LEVIGNAC Stephane
DOMECQ Audrey
HORNUST Amandine
PETIT Jean
LYCEE BOSSUET DE CONDOM (FRANCE)


 


1- APPEARANCE ON THE SKY

The constellation of Andromeda appears as a double curved line of stars that departs from the northeast angle of the Great Square of Pegasus. It is an important constellation, south of the constellation of Cassiopeia and west of the constellation of Perseus. It does not contain any first magnitude star.
It can be easily found , crossing the constellation of Cassiopeia from Polar Star. In autumn, it can be seen high up in the south-east.

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2- MYTHOLOGY

Andromeda was the daughter of Cassiopeia and Cepheus, king of Ethiopia. Cassiopeia boasted that she and her daughter were more beautiful than any of Poseidon's many nymphs, including the Nereid sea-maidens. The God of the Seas punished the vain mother by sending a monster, the Cetus, to ravage the entire coast of Cassiopeia's homeland. Andromeda was chained , naked, to a rock by the seashore, to be sacrificed to the dreadful sea monster. Whilst awaiting her death, she was rescued by Perseus.

Perseus was passing by, on his winged horse, Pegasus, after slaying the Gorgon Medusa which was so ugly that it turned everything that looked at it to stone. Perseus attracted by Andromeda's beauty decided to release Andromeda , but only if he could marry her afterwards. Cassiopeia and Cepheus had no other choicebut to give their consent..
Perseus showed the head of Medusa to the monster , bewildering and turning it to stone.
He married the princess and the two went on to live a long and happy life together , on the island of Seriphos

Andromeda is represented in the sky as a woman with her arms outstretched and chained at the wrists.
When Cepheus and Cassiopeia died, Poseidon placed them both in the heavens. Now , all five of them, along with Andromeda , Perseus and Pegasus, are immortilized in the sky for ever.
Some writers identify the "whale constellation" with Cetus but a whale is far from being a sea monster!.

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3- THE MAIN STARS

There are three main stars in the constellation of Andromeda, alpha, beta and gamma,all set out in a row , equidistant from one another and with equal luminosity.The first of them is located in the north-eastern angle of Pegasus.
"Then, you have, under your eyes, the victim's body: her hair, her belly and her left heel"

a Alpha Andromedae : Alphératz

The a star , Alpheratz, connects Andromeda with Pegasus. Its arabic name means "the horse'e shoulder" or "the navel of the steed", showing that the star originally belonged more to Pegasus than to Andromeda, as it is today.
With a temperature of about 13 000K, its spectral classification is at the end of the B star range B8 IV. It is a hot , blue star.

It stands at a distance of 97 ligtht years away. Its total luminosity is 110 times more than the sun (200 times if we include ultraviolet radiation)
Alpheratz is different from the others stars in two ways:
· It is a spectroscopic binary.It appears as a single star (magnitude 2,1) in even the most powerful telescopes but the spectral lines split into two at regular intervals. (Period:96,7 days) , proof of a dimmer companion (magnitude 11,3 )
· The main star is also unusual chemically being the brightest member of the "mercury-manganese stars". Compared to our standard star, the sun, its atmosphere have much larger reserves of mercury, manganese, gallium and europium,.

d Delta Andromedae

No peculiar arabic name for this star, orange giant, of magnitude 3,5.
It is , like a Andromedae, a spectroscopic binary located 140 light years from our solar system. Its spectral classification is K3 III for a temperature of about 4 000K

b Bêta Andromedae : Mirach

Mirach is the second brightest star of the constellation for its brightness (Since the three stars line up in order of brightness, it was easy, for Bayer, to assign it the name b.) Its arabic name means "loins".
Its magnitude is moreorless equal to Elpheratz (magn.2) but Mirach is a cool (3 800K) red and bright giant.
From its distance of 200 light years, it shines 470 times more brightly than the sun (and 1900 times more if the infrared radiations are included). Its diameter is about the size of Mercury's orbit (0,8 a.u) and it has a small companion, of 14th magnitude and 60 000 times fainter than the main star , 1700 AU away.
Mirach should die soon (some megayears away !) as a dense white dwarf.

g Gamma Andromedae : Almach

Almach is one of the best examples of double stars. Its name means "desert wild cat", which has almost nothing to do with this constellation. Even with a small telescope, it is easy to see the pair, the brighter being yellow and the other blue. They are named Gamma-1 and Gamma-2.
Gamma-1, of second magnitude, is a spectral class K giant, with a temperature around 4 500K. From its distance of 355 light years, it shines about 2 000 times more brightly than the sun. Its radius is about 80 solar.It is a dying star.
Gamma-2 is a blue-green star , also double. The 2 stars orbit each other in 60 years cycles.The brighter of these two is also double (components very close together, detectable only with the spectrograph, and orbiting every 2,7 days).. These 3 gamma-2 stars are main sequence stars,blue, with a temperature of about 10 000K.

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4- OTHERS STARS

The constellation includes a lot of other stars:
· Some are double stars : Kappa, Pi, Tau,Phi and Omega Andromedae
· Some are variable stars :Zeta, Lambda, Omicron and RX Andromedae
· A peculiar star :Upsilon Andromedae, about 44 light years from earth, is known to have 3 planets in orbit, the first multiple-planet system discovered outside earth's solar system.

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5-
DEEP FIELD OBJECTS

M32

If Andromeda lacks bright stars, it compensates in galaxies and nebulae
M31 is the spiral galaxy known as the Andromeda Galaxy and one of the best known in the deep sky. It is the closest large spiral galaxy to the Milky Way and is visible to the naked eye.
M32 is the brightest elliptical satell M31
ite of M31
M110 is another elliptical galaxy. It can be seen in the same field of view as M32.

 

 

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6- ARTISTIC INSPIRATION
The legend of Andromeda inspired many artists:
a) In literature, Ovide the famous latin poet, made a fictionalized account of it which appeared in the Metamorphoses. Pierre Corneille, created a tragic-opera out of it, in 1650, with great success. Masami Kurumada also took inspiration from Andromeda for his knight in the manga Saint-Seya.

b) In music Guillaume Lekeu, created , in 1881 , a cantata about the chained princess.

c) In art "Andromeda rescued by Perseus" was painted around 1515 by Piero di Cosimo.
Pierre Puget, the French painter sculptor and architect, also created a tapestry, in 1684, entitled "Perseus delivering Andromeda" which is currently exposed in the Louvre in France.

d) On the screen. The American screenwriter Robert Wise was inspired to write his thriller the Andromeda Mystery which appeared on the screens in 1971.

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7- HOW TO OBSERVE ANDROMEDA?

During all september,almost all night. Look to the east at twilight.
From september, Andromeda and Pegasus are visible at sunset. You can easily find The Great Square of Pegasus, with its four bright stars (Markab, Scheat, Algenib and Alpheratz which "belongs" to Andromeda)
Pegasus and Andromeda look like a fake Big Dipper , but larger and on the other side of Polaris.


Visible to the naked eye.
The three brightest stars , lined up in a row and the famous Andromeda galaxy , one of the showpieces of the northern sky, which extends over 3 degrees.

With binoculars
You can catch a glimpse at the cigar-like galaxy and its brighter core

With a telescope
You can see the spiral arms of the galaxy, 2 small elliptic galaxies (M32 on the bottom right edge of M31 and M110 to the top ), Gamma Andromeda which , when spitted, shows an orange primary and a blue companion.

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8- BIBLIOGRAPHY

Websites

http://www.corvus.com/con-page/autumn/and-01.htm
http://edweb.sdsu.edu/people/bdodge/scaffold/zeuslover.html
http://www.bellaonline.com/articles/art4967.asp
http://www.astro.uiuc.edu/~kaler/sow/alpheratz.html
http://www.astro.uiuc.edu/~kaler/sow/mirach.html
http://www.dibonsmith.com/and_con.htm
http://www.glypheb.com/esky/constellations/andromeda.html

Books
Le grand livre du ciel - BORDAS
Constellations GRÜND
Etoiles et constellations de A Benhamouda SNED

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