Cassiopeia is one of the rare constellations which its name is inspired by the name of someone, and in this case, it is the queen Cassiopeia in Greek mythology. She was arrogant and thought her beauty was unrivalled in the ancient myths. This constellation was also listed in the 48 constellations of Ptolemy, and still makes the list among the 88 modern constellations.
Alpha Cassiopeiae (Schedar, derived from the Arabic word Al Sadr which means breast) is the brightest star of Cassiopeia (of magnitude 2.2), but there are occasions during which it is outshone by the variable Gamma Cassiopeiae (of magnitude 1.6). Alpha Cassiopeiae is a multiple stellar system and is composed of four stars. Beta Cassiopeiae (commonly called Caph that means hand) is a white-hued star fairly close to Earth (55 light-years away). Although perhaps not that famous, Cassiopeia contains some of the brightest stars discovered or some generally interesting cases. Among the bright stars, we mention the yellow hypergiants Rho Cassiopeiae and V509 Cassiopeiae and the white hypergiant 6 Cassiopeiae. The famous Tycho Brahe’s supernova which flared in 1572 is also located in Cassiopeia constellation. This is a remarkable supernova because it was among the eight supernovae visible to naked eye historically. A supernova is the energetic explosion of a star which its afterglow can be seen for days (depending on how energetic it would be).
The variable stars of Cassiopeia are: 50 Cassiopeiae, Zeta Cassiopeiae, Theta Cassiopeiae, Iota Cassiopeiae (a triple star system), Omicron Cassiopeiae (another triple star), Eta Cassiopeiae (which is a spectroscopic binary). The last one is also an RS Canum Venaticorum variable which means the binary components own active chromospheres leading to the emergence of stellar spots. Kappa Cassiopeiae is another particular star of Cassiopeia which is a runaway star, and a blue supergiant. Due to its strong magnetic field and wind of particles, it is surrounded by a visible bow shock colliding with the interstellar gas and dust (see figure below). This bow shock is relatively huge in dimension, it covers an area of 12 light-years long and 1.8 light-years wide.
Cassiopeia A which is the brightest extrasolar radio source in the sky is also located in this constellation and is a supernova remnant. There are fourteen stellar systems that host exoplanets in Cassiopeia constellation. Since a rich section of Milky Way flows through Cassiopeia constellation, it contains several open clusters: M52 (NGC 7654), NGC 457, NGC 457, NGC 663, and M103 (NGC 581).
There are also binary stars belonging to Cassiopeia constellation: Sigma Cassiopeiae and AO Cassiopeiae. Psi Cassiopeiae is a triple star belonging to this constellation, located 193 light-years from Earth. There are also yellow hypergiants which are among the most luminous stars of our galaxy: Rho Cassiopeiae and V509 Cassiopeiae. PZ Cassiopeiae which is one of the largest stars known to date also resides in Cassiopeia constellation.
The irregular galaxy IC 10 is also located in the Cassiopeia constellation, and is a starburst galaxy which means it is a star factory at a high rate.
Heart Nebula and Soul Nebula are neighboring nebulae in Cassiopeia constellation.
