Jimmy Westlake: Explore the Northern Cross
Vega, Deneb, and Altair — these are the three bright stars marking the corners of the Summer Triangle, the most prominent star pattern of late summer. Though, it is not one of our 88 official constellations, the Summer Triangle is a popular asterism that can serve as a guide to many real constellations of summer and fall.
Go outside about 9:30 p.m. and look straight up. There’s the Summer Triangle, right overhead. Vega is the brightest star of the trio, Altair comes in second and Deneb takes third place.
Deneb is the sparkling blue star that marks the northern-most corner of the Summer Triangle and is the brightest star in our constellation called Cygnus, the Swan. The name Deneb comes from the Arabic words for, “the tail of the swan.”
Deneb is one of the highest wattage stars in our corner of the galaxy. If it replaced our sun, at the center of our solar system, it would shine more than 100,000 times brighter than our sun does now … and Earth would become a lifeless cinder.
The star Albireo, located near the center of the Summer Triangle, marks the swan’s head and beak. Three other stars — Gienah, Sadr, and Delta — form a straight line that intersects the line connecting Deneb and Albireo and marks the swan’s outstretched wings.
Once you’ve located these five stars, you might be struck by their resemblance to a large crucifix. In fact, the popular name for Cygnus is, “The Northern Cross.”
The Northern Cross, however, is topsy-turvy from the swan, that is, Deneb marks the tail of the swan but the head of the cross and Albireo marks the head of the swan but the foot of the cross. As the swan, Cygnus seems to be gliding down the Milky Way toward Sagittarius to the south.
Aim a telescope at Albireo, and you will see two stars of beautifully contrasting colors. One is sapphire blue and the other a golden yellow.
Astronomers aren’t certain if their apparent closeness is real or merely a chance alignment. If these stars form a true binary, then they require at least 100,000 years to complete an orbit.
Cygnus sits in the middle of the bright summer Milky Way, slightly north of the point where the Milky Way star clouds split into two parallel bands due to a dark interstellar dust cloud called the Great Rift. Within her borders can be found two famous nebulae, the North American Nebula, near Deneb, and the Veil Nebula, near Gienah.
Slowly exploring this constellation with a pair of ordinary binoculars will reveal many more star clusters and nebulae hiding in the rich star clouds of the Milky Way.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Steamboat Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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