Cassiopeia is a constellation in the northern hemisphere, first charted by the Greek astronomer Ptolemy in the 2nd century. It is taken to represent the queen Cassiopeia of the mythical kingdom Ethiopia. In Greek mythology, Cassiopeia offended the Nereids (sea nymphs) by boasting about being more beautiful than them. As punishment for her vanity, she had to sacrifice her daughter Andromeda to appease the sea monster Cetus sent by Poseidon. It is said that, once placed in the sky, Cassiopeia was condemned to circle the celestial pole forever, sometimes hanging upside down, as additional punishment. The constellation is quite easy to spot in the sky because five of its bright stars form a distinctive 'W' shape.
The constellation Cassiopeia occupies an area of 598 square degrees and contains three stars with known planets. It can be seen at latitudes between +90° and -20° and is best visible at 9 p.m. during the month of November.
beta Cassiopeiae or Caph ("palm") is a yellow-white giant with a magnitude of 2.28, classified as a Delta Scuti type variable. It is twice the size of the Sun and 28 times brighter.
alpha Cassiopeiae, Shedir or Shedar ("the breast") has a magnitude of 2.25 and is the second brightest star in the constellation. It is an orange giant more than 500 times brighter than the Sun.
gamma Cassiopeiae is the central star of the constellation. It is an eruptive variable star. It does not have a traditional Latin or Arabic name, but the Chinesse call it Tsih ("the whip"). At maximum intensity (currently 2.15), the star outshines both alpha and beta Cassiopeiae. Gamma Cassiopeiae spins very rapidly and bulges along the equator, which causes it to lose mass. As a result, a disk forms around the star which is responsible for the variations in brightness and emissions.
delta Cassiopeiae, also known as Ksora or Ruchbah ("knee") is an eclipsing binary star about 99 light-years distant. It has an apparent visual magnitude that varies between 2.68 and 2.71.
epsilon Cassiopeiae, also called Segin, is a blue-white giant about 442 light-years away from Earth. Its luminosity is 720 times that of the Sun.
rho Cassiopeiae and V509 Cassiopeiae are among the most luminous stars visible to the naked eye in the galaxy. 
eta Cassiopeiae is a binary star consisting of a yellow dwarf similar to our Sun and an orange dwarf.
Cassiopeia also has two notable Messier objects, both open star clusters. Messier 52 or NGC 7654 was discovered by Charles Messier in 1774 and can be seen with binoculars. In stronger telescopes, it appears as a rich, V-shaped cluster of faint stars with a bright yellow star on the edge.
Messier 103 or NGC 581 was the last Messier object to be catalogued by Charles Messier himself. At about 8,000 light-years away, it is one of the more remote open clusters to be catalogued. It contains between 40 and 50 stars, the brightest one of which is Struve 131 or HD 9311. The cluster is faint, but once found, it has the appearance of curving star chains streaming outward from the centre.
Tycho's Star or CN 1572, observed as a supernova in 1572 and documented by the Danish nobleman and astronomer Tycho Brahe, is also located in Cassiopeia. The star named Tycho G is being studied as a possible companion to the star that created the supernova. The other supernova remnant in the constellation is Cassiopeia A, the strongest radio source outside our solar system that can be observed. The cloud of material left over from the supernova is now about 10 light-years across.
Finally, the constellation contains an irregular galaxy, IC 10, first discovered by Lewis Swift in 1887. It is somewhat difficult to study because, located near the Milky Way plane, it is obscured by interstellar matter. With an exceptionally high rate of star formation, however, IC 10 is known as the only starburst galaxy in the Local Group.
Cassiopeia belongs to the Perseus family of constellations, along with Cepheus
Constellations directly bordering Cassiopeia are Camelopardalis