CAPRICORNUS The "The Sea Goat" pronounced KAP-rih-KOR-nus

Chart showing the constellations.

Capricornus is depicted as a goat with a fish tail. Amphibious creatures feature prominently in ancient legends, and the origin of Capricornus dates back to ancient times. Ptolemy assigned twenty-eight stars to this group which is not conspicuous but easily recognised by the two stars α and β Cap, following Sagittarius, the former being a pair to the unaided eye.

About 2,500 years ago the Sun used to reach its farthest point south of the equator in Capricornus on the winter solstice, December 22nd (northern hemisphere). The latitude on Earth, 23.5° south, at which the Sun appears overhead at noon on the winter solstice, therefore became known as the Tropic of Capricorn. Because of precession, the (northern) winter solstice has now moved into the neighbouring constellation of Sagittarius, but the Tropic of Capricorn retains its name.

To find Capricornus, look north in the late evening, over halfway up the sky to find alpha and beta Cap about halfway between the bright stars Fomalhaut and Altair.

Chart showing the Constellation.

Capricornus. 7.1 kb

Constellation Sagittarius Constellation Microscopium Constellation Grus Piscis Austrinus Constellation Aquarius Delphinus & Equuleus Constellation Aquila

Some stars and interesting objects in the Constellation

α Capricorni (Algedi or Giedi, meaning goat or ibex) is a multiple star, consisting of two unrelated yellow and orange stars 1600 and 120 light years away, of magnitudes 4.2 and 3.6 respectively, seen separately with the unaided eye or binoculars. Larger telescopes reveal that each star is itself double.

α1 Cap, the fainter of the pair, has a wide 9th magnitude unrelated companion, visible in small telescopes. α2 Cap is a genuine binary star, with an 11th magnitude companion. Telescopes of greater than 100 mm aperture show that this faint companion is itself composed of two close 11th magnitude stars.

β Cap (Dabih, meaning 'lucky one of the slaughterers') is a magnitude 3.1 golden yellow star 250 light years away. It has a wide blue magnitude 6 companion, visible in binoculars or small telescopes. The brightest star is really five connected stars, shown by a mixture of spectroscopic and occultation techniques.

γ Cap (Nashira, the fortunate one) is a magnitude 3.7 white star 100 light years distant.

δ Cap (Deneb Algiedi, goat's tail) at magnitude 2.9 is the brightest star in the constellation. It is an eclipsing binary star, varying by a barely perceptible 0.2 magnitude every 24½ hours. It lies 49 light years away.

π Cap is a magnitude 5.3 blue-white star, with a close magnitude 8.5 companion 470 light years away, visible in small telescopes as a fine pair in a field of widely scattered stars..

M 30 (NGC 7099) is a beautiful 8th magnitude globular cluster 40,000 light years away, visible in small telescopes. The well-resolved centre is compressed and two short straight rays of stars emerge north-west, while from the northern edge irregular streams of stars come out almost spirally eastwards.

Visibility

Capricornus will be to the north, high in the sky late evening at the beginning of September and at mid evening by the end of the month. It will remain visible in the evening sky through October and November, but by the end of the latter month will be getting rather low to the west as the sky darkens after sunset.

Since the constellation is some way south of the equator it is above the horizon as seen from New Zealand for about fourteen and a half hours.