Jimmy Westlake: Delightful Delphinus
October 18, 2016
The autumn sky is dominated by several giant constellations that eat up a lot of territory: Hercules the Strong Man, Ophiuchus the Snake Charmer and Pegasus the Flying Horse, to name a few. Tucked in between these sky-hogs are a few tiny constellations that are a snap to locate precisely because they are so compact.
Delphinus the Dolphin is a perfect 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, just past the zenith, Deneb, a little fainter and nearly dead overhead, and Altair, high up in the southern sky. They will be high up overhead by 8 p.m.
Just east of Altair, you will find the small kite-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 flipper. It requires little imagination to picture 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 known unofficially as "Job's Coffin," suspended halfway between heaven and Earth.
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The Dolphin's two brightest stars are the ones marking the top and far right points on the diamond. The origin of their unusual names, Sualocin and Rotanev, was an unsolved celestial mystery for many years. They first appeared in a star catalogue published in the year 1814 by the Palermo Astronomical Observatory in Italy, but several decades passed before 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 pulled a fast one on the rest of us. If you reverse the letters of the two star names, Sualocin and Rotanev, they spell Nicolaus Venator.
The sneaky observatory assistant achieved immortality by naming two stars in Delphinus after himself. Every star chart in the world today includes the name of Nicolaus Venator, albeit backwards.
The star at the tip of the Dolphin's snout, 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 over 100 light years from Earth and require 32 centuries to orbit each other.
If you own a small 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 Steamboat Springs 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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