Interesting Facts About The Constellation Andromeda

Interesting Facts About The Constellation Andromeda
Credit: NASA's Goddard Space Flight Center/DSS

Andromeda is a “V” shaped star constellation which lies close to the north pole, and thus is only visible from the Southern Hemisphere during spring time (October to December), but in the Northern hemisphere can be viewed from August to February. As we will now find out, Andromeda is also part of a family of 9 constellations known as the Perseus Group, 6 of which are named after figures from the Greek legend of Perseus, including Cassiopeia, Cepheus, Andromeda, Perseus, Pegasus, and Cetus.

Mythology Of Andromeda

“She walks in beauty, like the night
Of cloudless climes and starry skies;
And all that’s best of dark and bright
Meet in her aspect and her eyes;
Thus mellowed to that tender light
Which heaven to gaudy day denies.”

Lord Byron (1788 – 1824) was chief among the romantic poets of his age, but he wasn’t talking about the beautiful Andromeda when he composed his classic poem, but if he had lived at the time of the mythical princess, her mother the vain Queen Cassiopeia would certainly have thought Byron’s poem was certainly about her beautiful daughter. Cassiopeia even went so far as to boast that together they were both more beautiful than the Nereids, who were the beautiful sea nymphs that usually accompanied Poseidon, and were also alleged to help out sailors in perilous times.

Poseidon sought to punish Cassiopeia for her vanity and sent the sea monster Cetus to destroy their city of Aethiopia (not the same as modern Ethiopia). King Cepheus and his wife Cassiopeia, more anxious to preserve their kingdom than their family, stripped their daughter naked and chained her to a rock in the harbour so the sea monster would kill her and leave their city alone. Of course that’s the point at which Perseus, returning from just having slain the evil, snake-haired Gorgon, showed up on his winged-horse Pegasus and turned Cetus into stone by showing him the decapitated Gorgon’s head.

Principal Stars

– Alpheratz (Alpha Andromedae), the constellation’s brightest star, is blue subgiant found 97 light-years from Earth with a magnitude of 2.06. It is in actual fact a binary system whose main component is 3.6 times more massive than the Sun, and 200 times more luminous. Alpheratz marks one corner of the Great Square of Pegasus, and at one stage was considered a part of the Pegasus constellation. Alpheratz derives from the Arabic for “the navel of the horse”, while in the constellation of Andromeda it represents the mythological princess’ head.

– Mirach (Beta Andromedae), the second brightest star in the constellation, is a red giant that is big enough, and bright enough that the human eye can detect its colour without a telescope or binoculars. It has a visual magnitude of 2.07, making it the night sky’s 55th brightest star, and is situated 200 light years from our solar system. It is around 50 times bigger than our sun, 4 times more massive, and 1,900 times more luminous.

– Almach (Gamma Andromedae), the constellation’s third brightest star, is a multiple star system found 350 light years away with a magnitude of 2.26. It is also provides one of the finest color contrasts for astronomers, with the system’s yellow star lying close to its dimmer, blue star companion.

Most of Andromeda, however, is composed of many unnamed stars aside from their Phi, Pi, Xi, Gamma, Sigma, Delta (etc.) designations. Xi (Adhil), for instance, is an orange giant, as is 51 And, 56 And and Delta. Conversely, Iota and Omicron are blue giants, while 14 And, Lambda, and the primary of a binary pair named B56 And are all Yellow Giants.

Notable Deep Sky Objects

The Constellation AndromedaOf course, the most popular astronomical object in this constellation is the Andromeda Galaxy (M31) because together with the Milky Way they form the two most massive members of the Local Group with both spiral galaxies having a system of satellite galaxies. (The Local Group: a galaxy group that includes the Andromeda Galaxy, the Milky Way, and the Triangulum Galaxy, as well as more than 54 other mostly dwarf galaxies). The Andromeda Galaxy is a more massive galaxy than the Milky Way, though, and in 2006 the Spitzer Space Telescope revealed M31 contains one trillion stars, more than double the 200 to 400 billion stars in our own galaxy.

The Andromeda Galaxy (M31) has a visual magnitude of 3.4, making it the second brightest Messier Object behind The Pleiades (M45). A more difficult target to observe is the Blue Snowball Galaxy (NGC 7662), which has an apparent magnitude of 8.6, and will look like a fuzzy blue star in a small telescope. In an 18 cm (7 inch) reflector, when equipped with a 75x lens and a Barlow-doubler, though, it becomes a fairly distinctive bluish disk.

Andromeda contains a number of other deep-sky objects (DSOs) of note including several galaxies, such as the dwarf elliptical galaxies M32 and M110; the spiral galaxy NGC 891; a cluster of over 40 galaxies called the NGC 68 Group; the dwarf lenticular galaxy NGC 404; and a pair of interacting spiral galaxies named NGC 90 and NGC 93. The constellation also contains a globular cluster called Andromeda’s Cluster; the open cluster NGC 7686; and the star cloud NGC 206.

Andromedids Meteor Shower

As for meteor showers, Andromeda is very dull. The Andromedids takes place each year from October 26th to November 20th, and on the 8th peaks at less than two meteors per hour. Of course it’s been known to have flare ups, like in December 2011 when it reached 50 per hour, or the storms of 1872 and 1885 where it reached 10,000 per hour. I wouldn’t count on that happening in the near future, although orbital predictions by observers suggest that there might be increased activity in 2018, and then 5 and 18 years beyond that. We’ll have to see.

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