Constellation Chart

Cassiopeia

Cassiopeia was the wife of Cepheus, the Ethiopian king, and the mother of Andromeda. The asterism clearly shows the chair upon which Cassiopeia sits. It looks like a shape of "W", and is a guide to find out the Polar Star like the Big Dipper. Japanese had given the asterism names of "The stars of Anchor" or "The stars of shape of mountains", and so on. The constellation is bathed in the faint autumn's Milky Way, so includes various nebulae and star clusters. The dense band of the Milky Way passing through Cassiopeia shows that it lies on the plane of our Galaxy. The familiar W-shaped constellation looks out towards the Galaxy's rim. Cassiopeia's constellation straddles the Milky Way in the far northern sky, neighbouring the constellations dedicated to her husband King Cepheus, her daughter Andromeda, and Andromeda's rescuer Perseus.

Stars

The familiar 'W' of Cassiopeia is made up from five stars, Segin, Ksora, Cih, Schedir and Caph. The central star Cih is the brightest of these (at magnitude +2.2), while Caph is the closest of the five to Earth's Solar System at 55 light years. By a curious coincidence, all five of these stars are variables. In particular, Cih can vary by nearly 5% of a magnitude, and is the prototype of a class of irregular variables, 'Gamma Cassiopeiae' variables, that periodically cast off rings of matter.

Also notable among the stars of Cassiopeia is Achird, a fairly bright star roughly half-way between Cih and Schedir. This yellow binary, though not as bright as some of Cassiopeia's other stars, is much closer to Earth, at roughly nineteen light years' distance.

Star Clusters

Cassiopeia includes a number of open clusters, but none of these is visible to the naked eye. Particularly notable are two Messier objects, M52 and, close to Ksora in the sky, M103. Another cluster, NGC 457, can be found near the distant star Phi Cassiopeiae. All of these clusters are young (no more than 35 million years old), and their distances range between five and ten thousand light years, in the direction of the Galaxy's rim.

Supernovae

Cassiopeia has been the site of two supernovae in historical times. The first occurred in 1572, and reached a maximum magnitude of roughly -4, making it brighter than Venus in the sky. The second took place nearly a century later, leaving a shattered region that is still detectable today, especially by radio telescopes, and is designated Cassiopeia A. These stellar explosions took place about 10,000 light years away.

Nebula's In Cassiopeia

IC1805

There are many gaseous regions and star clusters around the Milky Way flowing from Cepheus, Cassiopeia to Perseus. This attractive reddish nebula, IC1805, is unfortunately invisible with our eyes, but very photogenic and one of the largest ones around this field. The nebula has a span of about one-degree, floating 2500 light years away. IC1805 shows us a bit warped heart-shape. You can see a small and bright region in the upper right-hand side, which has an another number of NGC1795. And the nebula has a neighbor of IC1848 at just east, this couple can be captured with medium-ranged telephoto lenses.

IC1848

IC1848 is a dimmed diffused nebula neighboring IC1805. These nebulae are invisible with our eyes. IC1848 has a size of 60 arc minutes in east-west and 30 minutes in north-south direction. And it's often said that IC1848 looks like a shape of "embryo" turning its head eastward. The body of embryo is brighter than the head, and the region of head includes two fine open clusters of Cr33 and Cr44.

IC59 and IC65

This picture has captured a star field around gamma Cassiopeiae. The bright star is accompanied by very faint reflection nebulae. Though this nebula is single lump of inter-stellar gaseous matter, the Index Catalogue has given two numbers of IC59 and IC65 for the north and northwest parts respectively. Both nebulae has apparent size of about 10 arc minutes and we can detect them only on films with long exposure. IC63 is brighter than IC59, being M-shaped filament structure.

NGC281

NGC281 is a red diffused nebula about 2 degrees east of alpha Cas. Though almost all of diffused nebulae emitting the reddish spectra by the activated hydrogen molecule can hardly be detected with our naked eyes, NGC281 is fairly bright, and you can appreciate its dimmed shape with binoculars in the extremely good conditioned sky. The constellation of Cassiopeia is located in the autumn's Milky Way, and has various attractive and photographed objects including the nebula.

Cluster's In Carina

M52 (NGC7654)

Please try to draw a line from alpha Cas. to beta Cas, then continue this line, doubling its length. You'll be able to find out a beautiful open cluster M52 (NGC7654) in your field of vision. The cluster contains about 120 faint stars gathering like a semicircle, 3800 light years away. It's considered that a supernova explosion in the nebula has formed the characteristic structure. This reddish nebula isn't so well known, but it can be captured with M52, and have made a lively and interesting field in autumn sky.

NGC457

NGC457 is a open cluster about four degrees SE of gamma Cassiopeiae. It has a size of about 13 arc minutes, and seems to be a dimmed nebula surrounding a star with fifth magnitude, phi Cas, by using of binoculars. Although this cluster isn't so popular, it's worthy of note that the cluster looks like a human with arms extended when this picture being upside down. I strongly recommend you to see the cluster with telescopes once, you'll be impressed with its unique shape.

NGC663

Around between delta and epsilon Cassiopeiae, several open clusters are scattered and can be enjoyed only with small binoculars. A large cluster in the center is NGC663, gathering plenty of faint stars in 11 arc minutes. Apparent shape of the cluster looks like a triangle through scopes. And a tiny open cluster at the lower right-hand side is M103, it's wonder that NGC663 wasn't registered in the Messier's catalogue in spite of that NGC663 is larger and brighter than M103.

M103

Messier object M103 is a open cluster which is located in the constellation Cassiopeia. It is a relatively close member of Messier's catalog located 8 thousand light years from earth. M103 is located at 01 33.2 right ascension and 60 42 declination. This Open Cluster has an apparent angular size of 6 and a visual brightness of 7.4. M103 is unnamed and has an NGC catalog number of NGC 581.

NGC7790

NGC7790 is a medium sized open cluster positioned about 2.5 degrees northwest from beta Cas, the western star of W-shaped Cassiopeia. You can see it a bit lower part in this picture. And there is another open cluster of NGC7788 just 16-arc minutes northwest from NGC7790.

NGC7788

These two clusters have an impression like very compact double-clusters. NGC7790 and NGC7788 have apparent diameters of 17 and 9 arc minutes respectively, both have several tens fine stars gathered in sparse. Though you can detect this pair only with compact binoculars, not so striking because they're bathed in the Milky Way.

NGC7635

The remarkably spherical "Bubble" marks the boundary between an intense wind of particles from the star and the more quiescent interior of the nebula. The central star of the nebula is 40 times more massive than the Sun and is responsible for a stellar wind moving at 2,000 kilometers per second (4 million miles per hour or 7 million kilometers per hour) which propels particles off the surface of the star. The bubble surface actually marks the leading edge of this wind's gust front, which is slowing as it plows into the denser surrounding material. The surface of the bubble is not uniform because as the shell expands outward it encounters regions of the cold gas, which are of different density and therefore arrest the expansion by differing amounts, resulting in the rippled appearance. It is this gradient of background material that the wind is encountering that places the central star off center in the bubble. There is more material to the northeast of the nebula than to the southwest, so that the wind progresses less in that direction, offsetting the central star from the geometric center of the bubble. At a distance of 7,100 light-years from Earth, the Bubble Nebula is located in the constellation Cassiopeia and has a diameter of 6 light-years.

To the right of the central star is a ridge of much denser gas. The lower left portion of this ridge is closest to the star and so is brightest. It is experiencing the most intense ultraviolet radiation as well as the strong wind and is therefore being photoevaporated the fastest. The ridge forms a V-shape in the image, with two segments that are aligned at the brightest edge. The upper of these two segments is viewed quite obliquely as it trails off into the back of the nebula. The lower segment comes both toward the observer and off to the side. This lower ridge appears to lie within the sphere described by the bubble but is not actually "inside" the shocked region of gas. Instead it is being pushed up against the bubble like a hand being pushed against the outside of a party balloon. While the edge of the hand appears to be inside the balloon, it is not. As the bubble moves up but not through the ridge, bright blue arcs form where the supersonic wind strikes the ridge to form an apparent series of nested shock fronts.

The region between the star and ridge reveals several loops and arcs which have never been seen before. The high resolution capabilities of Hubble make it possible to examine these features in detail in a way that is not possible from the ground. The origin of this bubble-within-a-bubble" is unknown at this time. It may be due to a collision of two distinct winds. The stellar wind may be colliding with material streaming off the ridge as it is photoevaporated by the star's radiation.

Located at the top of the picture are dense clumps or fingers of molecular gas which have not yet encountered the expanding shell. These structures are similar in form to the columns in the Eagle Nebula, except that they are not being eroded as energetically as they are in that nebula. As in the Eagle, the clumps are seen to emit light because they are being illuminated by the strong ultraviolet radiation from the central star, which travels much faster than the shell and has reached the outer knots long before the expanding rim will.

Maffei 2

This is a nearby spiral galaxy, dramatically dimmed and reddened by dust in the outer disk of the Milky Way; only about 1 per cent of the galaxy's blue light reaches us. Maffei 2 is a very interesting object for study in the infrared and radio regimes, which show it to be a barred spiral galaxy with a nuclear burst of star formation (one of the nearest examples of this process). One of two such galaxies discovered by Paolo Maffei, this is within one degree of the galactic plane in Cassiopeia. Maffei 2 and the giant elliptical galaxy Maffei 1 are so close to us that some workers, such as Gene Byrd and collaborators, have calculated that these galaxies' gravitational influence might have been significant in the early history of our own Local Group galaxies.

NGC185