Cassiopeia is one of the 48 ancient constellations recorded by Ptolemy. She is part of a mythology represented by several major constellations.
Cassiopeia and her husband Cepheus
were queen and king of ancient Ethiopia (which extended over a far greater area than in modern times). Cassiopeia made the mistake of claiming to be more beautiful than any of the sea-nymphs, the Nereids. In retribution, the sea-god Poseidon sent a sea-monster, Cetus
, to ravage the coastline. In an effort to appease the anger of the gods, the king and queen chained their daughter Andromeda to a rock, to be devoured by the monster (see Andromeda
for the rest of the story).
Historical Map of Cassiopeia
A portion of Bayer's 1603 map and drawing of Cassiopeia, showing her as a seated female figure. The very bright star to the left of the figure is Tycho's supernova of 1572, which though having faded away, remained a memorable object in 1603. (Image rotated to a vertical position relative to the original horizontal plates; from the USNO copy of the 1661 edition of Bayer's Uranometria)
Modern Map of Cassiopeia
Wikimedia Commons map by IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)
Constellations Bordering Cassiopeia
Andromeda, Camelopardalis, Cepheus, Lacerta, Perseus
Stars in Cassiopeia
Stars that have common names often have multiple names, so the common names shown (if any) cannot be considered authoritative. Right ascension and declination are given in 2000.0 coordinates.
α Cas (Schedar), RA 00:40:30, Dec +56:32:14. Visual magnitude +2.24, absolute visual magnitude estimated as -2.0, based on distance of 230 light years (4% uncertainty). Color index B-V = +1.17, Spectral Type K0IIIa.
β Cas (Caph), RA 00:09:11, Dec +59:08:59. Visual magnitude +2.3v, absolute visual magnitude estimated as +1.2v, based on distance of 47 light years (8% uncertainty). Color index B-V = +0.34, Spectral Type F2III-IV. Varies in brightness (V 2.25 - 2.31) in 0.10 days.
γ Cas, RA 00:56:42, Dec +60:43:00. Visual magnitude +2.15, absolute visual magnitude estimated as -4.2, based on distance of 600 light years (10% uncertainty). Color index B-V = -0.15, Spectral Type B0.5IVe. Prototype of gamma Cas variables.
δ Cas (Ruchbah), RA 01:25:49, Dec +60:14:07. Visual magnitude +2.7v, absolute visual magnitude estimated as +0.2v, based on distance of 99 light years (2% uncertainty). Spectral type A5V. Eclipsing binary.
ε Cas (Segin), RA 01:54:24, Dec +63:40:12. Visual magnitude +3.38, absolute visual magnitude estimated as -2.3, based on distance of 440 light years (8% uncertainty). Spectral Type B3III.
η Cas AB (Achird), RA 00:49:06, Dec +57:48:55. Visual magnitude 3.4, absolute visual magnitude estimated as +4.6, based on distance of 19.4 light years (1% uncertainty). Binary star. Component A: V = 3.45, B-V = +0.57, Type = G0V. Component B: V = +7.51, B-V = ??, Type = K7V.
Objects of Interest