Andromeda (constellation) in the context of 3C 66A

In Greek mythology, Andromeda (/ænˈdrɒmɪdə/; Ancient Greek: Ἀνδρομέδα, romanized: Androméda or Ἀνδρομέδη, Andromédē) is the daughter of Cepheus, the king of Aethiopia, and his wife, Cassiopeia. When Cassiopeia boasts that she (or Andromeda) is more beautiful than the Nereids, Poseidon sends the sea monster Cetus to ravage the coast of Aethiopia as divine punishment. Queen Cassiopeia understands that chaining Andromeda to a rock as a human sacrifice is what will appease Poseidon. Perseus finds her as he is coming back from his quest to decapitate Medusa, and brings her back to Greece to marry her and let her reign as his queen. With the head of Medusa, Perseus petrifies Cetus to stop it from terrorizing the coast any longer.

As a subject, Andromeda has been popular in art since classical antiquity; rescued by a Greek hero, Andromeda's narration is considered the forerunner to the "princess and dragon" motif. From the Renaissance, interest revived in the original story, typically as derived from Ovid's Metamorphoses. The story has appeared many times in such diverse media as plays, poetry, novels, operas, classical and popular music, film, and paintings. A significant part of the northern sky contains several constellations named after the story's figures; in particular, the constellation Andromeda is named after her.

Perseus is a constellation in the northern sky, named after the Greek mythological hero Perseus. It is one of the 48 ancient constellations listed by the 2nd-century astronomer Ptolemy, and among the 88 modern constellations defined by the International Astronomical Union (IAU). It is located near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west. Some star atlases during the early 19th century also depicted Perseus holding the disembodied head of Medusa, whose asterism was named together as Perseus et Caput Medusae; however, this never came into popular usage.

The galactic plane of the Milky Way passes through Perseus, whose brightest star is the yellow-white supergiant Alpha Persei (also called Mirfak), which shines at magnitude 1.79. It and many of the surrounding stars are members of an open cluster known as the Alpha Persei Cluster. The best-known star, however, is Algol (Beta Persei), linked with ominous legends because of its variability, which is noticeable to the naked eye. Rather than being an intrinsically variable star, it is an eclipsing binary. Other notable star systems in Perseus include X Persei, a binary system containing a neutron star, and GK Persei, a nova that peaked at magnitude 0.2 in 1901. The Double Cluster, comprising two open clusters quite near each other in the sky, was known to the ancient Chinese. The constellation gives its name to the Perseus Cluster (Abell 426), a massive galaxy cluster located 250 million light-years from Earth. It hosts the radiant of the annual Perseids meteor shower—one of the most prominent meteor showers in the sky.

De astronomia (Latin: [deː äs̠t̪rɔˈnɔmiä]; Concerning Astronomy) is a book of stories written in Latin, probably during the reign of Augustus (c. 27 BC – AD 14). Attributed to "Hyginus", the book's true author has been long debated. However, the art historian Kristen Lippincott argues that the author was likely Gaius Julius Hyginus, who served as the superintendent of the Palatine library under Caesar Augustus.

The text describes 47 of the 48 Ptolemaic constellations, centering primarily on the Greek and Roman mythology surrounding the constellations, though there is some discussion of the relative positions of stars. The stories it contains are chiefly based on Catasterismi, a work that was traditionally attributed to Eratosthenes.

NGC 169 is an unbarred spiral galaxy located in the constellation Andromeda. It was discovered on September 18, 1857, by R. J. Mitchell.

NGC 169 has a smaller companion named NGC 169A, also designated IC1559. The two are currently interacting, and the pair is included in Halton Arp's Atlas of Peculiar Galaxies.

Alpheratz is a prominent star system in the constellation of Andromeda. Pronounced /ælˈfɪəræts/, it has the Bayer designation Alpha Andromedae, Latinised from α Andromedae, and abbreviated Alpha And or α And, respectively. Alpheratz is the brightest star in the constellation when Mirach (β Andromedae) undergoes its periodical dimming. Immediately northeast of the constellation of Pegasus, it is the upper left star of the Great Square of Pegasus. It is located at a distance of 97 light-years from Earth.

Although it appears to the naked eye as a single star with overall apparent visual magnitude +2.06, it is actually a binary system composed of two stars in close orbit. The chemical composition of the brighter of the two stars is unusual as it is a mercury-manganese star whose atmosphere contains abnormally high abundances of mercury, manganese, and other elements, including gallium and xenon. It is the brightest mercury-manganese star known.

Gamma Andromedae is a multiple star system in the northern constellation of Andromeda. It is the third-brightest star in the constellation, after Alpheratz and Mirach. Its identifier is a Bayer designation that is Latinized from γ Andromedae, and is abbreviated Gam And or γ And, respectively. The system has the proper name Almach, pronounced /ˈælmæk/. Based on parallax measurements, it is estimated to be about 390 light-years distant. The system is drifting closer to the Sun with a radial velocity of −11.7 km/s.

Mirach is a prominent star in the northern constellation of Andromeda. It is pronounced /ˈmaɪræk/ and has the Bayer designation Beta Andromedae, which is Latinized from β Andromedae. This star is positioned northeast of the Great Square of Pegasus and is potentially visible to all observers north of latitude 54° S. It is commonly used by stargazers to find the Andromeda Galaxy. The galaxy NGC 404, also known as Mirach's Ghost, is seven arcminutes away from Mirach.

This star has an apparent visual magnitude of around 2.07, varying between 2.01 and 2.10, which at times makes it the brightest star in the constellation. Based upon parallax measurements, it is roughly 197 light-years (60 parsecs) from the Solar System. Its apparent magnitude is reduced by 0.06 by extinction due to gas and dust along the line of sight. The star has a negligible radial velocity of 0.1 km/s, but with a relatively large proper motion, traversing the celestial sphere at an angular rate of 0.208″·yr.

Messier 32 (also known as M32 and NGC 221) is a dwarf "early-type" galaxy about 2,490,000 light-years (760,000 pc) from the Solar System, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil in 1749.

The galaxy is a prototype of the relatively rare compact elliptical (cE) class. Half the stars are concentrated within the inner core, which has an effective radius of 330 light-years (100 pc). Densities in the central stellar cusp increase steeply, exceeding 3×10 M_☉ pc (30 million solar masses per cubic parsec) at the smallest sub-radii resolved by Hubble Space Telescope, and the half-light radius of this central star cluster is around 6 pc (20 light-years). Like more ordinary elliptical galaxies, M32 contains mostly old faint red and yellow stars with practically no dust or gas and consequently no current star formation. It does, however, show hints of star formation in the relatively recent past.

NGC 891 (also known as Caldwell 23, the Silver Sliver Galaxy, and the Outer Limits Galaxy) is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus.

The object is visible in small to moderate size telescopes as a faint elongated smear of light with a dust lane visible in larger apertures.

NGC 7662 is a planetary nebula located in the northern constellation Andromeda. It is known as the Blue Snowball Nebula, Snowball Nebula, and Caldwell 22. This nebula was discovered October 6, 1784 by the German-born English astronomer William Herschel. In the New General Catalogue it is described as a "magnificent planetary or annular nebula, very bright, pretty small in angular size, round, blue, variable nucleus". The object has an apparent visual magnitude of 8.3 and spans an angular size of 32″ × 28″. Parallax measurements give a distance estimate of 5,730 ± 340 ly (1,757 ± 103 pc).

NGC 7662 is a popular planetary nebula for casual observers. A small telescope will reveal a star-like object with slight nebulosity. A 6" telescope with a magnification around 100x will reveal a slightly bluish disk, while telescopes with a primary mirror at least 16" in diameter may reveal slight color and brightness variations in the interior.

2 Andromedae, abbreviated 2 And, is a binary star system in the northern constellation of Andromeda. 2 Andromedae is the Flamsteed designation. It is a faint star system but visible to the naked eye with a combined apparent visual magnitude of 5.09. Based upon an annual parallax shift of 7.7 mas, it is located 420 light years away. The binary nature of the star was discovered by American astronomer Sherburne Wesley Burnham at Lick Observatory in 1889. The pair orbit each other over a period of 74 years with a high eccentricity of 0.8.

The magnitude 5.26 primary, designated component A, is an A-type main-sequence star based on a stellar classification of A1V or A2V, although it may have already left the main sequence. It was identified as a candidate Lambda Boötis star, but this was ruled out by Paunzen et al. (2003) as it doesn't match the typical characteristics of these objects. Although 2 Andromedae does not display a significant infrared excess, it is a shell star that displays varying absorption features due to circumstellar dust grains. This may indicate it has an orbiting debris disk containing gas that is being viewed edge-on. The star is about 100 million years old and is spinning rapidly with a projected rotational velocity of 212 km/s.

MUL.APIN (𒀯𒀳) is the conventional title given to a Babylonian compendium that deals with many diverse aspects of Babylonian astronomy and astrology.It is in the tradition of earlier star catalogues, the so-called Three Stars Each lists, but represents an expanded version based on more accurate observation, likely compiled around 1000 BCE.The text lists the names of 66 stars and constellations and further gives a number of indications, such as rising, setting and culmination dates, that help to map out the basic structure of the Babylonian star map.

The text is preserved in a 7th-century BCE copy on a pair of tablets, named for their incipit, corresponding to the first constellation of the year, APIN "The Plough", identified with stars in the area of the modern constellations of Cassiopeia, Andromeda and Triangulum according to the compilation of suggestions by Gössmann and Kurtik. Recently, it has been suggested to identify with Cassiopeia only.