Galaxy part 2

Types of Galaxies
   

    Galaxy, as with other objects in the universe has the size, shape, mass, and luminosity that varies. There are three forms of bentul spiral galaxies, elliptical, and irregular shape, but most of the three is the type of spiral and elliptical.

 
a. Spiral Galaxy

Figure 1. M51 Galaxy

             One example is a spiral galaxy of our Milky Way galaxy. This spiral galaxy consists of core, disc, halo, and the spiral arms. The material in the form of interstellar gas and dust clouds are generally found in the spiral arms of galaxies. Also often seen the bright nebula and the absorption of light by interstellar dust. Spiral arms contain young blue stars, including giants very bright. 



             Open star cluster can be seen in the nearest spiral arm, and most of the globular clusters seen in the halo. Spiral galaxy contains many young stars and old stars. In addition to the Milky Way galaxy and Andromeda galaxy, some other spiral galaxies are prominent among: other galaxies and galaxy M.51 M.33. 



A small spiral galaxy appeared as a rotating shaft through the core, and a new spiral-shaped arm starting at the end of the rod. Therefore this type of galaxy spiral galaxy called the stem. This spiral stem sometimes contain interstellar matter and young stars. Diameter spiral galaxies between 20,000 and 100,000 light years and hello stretches far greater than the diameter piringannya. The period of spiral galaxies between 109 to 1012 solar masses.

Figure 2. M33 Galaxy

b. Elliptical galaxy

            More than two thirds of the galaxy stood out in the skies is included in the spiral galaxy. But in fact most of the galaxies in this universe of space luminositasnya relatively low, so that is not visible from a distance is very large. Most dwarf galaxies are classified as type elliptical galaxy.Furthermore, many star clusters mainly contained in these elliptical galaxies. So in fact an elliptical galaxy is far more than any other type spiral galaxies. 

             Elliptical galaxy is speris or ellipsoidal system which consists almost entirely of old stars.Elliptical galaxies are more like the core and halo components of spiral galaxies. There is no bright nebula found in this elliptical galaxy. Most stars are concentrated toward its center, while the more spread out very rarely extends over very large distances so it is not clearly defined in space. That is why it is difficult to determine the size of this elliptical galaxy. Elliptical galaxies form does not indicate that the disk-shaped galaxy is rotating slowly, not as fast as the rotation of spiral galaxies.

             Elliptical galaxies have a size, mass, and luminositasnya in a much larger range of spiral galaxies. For example galaxy M.87, luminositasnya larger than the known spiral galaxy, such as the Andromeda galaxy. Likewise, the mass can reach the 1013 solar masses. But the galaxy Leo II, is a dwarf elliptical galaxy with a luminosity of about 106 luminosity of the Sun and its diameter is about 5000 light years. Ni galaxy about 750,000 light-years away.

Figure 3. Elliptical Galaxy (Cen A Galaxy)