ANDROMEDA, LADY OF FALL by Brian Mason One of the most prominent constellations that can be seen in the autumn season of the Northern Hemisphere is the chained lady of the sky, Andromeda. In Greek mythology, Andromeda was the daughter of Cepheus and Cassiopeia, the King and Queen of Ethiopia. Andromeda was punished due to the boasting of her mother, Cassiopeia. In some traditions, Cassiopeia was boasting of her own beauty, while in others she spoke of the beauty of her daughter, Andromeda. She was compared in beauty to the Nereids, the water nymphs, who complained to their father, Poseidon. Poseidon sent the sea creature Cetus to destroy Ethiopia for this insult. The only way King Cepheus could avoid this horror was to sacrifice his daughter to Cetus. Cepheus had Andromeda chained to a rock by the sea to await her fate. The fates had other intentions, though: The hero Perseus came upon the scene and, after warning Andromeda to keep her eyes tightly shut, exposed Cetus to the severed head of Medusa. This gruesome creature's gaze, even in death, would turn any living thing it met eyes with into stone. Cetus saw Medusa's head and was transformed into solid rock. Perseus then freed Andromeda from her bonds and the two were later married. While the Greek myth is certainly ancient, the story itself probably originated even earlier in the region of Mesopotamia (now modern Iraq) in the Babylonian "Epic of Creation". Elements of the Greek myth tie in with the Babylonian story of the hero Bel Marduk and the evil dragon Tiamat. The Western constellation of Andromeda also shares its stars with the more complex Chinese constellations Koui-siou (the House of the Sandal), Kiun-nan-mun (the Southern Camp Gate), and T'ien-Ta-Tsiang- Kiun (the Great Celestial General). All of these are part of Pe-Hou, the White Tiger of Autumn. Koui-siou steps across the center of Andromeda, then across the galaxy Andromeda (Messier 31, or M31), and finally the star Mirach. The appearance of this asterism indicated both the time of the harvest and the need to make footwear. Kiun-nan-mun is near the star Adhil at the right foot of Andromeda. Kiun-nan-mun, along with many other asterisms of this part of the White Tiger, is associated with the end of summer festivals. T'ien-Ta-Tsiang-Kiun is near the star Almech at the left foot of Andromeda. Gamma Andromeda represented the Great Celestial General, while surrounding stars represented his officers. The Marshall Islanders saw a porpoise design in the constellations Cassiopeia, Andromeda, Triangulum, and Aries. The tail of the porpoise is the "W" shape of Cassiopeia, with Aries at the head. Andromeda made up the mid-body and dorsal fin of this ocean mammal. Visually from Earth, Andromeda is found between the Milky Way band of stars and the ecliptic between twenty-three and three hours right ascension, and between twenty and fifty-five degrees north declination. The constellation starts at Alpheratz, or Alpha Andromedae, the north- east star of the Great Square of the mythic winged horse, Pegasus (which is at the head of Andromeda), and continues in a generally northeasterly direction. Delta and Pi Andromedae mark the breasts of Andromeda, Mu Andromedae and Beta Andromedae (also known as Mirach) mark her waist, while 51 Andromedae and Gamma Andromedae (also known as Almech) mark the feet of the chained maiden. Lambda Andromedae marks her right chained hand, while the princess' other hand is vaguely indicated in the opposite direction. Cassiopeia and Lacerta are to the right of Andromeda, while the constellations Triangulum and Pisces are to her left. Pegasus and Perseus are found above and below Andromeda, respectively. Alpheratz, or Alpha Andromedae, is a B9 spectral class spectroscopic binary star system with a period of 97 days. It is a white star of magnitude 2.1 located roughly one hundred light years from Earth. Alpheratz means "the horse's navel", attesting to its former attachment to the constellation of Pegasus, where it was once known as Delta Pegasi. Another bright star of the same magnitude is Mirach, or Beta Andromedae. It is a M0 class star found 170 light years from Sol. Its name means "girdle of the waist-cloth", which approximates its position in the constellation. The third magnitude 2.1 star in Andromeda is Almech, or Gamma Andromedae. It is probably the most interesting of the group. A trinary star system with components of magnitude 2.1, 5.5, and 6.3, it consists of orange (K3), emerald (B9), and blue (A0) members, first recognized as being multiple by Frederich G. W. von Struve (1793-1864) in 1830. The separation of the closer pair in the system is from one to ten seconds of arc. Their orbit has a period of 61 years. Almech is the name of a small predatory animal in Arabia. One of the most significant and stunning object in Andromeda is the galaxy Andromeda (Messier 31, or M31). This spiral star structure is a relatively bright celestial object at magnitude 4.8. The galaxy is found at zero hours, 42 minutes right ascension and 41 degrees north declination. Andromeda is one of the few Messier objects which can be viewed clearly with binoculars, despite being over 2.2 million light years from our Milky Way galaxy. At this distance, Sol would have an apparent magnitude of just 29.1. It should be noted, though, that Andromeda is a next-door neighbor to the Milky Way compared to most other galaxies in the Universe. When the light now seen from Andromeda left on its 730 kiloparsec intergalactic journey, one of humanity's most ancient ancestors, Homo Habilis, were roaming the grassy plains of East Africa. The Andromeda galaxy was first mentioned by the Persian astronomer al-Sufi (903-986) in the Tenth Century and was referred to as the "little cloud". Andromeda is a spiral galaxy which is seen about fifteen degrees from edge on and was initially believed by earlier astronomers to be a cloud of gas or a forming solar system. The true distance of Andromeda was determined in 1923 with the use of Cepheid variable stars. This galaxy contains over three hundred billion suns and the absolute magnitude of the great spiral, almost twice the size of our own Milky Way galaxy, would be -20.3! Sol's apparent magnitude in Earth's sky is -27 for comparison. It is 160 minutes by 40 minutes in diameter, with over one hundred novae having been discovered there since the invention of the astronomical telescope. Andromeda is also a strong celestial radio source at 158.5 megahertz. Twenty-four minutes south of Messier 31 is the galaxy Messier 32, an elliptical companion galaxy. It is faint (magnitude 8.7) and small, only 3.6 by 3.1 minutes in size. M32 was discovered in 1749 by Le Gen- tilin. Another even smaller companion to M31 is Messier 110, thirty- five minutes to the northwest. M110 was discovered in 1773 by Charles Messier (1730-1817) and its stellar magnitude is only 9.4. There are three annual meteor "showers" associated with Andromeda, as they appear to emanate from the constellation. Those occurring on August 31 and October 3 are relatively minor, but the Andromedids of November 14 can be quite impressive. The radiant of these is near Gamma Andromedae, and they are best seen in very dark skies at a usual rate of five to fifteen meteors per hour. This display is thought to be the remains of the comet Biela, which failed to reappear in 1872. In 1885 the Andromedids produced from five thousand to seventy-five thousand meteors per hour! The chained princess of mythology is one of the larger constellations in the Northern sky and possesses one of the most spectacular objects in all of observational astronomy. The history of Andromeda and her many surrounding constellations form a fascinating story, well suited for late night observing sessions under clear and dry autumn skies. References and Further Reading - Allen, Richard H., STAR NAMES: THEIR LORE AND MEANING, Dover Books, New York, 1963 (1899) Bishop, Roy L., OBSERVER'S HANDBOOK, The Royal Astronomical Society of Canada (RASC), 1988 Burnham Jr., Robert, BURNHAM'S CELESTIAL HANDBOOK (three vol.), Dover Books, Mineola, New York, 1978 Menzel, Donald H., and Jay M. Pasachoff, FIELD GUIDE TO THE STARS AND PLANETS, Houghton Mifflin Company, Boston, 1983 Moore, Patrick, EXPLORING THE NIGHT SKY WITH BINOCULARS, Cambridge University Press, 1986 Murdin, Paul, CATALOGUE OF THE UNIVERSE, Crown Publishers, 1979 Staal, Julius D. W., THE NEW PATTERNS IN THE SKY, McDonald and Woodward, Blacksburg, 1988 Staal, Julius D. W., STARS OF JADE, Writ Press, 1984 About the Author - Brian Mason is currently pursuing a Ph.D. in astronomy with CHARA while teaching physics at Avondale High School in Atlanta, Georgia. Brian's interests include binary star astrometry and photometry, as well as speckle interferometry. He is also active in astronomical computing. Brian is the author of "Pegasus: Winged Horse of Autumn" in the September 1990 issue of the EJASA.