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Capricornus Constellation: Facts About the Sea Goat

October 2012 Sky Map of Capricornus
This sky map shows the location of the constellation Capricornus in the October evening sky as viewed from mid-northern latitudes.
Credit: Starry Night Software

Located in the Southern Hemisphere, Capricornus represents a creature that is a blend of fish and goat and the name means “goat horn” in Latin. While it is one of the Zodiac constellations identified by the Greek astronomer Ptolemy in the 2nd century, Capricornus is often used when referring to the constellationwhile Capricorn is used in conjunction with the sign of the zodiac.

Locating Capricornus

Capricornus is among the faintest constellations, just above Cancer. The 40th largest constellation, Capricornus measures 414 square degrees and contains two stars with known planets. It sits among the other constellations of the water genre, including the water-bear Aquarius, the whale-like sea monster Cetus, the fishes Pisces and Eridanus, the river.

  • Right Ascension:  21.02 hours  
  • Declination:  -20 to -23 degrees
  • Visible: between latitudes 60 degrees and -90 degrees
  • Best viewed: During the month of September at 9 p.m.

To find the arrowhead-shaped Capricornus in the sky, look for the Summer Triangle and make a line from Vega through Altair to the lower southern sky.

The tropic of Capricorn — the place where the Sun appears overhead at noon on the winter solstice — originally sliced right through its namesake constellation, but the line has since shifted to go through the constellation Sagittarius.

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Notable stars and objects

Three bright stars — alpha-2 Capricorni, beta Capricorni and omega Capricorni — form a triangle that makes it easier to pick out the constellation.

The goat’s tail is formed by delta Capricorni, the brightest star in the constellation at magnitude 2.85. It is a four-star system that is dominated by a giant white.

The second brightest star — beta Capricorni, also known as Dabih — is a multiple-star system. The two main parts to the system are beta-1 Capricorni (or Dabih Major) and beta-2 Capricorni (or Dabih Minor). Dabih Major contains an orange bright giant and a blue-white dwarf and Dabih Minor is a binary star with an A0-giant as the primary star.

Sometimes identified as the belly of the goat, omega Capricorni, is a red giant star with a highly variable luminosity and magnitude.

The star cluster Messier 30 is in the southern part of the constellation, near the barium star zeta Capricorni. M30 was part original discoveries of Charles Messier, an18th-century French astronomer.

Mythology

The constellation has its roots in the cultures of Sumeria — which identified it with a mythical figure that was half goat and half fish — and Babylonia, which portrayed it as a goat-human hybrid.

The Greeks associate the constellation with Pan, the god of nature. Part of Pan’s lore was that he helped Zeus fight the Titans to earn his spot in the heavens. He escaped the monster Typhon by jumping into Nile, but only half of his body was submerged, so he was a fish in the part of his body that remained underwater. Other spins on the tale have the constellation associated with Amalthaea, the mythical goat that acted as a foster mother to Zeus as an infant.

In astrology, which is not a science, Capricorn is the tenth sign in the Zodiac and represents those born between Dec. 22 and Jan. 19.

— Kim Ann Zimmermann, SPACE.com Contributor

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