Jimmy Westlake: Summertime’s delightful dolphin
July 30, 2013
The summer sky is dominated by several giant constellations that eat up a lot of territory: Hercules the Strong Man, Ophiuchus the Serpent Bearer and Ursa Major the Great Bear, to name a few. Tucked between these sky hogs are a few tiny constellations that are a snap to locate precisely because they are so small.
Delphinus the Dolphin is a great example. Even though Delphinus contains no star brighter than third magnitude, one's eye is immediately drawn to its small, distinctive shape.
To locate Delphinus, start by first finding the three bright stars of the Summer Triangle: Vega, nearly straight up, Deneb, a little fainter and to the northeast, and Altair, to the southeast of Vega. They will be high in the eastern sky by 10 p.m. Just east of Altair, you will find the small diamond-shaped pattern of Delphinus the Dolphin. The four main stars form the head and body of the dolphin and a fifth star, off to the lower right, marks his tail. It requires little imagination to see a dolphin jumping up out of the celestial sea. You can just about cover the entire constellation of Delphinus with your thumb held at arm's length. The diamond-shaped asterism of Delphinus also is popularly known as Job's Coffin, supposedly suspended halfway between heaven and Earth.
The Dolphin's two brightest stars are the ones marking the top and right points on the diamond. The origin of their unusual names, Sualocin and Rotanev, was a mystery for many years. They first appeared in a star catalog published in 1814 by the Palermo Astronomical Observatory in Italy, but several decades passed before British astronomer William Webb solved the riddle. It seems that an observatory assistant named Nicolaus Venator was in charge of the star catalog project, and he played a practical joke on the rest of us. If you reverse the letters of the two star names, they spell Nicolaus Venator. Thus, the sneaky assistant achieved immortality by naming two stars in Delphinus after himself.
The star at the tip of the Dolphin's nose, named Gamma Delphini, is resolved with any small telescope into one of the most beautiful binary stars in the heavens. Gamma's two colorful stars are just more than 100 light years from Earth and require 32 centuries to orbit each other. If you own a telescope, aim it at Gamma Delphini, the Dolphin's nose, for a real celestial treat.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His Celestial News column appears weekly in the Steamboat Today. Check out his astrophotography website at http://www.jwestlake.com.