Cassiopeia, in astronomy, a constellation of the northern sky easily recognized by a group of five bright stars forming a slightly irregular W. It lies at 1 hour right ascension and 60° north declination. Its brightest star, Shedar (Arabic for “breast”), has a magnitude of 2.2. Cassiopeia is made up of more than 60 stars.
Cassiopeia is a constellation in the northern sky that’s visible all the year in the northern hemisphere but easiest through the longer, darker nights of winter.
Cassiopeia looks like a W, a 3 and finally an M as she makes her way around the north star. SHE IS SEEN AS A QUEEN ON HER THRONE BUT SHE IS UPSIDE DOWN when she first rises above the horizon in the east. Then, dramatically, AS HER LOVER AND GLORIOUS REDEEMER ORION ARISES, SHE IS RIGHTED OR MADE RIGHTEOUS AT HIS APPEARING.
W’ asterism The five brightest stars of Cassiopeia – Alpha, Beta, Gamma, Delta, and Epsilon Cassiopeiae – form the characteristic W-shaped asterism. All five are prominent naked eye stars, three are noticeably variable, and a fourth is a suspected low amplitude variable. The asterism is oriented as a W when below Polaris during northern spring and summer nights. In northern winter, and when seen from southern latitudes, it is “above” Polaris (i.e. closer to the zenith) and the W appears inverted.
Cassiopeia contains many notable deep sky objects, among them the open clusters Messier 52 and Messier 103, the Bubble Nebula, the Heart Nebula and the Soul Nebula, the supernova remnants Cassiopeia A and Tycho’s Supernova, the Owl Cluster, Caroline’s Rose Cluster, and the star-forming cloud popularly known as the Pacman Nebula.
Cassiopeia has 14 stars with known planets and eight named stars. The proper names of stars that have been officially approved by the International Astronomical Union (IAU) are Achird (Eta Cassiopeiae A), Caph (Beta Cassiopeiae), Castula (Upsilon2 Cassiopeiae), Fulu (Zeta Cassiopeiae), Nushagak (HD 17156), Ruchbah (Delta Cassiopeiae Aa), Schedar (Alpha Cassiopeiae), and Segin (Epsilon Cassiopeiae).
The constellation contains two Messier objects: Messier 103 (NGC 581) and Messier 52 (NGC 7654). It is associated with a single meteor shower, the December Phi Cassiopeiids. The Perseid meteor shower is also associated with the constellation.
The best time of the year to see Cassiopeia is during the month of November, when the constellation appears higher above the horizon around 9 pm.
