Jimmy Westlake: Catch a view of Pisces the Fish this month
November 7, 2012
The patch of the sky that appears overhead at about 8 p.m. in early November is known informally as "the celestial sea." That's because it is home to all sorts of watery constellations, including Delphinus the Dolphin, Capricornus the Sea Goat, Cetus the Whale, Eridanus the River, Aquarius the Water Carrier and Piscis Austrinus the Southern Fish. This section of the heavens earned its watery reputation because the sun makes its annual pilgrimage through this region of the sky during the months of spring, when April showers and the winter snowmelt cause the rivers to swell and overflow their banks.
Right smack dab in the middle of this celestial sea is the zodiacal constellation of Pisces the Fish. Tucked in just beneath the constellations of Pegasus and Andromeda, this pair of fish represents the mythological characters of Venus and her son Cupid. According to the legend, Venus and Cupid were strolling along the banks of the Euphrates River one day when the fire-monster Typhon appeared. Typhon was at war with the gods of Olympus and was attempting to seize control of the universe from Jupiter. To hide and escape, the gods and goddesses disguised themselves as various animals. On this occasion, Venus and Cupid transformed themselves into fish and dove into the river where the fire breathing Typhon could not follow. They tied themselves tail to tail with a ribbon so the swift currents would not separate them. Minerva later immortalized these fish in the sky as our constellation of Pisces.
While Pisces has no bright, flashy stars, it is nonetheless easy to spot because of its distinctive pattern. Just south of the Great Square of Pegasus you'll find a small oval formed by seven stars, nicknamed "The Circlet." This pattern represents Venus in the form of a fish. A faint string of stars representing a ribbon trails off behind the Circlet toward the east to Pisces' alpha star, named Alrischa, meaning "the knot." Another stream of faint stars extends northward from Alrischa to a triangle of stars on the eastern side of the Great Square and represents Cupid. Pisces is a very large constellation, ranking 14th out of the 88 official constellations.
Pisces occupies an important crossroad of the sky. This is where the equator of the sky and the annual path of the sun cross each other on the first day of spring each year. The moment the sun reaches this point, called the vernal equinox, spring begins in the Northern Hemisphere. In 2013, this will happen at 5:02 a.m. March 20. Of course, when this occurs, the stars of Pisces will be hidden behind the sun in our daytime sky, so step outside this month to catch a glimpse of this delightful fishy constellation.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. Check out Westlake's astrophotography website at http://www.jwestlake.com.