Cassiopeia (abbreviation: Cas), the Queen, mother of Andromeda, is a large northern constellation with a distinctive "W" shape marked by five stars of the third magnitude, and with the Milky Way as a backdrop. It lies near Cepheus and not far from the north celestial pole.

 

A binocular sweep of the region is rewarding (especially around Delta Cas) and small instruments reveal an interesting assortment of nebulae and open clusters. See below for details of the constellation's brightest stars and interesting deep sky objects.

 

Heart Nebula

 

 

The Heart Nebula (IC 1805) is an emission nebula located in the Perseus Arm of our galaxy in Cassiopeia. It lies about 7,500 light-years away. The brightest part of the nebula – the bright region near the center – is classified separately as NGC 896, because it was the first part to be discovered. An open cluster in the central region, called Melotte 15, contains some stars up to 50 times as massive as the Sun.

 

Right ascension: 02h 32m 35.57s, declination: +61° 29' 2.3"; apparent magnitude: 18.3; apparent dimensions: 60' × 60'.

 

Stars in Cassiopeia brighter than magnitude 4.0
Star	Visual mag.	Abs. mag.	Spectral type	Distance (lt-yr)	R.A. (h m s)	Dec. (° ' ")
Alpha (Shedar)	2.24	-1.99	K0IIa	229	00 40 30	+56 32 15
Gamma Cassopeiae	2.15v	-4.22	B0IVe	613	00 56 43	+60 43 00
Beta (Caph)	2.28	1.16	F2III-IV	54	00 09 11	+59 08 59
Delta (Ruchbach)	2.66	0.24	A5III-IVv	99	01 25 49	+60 14 07
Epsilon (Segin)	3.35	-2.31	B3III	442	01 54 24	+63 40 13
Eta (Achird)	3.46	-4.73	G0V+dM0	1,410	00 49 06	+57 48 58
Zeta	3.69	-2.63	B2IV	597	00 36 58	+53 53 49

 

Other objects of interest
Name	Type of object	Notes
Bubble Nebula	planetary nebula	NGC 7635. See separate entry
Cassiopeia A	supernova remnant	See separate entry
IC 59	diffuse nebula	Nebulosity associated with Gamma Cas, consisting of two fans pointing northwest. Magnitude 9.9; diameter 10'; R.A. 0h 57.5m, Dec. +61° 09'
NGC 281	diffuse nebula	One degree west of Shedar. Magnitude 7; diameter 35'; R.A. 0h 52.8m, Dec. +56° 37'
M52 (NGC 7654)	open cluster	Kidney-shaped, containing over 100 stars, with a prominent magnitude 8 star at one edge. A good object for binoculars. Magnitude 6.9; diameter 13'; R.A. 23h 24.2m, Dec. +61° 35'
M103 (NGC 581)	open cluster	A fan-shaped cluster with at least 40 stars. Magnitude 7.4, diameter 6'; R.A. 01h 33.2m, Dec. +60° 42'
NGC 457	open cluster	One of the brightest open clusters in the sky and an attractive object for small telescopes. Its stars appear to be arranged in chains. Magnitude 6.4; diameter 13'; R.A. 01h 19.1m, Dec. +58° 20'
Cassiopeia Dwarf	galaxy	See separate entry

 

Constellations

Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Bootes | Caelum | Camelopardalis | Cancer | Canes Venatici | Canis Major | Canis Minor | Capricornus | Carina | Cassiopeia | Centaurus | Cepheus | Cetus | Chamaeleon | Circinus | Columba | Coma Berenices | Corona Austrina | Corona Borealis | Corvus | Crater | Crux | Cygnus | Delphinus | Dorado | Draco | Equuleus | Eridanus | Fornax | Gemini | Grus | Hercules | Horologium | Hydra | Hydrus | Indus | Lacerta | Leo | Leo Minor | Lepus | Libra | Lupus | Lynx | Lyra | Mensa | Microscopium | Monoceros | Musca | Norma | Octans | Ophiuchus | Orion | Pavo | Pegasus | Perseus | Phoenix | Pictor | Pisces | Piscis Austrinus | Puppis | Pyxis | Reticulum | Sagitta | Sagittarius | Scorpius | Sculptor | Scutum | Serpens | Sextans | Taurus | Telescopium | Triangulum | Triangulum Australe | Tucana | Ursa Major | Ursa Minor | Vela | Virgo | Volans | Vulpecula