Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is easily recognizable due to its distinctive 'W' shape, formed by five bright stars. It is opposite the Big Dipper. In northern locations above 34ºN latitude it is visible year-round and in the (sub)tropics it can be seen at its clearest from September to early November. Even in low southern latitudes below 25ºS it can be seen low in the North.

At magnitude 2.2, Alpha Cassiopeiae, or Schedar, is generally the brightest star in Cassiopeia, though is often shaded by Gamma Cassiopeiae, which has brightened to magnitude 1.6 on occasion. The constellation hosts some of the most luminous stars known, including the yellow hypergiants Rho Cassiopeiae and V509 Cassiopeiae and white hypergiant 6 Cassiopeiae. The semiregular variable PZ Cassiopeiae is one of the largest known stars. In 1572, Tycho Brahe's supernova flared brightly in Cassiopeiae. Fourteen star systems have been found to have exoplanets, one of which—HR 8832—is thought to host seven planets.

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