.5 million light-years distant. Binoculars begin to show its true nature, and in a medium-sized telescope the eyepiece is filled with a diaphanous glow that defies resolution. It is the most distant object we can see with our unaided eyes!

Saturn still lingers in the southwestern sky as evening twilight deepens. The ringed planet is gradually moving eastward toward the stars that form the “head” of Scorpius, and you still have an hour or so once he becomes visible to get a decent view of him through a telescope. His eastward plod is very slow, however, and he is gradually losing the battle with the approaching Sun.

All of the other planets are congregating in the morning sky. By mid-October Mercury, Venus, Mars, and Jupiter will all appear before the rising Sun. Stay tuned…


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