Andromeda


Transit Date of principal star:
20 July


Andromeda was the daughter of Cepheus and Cassiopeia. Mother thought she and daughter were more beautiful than any of Poseidon's many nymphs, and she taunted the God of the Seas until he just couldn't take it any longer. Poseidon punished the vane mother by chaining her daughter naked to a rock, to be sacrificed to a dreadful sea monster.

Some writers identify this monster with Cetus, another constellation. But I can find no reference in the classical texts that directly name the monster as Cetus. (In fact the very name means "whale", hardly a dreadful sea monster.)

Perseus, fresh from slaying the Gorgon Medusa, was passing by. Attracted by Andromeda's beauty, and no doubt the generally heroic opportunities the situation offered, he agreed to rescue her. But only if he could marry Andromeda afterwards.

Cepheus and Cassiopeia were not anxious for their daughter to wed Perseus, but they had little choice, so agreed. Perseus skimmed over the water, thus confusing the monster, and then cut off the monster's head. The wedding followed soon afterwards.

At the wedding relatives distrupted the proceedings, probably at Cassiopeia's insistence. In the following melee both Cassiopeia and Cepheus lost their life. Poseidon put them both in the heavens (well, it was the least he could do...).

Much later Athene put Andromeda in the same region of the sky, between mother and father.


The asterism consists of the brightest star, Alpheratz (or Sirrah) denoting Andromeda's head, and the rest of the principal stars marking other parts of the young woman's body. But I like to think that the other stars in fact trace Andromeda's flowing hair, and I've drawn the constellation to reflect that idea.

The Bayer stars are not very bright, as the constellation generally ranges from third and fourth magnitude stars.

There are a number of fine binaries and several variables, and some very nice deep sky objects, including perhaps the most famous spiral galaxy of all.


Double stars:

Gamma1 and gamma2 Andromedae form a noted binary with colour contrast, gold and blue.

The binary is a multiple system. AB: 2.5, 5; PA 63, and separation 10".

BC (the primary of which is gamma2) form a very close binary with an orbit of 61 years: 5.5, 6.3; currently the component is at PA 104 and separation 0.5"

Kappa Andromedae is a wide and rather faint binary: 4, 11; 194, 46.8".

Pi Andromedae is alse faint and wide: 4.4, 8.9; 173, 36".

Tau Andromedae: 5, 10; 329, 52.5".

Phi Andromedae has a 370 year orbit: 5, 6.5; 154, 0.5".

Omega Andromedae: 5, 12; 122, 1.9".


Variable stars:

Zeta Andromedae is an EB variable: 3.9-4.1 with period of 17.77 days.

Lambda Andromedae is an RS CVn type variable: 3.7-4.0, 54.2 day period.

Omicron Andromedae is a gamma Cas type variable, ranging from 3.6 to 3.8.

R Andromedae: a Mira type variable with a period of 409.33 days, ranging from 5.8 to 14.9. In 2000 the maximum should occur in April.


Deep Sky Objects:

One of Andromeda's greatest attractions is the spiral galaxy known as M 31. There are also several more deep sky objects worthy of attention.

M31 (NGC 224), "The Andromeda Galaxy", is the finest spiral galaxy in the heavens, and probably the most well known.

The galaxy lies at about a fifteen degree angle from being edge-on; it has a bright oval nucleus. Its distance is approximately 2.3 million light years. Dust lanes become visible in medium-sized telescopes.

M32 (NGC 221) is the brightest elliptical satellite of M31, although rather faint compared to the latter. This galaxy is located almost half a degree to the south of M31 and is best seen in large telescopes.

M110 (NGC 205) is another elliptical galaxy, and a larger companion to M31 but much dimmer. It lies about thirty-five arc-minutes NW of M31.

NGC 752 is an open cluster of perhaps a hundred rather scattered stars. It's about four and a half degrees south of gamma Andromedae, and two degrees west.

NGC 891 is rather faint, but quite a nice edge-on spiral with clearly distinguished dust-lane in large telescopes. It's four degrees due east of gamma Andromedae.

NGC 7662, sometimes called "Blue Snowball", this is a blue-green planetary nebula with a very faint central star which is apparently variable (estimated to range from 12 to 16 visual magnitude). The nebula is found about 2.5 WSW of iota And.


For a closer appreciation of Andromeda, visit the Binocular Section.


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