Look for the distinctive outline of Delphinus the Dolphin about halfway up in the southeastern sky at about 10 pm. This week, you can watch with binoculars as Comet Garradd glides above the stars of the Dolphin’s back.
Wednesday, August 17, 2011
Steamboat Springs The late-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 in between these sky-hogs are a few tiny constellations that are a snap to locate 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 diamond shape. To locate Delphinus, go outside at about 10 p.m. and look high in the southeastern sky, nearly overhead. There, you should spot summer’s three brightest stars marking the corners of the well-known Summer Triangle: Vega, nearly straight up; Deneb, a little fainter and to the northeast; and Altair, to the southeast of Vega. 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 a little imagination to see a dolphin here, 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 is also popularly known as Job’s Coffin, suspended halfway between heaven and Earth. The origin of this nickname is uncertain.
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 an unsolved mystery for many years. They first appeared in a star catalogue published by the Palermo Astronomical Observatory in Italy in 1814, but it was several decades later that British astronomer William Webb actually solved the riddle. It seems that an observatory assistant named Nicolaus Venator was in charge of the star catalogue project and he played a practical joke on the rest of us. If you reverse the letters of the two star names, Sualocin and Rotanev, they spell Nicolaus Venator! Thus, the sneaky observatory 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 one another. If you own a telescope, aim it at Gamma Delphini, the Dolphin’s nose, for a real celestial treat.
This week, Comet Garradd is drifting past the stars of Delphinus. Pull out your binoculars and scan just over the Dolphin’s back for an elongated fuzz ball. You can follow the little comet night by night as it glides off toward the stars of Sagitta, another tiny summer constellation.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus.