Cassiopeia

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 bordered by Andromeda to the south, Perseus to the southeast, and Cepheus to the north. It is opposite the Big Dipper, and from northern latitudes can be seen at its clearest in early November. ... The four brightest stars of Cassiopeia are all brighter than the third magnitude. Alpha Cassiopeiae, traditionally called Shedir (from the Arabic Al Sadr, "the breast"), is a double star. The primary is an orange-hued giant of magnitude 2.2, 229 light-years from Earth. The secondary is widely separated from the primary and is of magnitude 8.9. Its traditional name means "the breast". Beta Cassiopeiae, or Caph (meaning "hand"), is a white-hued star of magnitude 2.3, 54 light-years from Earth. 16th-century Arabian astronomer Al Tizini gave this star the name Al Sanam al Nakah, (The Camel's Hump), referring to the contemporaneous Persian figure. The two other notably bright stars in Cassiopeia are both variable stars. Gamma Cassiopeiae is a shell star, a type of variable star that has a very high rate of rotation. This causes the star to be somewhat unstable and periodically eject rings of material. Gamma Cassiopeiae has a minimum magnitude of 3.0 and a maximum magnitude of 1.6; it is currently approximately magnitude 2.2. Delta Cassiopeiae, also known as "Ruchbah" or "Rukbat," meaning "knee," is a Algol-type eclipsing variable star. It varies by 0.1 magnitudes around magnitude 2.7; its period is 2 years and 1 month. Ruchbah appears to have a blue-white hue and it is 99 light-years from Earth. ... Deep-sky objects. Because it lies in rich Milky Way star fields, Cassiopeia contains many deep sky objects, including open clusters and nebulae. Two Messier objects, M52 (NGC 7654) and M103 (NGC 581), are located in Cassiopeia; both are open clusters. M52, once described as a "kidney-shaped" cluster, contains approximately 100 stars and is 5200 light-years from Earth. Its most prominent member is an orange-hued star of magnitude 8.0 near the cluster's edge. M103 is far poorer than M52, with only about 25 stars included. It is also more distant, at 8200 light-years from Earth. Its most prominent member is actually a closer, superimposed double star; it consists of a 7th-magnitude primary and 10th-magnitude secondary. The other prominent open clusters in Cassiopeia are NGC 457 and NGC 663, both of which have about 80 stars. NGC 457 is looser, and its brightest member is Phi Cassiopeiae, a white-hued supergiant star of magnitude 5.0. The stars of NGC 457, arrayed in chains, are approximately 10,000 light-years from Earth. NGC 663 is both closer, at 8200 light-years from Earth, and larger, at 0.25 degrees in diameter. Planetary nebula IC 289 is a cloud of ionised gas being pushed out into space by the remnants of the star’s core. There are two supernova remnants in Cassiopeia. The first, which is unnamed, is the aftermath of the supernova called Tycho's Star. It was observed in 1572 by Tycho Brahe and now exists as a bright object in the radio spectrum. Within the 'W' asterism formed by Cassiopeia’s five major stars lies Cassiopeia A (Cas A). It is the remnant of a supernova that took place approximately 300 years ago (as observed now from Earth; it is 10,000 light-years away), and has the distinction of being the strongest radio source observable outside our solar system. ... NGC 457 is another open cluster in Cassiopeia, also called the E.T. Cluster, the Owl Cluster, and Caldwell 13. ... It has an overall magnitude of 6.4 and is approximately 10,000 light-years from Earth, lying in the Perseus arm of the Milky Way. ... Two members of the Local Group of galaxies are in Cassiopeia. NGC 185 is a magnitude 9.2 elliptical galaxy of type E0, 2 million light-years away. Slightly dimmer and more distant NGC 147 is a magnitude 9.3 elliptical galaxy, like NGC 185 it is an elliptical of type E0; it is 2.3 million light-years from Earth. Though they do not appear in Andromeda, both dwarf galaxies are gravitationally bound to the far larger Andromeda Galaxy. ... Meteor showers. The December Phi Cassiopeiids are a recently discovered early December meteor shower that radiates from Cassiopeia. Phi Cassiopeiids are very slow, with an entry velocity of approximately 16.7 kilometers per second. The shower's parent body is a Jupiter family comet, though its specific identity is unknown. [Cassiopeia (constellation). Wikipedia]