Jimmy Westlake: Summer’s Swan
June 15, 2008
Vega, Deneb and Altair. These are the three bright stars marking the corners of the Summer Triangle, the most prominent star pattern of summer. Although not an official constellation, the Summer Triangle is our guide to many real constellations of summer.
For example, consider the sparkling blue star that marks the northern-most corner of the Triangle, Deneb. Deneb is the brightest star in our constellation named Cygnus, the Swan, and is one of the highest wattage stars known in our corner of the galaxy. If the star Deneb replaced our sun, at the center of our solar system, Deneb would appear 80,000 times brighter than our sun does now, and we would quickly become crispy critters.
The name Deneb comes from the Arabic words for “the tail of the swan.” The star Albireo, near the center of the Summer Triangle, marks the Swan’s head. Three other stars, Gienah, Sadr and Delta, form a straight line that crosses 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 this star pattern is “The Northern Cross.” The Northern Cross, though, 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!
Aim a small telescope at Albireo, and you will see two stars of remarkably beautiful 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.
Cygnus lies smack dab in the middle of the summer Milky Way, just north of the point where it is split into two parallel bands by 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 Dumbell Nebula, near Albireo. Slowly sweeping 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 Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA’s “Astronomy Picture of the Day” Web site, Spaceweather.com, Space.com, Discover.com, MSNBC.com, NationalGeographic.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines. His “Celestial News” article appears weekly in the Steamboat Pilot & Today. His “Cosmic Moment” radio spots can be heard on local radio station KFMU. Also, check out Jimmy’s Web site at http://www.jwestlake.com.