Andromeda · Star Almanack

{% capture constellation_story %} ## A story written across the sky Andromeda belongs to a family of constellations whose names preserve a connected Greek story. She is the daughter of Queen Cassiopeia and King Cepheus, and the woman rescued by Perseus from a sea monster. Cetus gives the monster a place in the celestial cast. Recognizing these names turns separate figures on a chart into characters in a shared narrative. The familiar name “the Chained Princess” recalls the moment before her rescue. Andromeda’s figure has often been drawn with arms extended, her wrists bound to the rock. The stars do not dictate that pose: it is an interpretation inherited through storytelling and illustrated maps. ## The boast, the monster, and the rescue In the account preserved by Pseudo-Apollodorus, Cassiopeia claims to surpass the Nereids, the sea nymphs, in beauty. Angered on their behalf, Poseidon sends both flooding and a monster against the kingdom. An oracle declares that the disaster will end only if Andromeda is surrendered to the creature. Her father has her fastened to a rock. Perseus encounters her while returning from his expedition against Medusa. He promises to defeat the monster in exchange for marriage to Andromeda, then kills it and frees her. Her earlier betrothal leads to another conflict: when Phineus and his allies plot against Perseus, he turns them to stone with Medusa’s head. Ancient versions differ. Hyginus attributes the offending boast to Cassiopeia’s praise of her daughter, while Pseudo-Apollodorus makes it the queen’s claim about herself. Other accounts differ in how the monster dies. These are strands of a changing tradition, rather than a single fixed script. ## From a pictured princess to a region of sky Andromeda’s identity survived the transition from traditional celestial pictures to modern astronomical mapping. The International Astronomical Union recognizes constellations as bounded areas, so an object described as “in Andromeda” lies within that region when viewed from Earth. The modern boundaries were approved in 1928 and published in 1930. They settle which constellation contains a position, but they do not prescribe a stick figure. Different atlases can join different stars while representing the same constellation. That distinction explains the separate portrait link here. Our chart shows one selected line drawing within the constellation’s full boundary. This article concerns the name and its history; the chart lets you inspect its shape and neighboring patterns. ## The galaxy beyond the figure The name also belongs to M31, the Andromeda Galaxy, a large spiral galaxy about 2.5 million light-years away. It is named for its apparent location in this constellation. The visible stars used to draw the princess are foreground members of our own Milky Way. Under a sufficiently dark sky, M31 can appear as a faint patch to the unaided eye. Binoculars help reveal its brighter central glow. Its light brings a second scale to Andromeda: a human figure imagined among nearby-looking points, and another galaxy far beyond them. ## Sources - [Chandra X-ray Observatory — Andromeda: the story behind the name](https://www.chandra.cfa.harvard.edu/photo/constellations/andromeda.html) - [Theoi — Perseus: ancient accounts of Andromeda’s rescue](https://www.theoi.com/Heros/Perseus2.html) - [International Astronomical Union — The Constellations](https://www.iau.org/IAU/Astronomy-FAQs/Constellations.aspx) - [NASA Night Sky Notes — Catch Andromeda Rising](https://nightsky.jpl.nasa.gov/documents/918/Oct24_Andromeda_Refresh_20240917_123354.pdf) {% endcapture %}{{ constellation_story | markdownify }}