SPIRAL GALAXY

The galaxy is a gathering place of stars in the universe. Almost did not find any star that wanders alone in the space between galaxies. And Sun are among 200 billion stars in our Milky Way galaxy (abbreviated with Galactic). Assuming that the average mass of stars in the galaxy is the Sun's mass, the mass of the galaxy can reach 2 x 10 ^ 11 solar masses (the mass of the Sun is 2 x 10 ^ 30 kg).

Milky Way galaxy shapes such as two concave plates are cupped, thick middle part and increasingly flattened towards the edge, and there are spiral arms in it. Therefore, our galaxy is classified into a spiral galaxy. Based on the Hubble galaxy classification, including the Milky Way galaxy SBbc class. This means that our galaxy is a spiral galaxy that has a "bar" or the crossbar in the center, with the brilliance of the central section is relatively similar to the disc, and has a spiral arm structure is somewhat tenuous at the rotation.

Spiral galaxies are composed of three main parts, namely the bulge, halo, and disc. All three have the shape, size, and objects of different authors. In fact, the bulge and disc to be determinant in the classification made by the Hubble galaxy (diagram of a tuning fork). Regions in parts of the galaxy bulge is the most high-density star. stellar halo are stars that are in the halo. But few individual stars found in this section. The more dominant is the group of old stars that the number of member stars reach the millions of pieces, called globular clusters .On the disc there are young stars and interstellar gas and dust located in the spiral arms.