Cassiopeia is a constellation in the northern sky. It was one of the 48 constellations listed by the 2nd century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. Cassiopeia is easily recognizable due to its distinctive ‘W’ shape formed by five bright stars
Cassiopeia contains two stars visible to the naked eye that rank among the most luminous in the galaxy: ρ Cas and V509 Cas, both of the extremely rare class of yellow hypergiants
source: http://www.crystalinks.com/cassiopeia.html and wikipedia