These free, printable Sky Maps (star charts) by astrononer Jeff DeTray will help find your way around the night sky!
Each month, Jeff's Sky Maps highlight a wonderful event in the evening sky—including beautiful stars, constellations, planets, conjuntions with the Moon, meteor showers, and other amazing celestial objects.
Sky Map September 2014
By Jeff DeTray, Almanac astronomer writer
Visit Jeff's site at AstronomyBoy.com
This month's highlights: The Winged Horse and the Chained Princess.
When you look to the East on September evenings, it's difficult to miss The Great Square. This large asterism (unofficial star pattern) is the body of Pegasus, the Winged Horse. At the date and time of our Sky Map, The Great Square stands on one corner, looking more like a huge diamond in the sky. Pegasus is mostly upside down in this view but you should be able to follow the graceful curve of his neck, ending with the star Enid, which means “nose” in Arabic.
The Great Square stands out in part because the area inside the square is nearly empty of stars. It's a big black box bounded by four bright stars at the corners. The four bright stars at the corners of the square have Arabic names corresponding to various parts of the horse's anatomy as noted on the map. From the star Scheat (Arabic for “upper arm”) the two front legs of Pegasus extend up and to the right.
Off the nose of Pegasus is the small constellation Equuleus, the Foal or Colt. Whereas Pegasus actually resembles the outline of a horse—or, at least the front two-thirds of one—poor little Equuleus looks nothing like a horse of any kind. Nevertheless, both Pegasus and Equuleus are ancient constellations, recognized as horses since at least the 2nd century.
To the left of Pegasus lies an entire royal family consisting of Cepheus, the King of Ethiopia; Cassiopeia, his Queen; and their daughter Andromeda, the Chained Princess. In Greek mythology Andromeda was to be sacrificed by being chained to a seaside rock to prevent the wrath of the gods from destroying Ethiopia. In the nick of time Perseus, the Hero, appeared and freed the Princess Andromeda, saving her from Cetus, the Sea Monster. Perseus and Andromeda were soon wed and went on to found their own dynasty. It's a wonderful story.
This whole tale plays out in the September sky. Perseus is off to the left, racing to the rescue of Andromeda. Queen Cassiopeia appears as a big “W” shape to the upper left of Andromeda, with her husband King Cepheus above. Parts of the monster Cetus are just visible along the horizon. In between Andromeda and Cetus, and swimming in the celestial ocean are Pisces, the Fishes with its distinctive Circlet asterism.
And now for something completely different – a challenge for star gazers with exceptionally dark skies. If you can find the star Mirach, which represents Andromeda's girdle, look upward for two fainter stars, then for what appears to be a small, hazy cloud. Can you see it?
That little cloud is the Great Spiral Galaxy, the nearest large galaxy to our own Milky Way. The Great Spiral Galaxy is comprised of an estimated one TRILLION stars, but it is so far away that the combined light of all those stars look to us as a little hazy patch of sky. If you manage to glimpse the Great Spiral Galaxy in Andromeda, you will have seen the farthest object that most people will ever see with their unaided eyes. This neighboring galaxy is a whopping 2.5 million light years away. In miles, that's 14,700,000,000,000,000,000 (14.7 quintillion) miles—a long way to a “nearby” galaxy.
The Great Spiral Galaxy in Andromeda holds a special place in the history of astronomy. For hundreds of years after it was first observed with telescopes, this object was thought by astronomers to be a large collection of stars – a nebula – within our Milky Way galaxy. It was then known as the Great Nebula in Andromeda. The true nature of the nebula was then unknown.
By using very large telescopes to observe the brightness of variable stars in the “nebula,” astronomers including Edwin Hubble were able in 1925 to make the first determination of the nebula's distance from the Earth. The result was staggering. It became clear the Great Nebula was in fact not within our own Milky Way at all. It was vastly more distant than previously thought and was, in fact, another galaxy comparable to the Milky Way. At that moment, astronomers realized that many of the other “nebulas” they had observed were also galaxies. The full meaning of this discovery was profound: the Universe was many orders of magnitude larger than anyone thought.
Think of that if you're able to see the Great Spiral Galaxy in Andromeda.
Sky map produced using Chris Marriott's Skymap Pro
Click for Printable September Sky Map (PDF)
Just click, print, and bring outside!
See our Sky Watch page for more highlights of the monthly sky, courtesy of The Old Farmer's Almanac.