Cassiopeia (constellation)
Cassiopeia is a constellation and asterism in the northern sky named after the vain queen Cassiopeia, mother of Andromeda, in Greek mythology, who boasted about her unrivaled 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.
Cassiopeia in her chair, as depicted in Urania's Mirror
Cassiopeia in the night sky
Kappa Cassiopeiae and its bow shock. Spitzer infrared image (NASA/JPL-Caltech)
Planetary nebula IC 289 is a cloud of ionised gas being pushed out into space by the remnants of the star's core
An asterism is an observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the 88 formally defined constellations. Constellations are based on asterisms, but unlike asterisms, constellations outline and today completely divide the sky and all its celestial objects into regions around their central asterisms. For example, the asterism known as the Big Dipper comprises the seven brightest stars in the constellation Ursa Major. Another is the asterism of the Southern Cross, within the constellation of Crux.
A picture of stars, with a group of appearingly bright blue and white stars. The bright stars together are identified as the asterism Coathanger resembling a coathanger, in the constellation Vulpecula.
Three Leaps of the Gazelle asterism
The "Teapot" asterism in Sagittarius. The Milky Way appears as "steam" coming from the spout.
The "37" or "LE" of NGC 2169, in Orion. It is visible with binoculars.
