Types of Galaxies :
Astronomers classify galaxies into three major categories :
Elliptical, spiral and irregular. Elliptical:
1. Elliptical galaxies are shaped like a spheriod, or elongated sphere.
2. In the sky where we can only see two of their three dimensions, these galaxies look like elliptical or oval shaped disks.
3. The light is smooth, with the surface brightness decreasing as you go farther out from the centre.
Spiral Galaxies:
1. Spiral Galaxies have three main components : a bulge, disk and halo.
2. The bulge is a spherical structure found in the center of the galaxy.
3. The disk is made up of dust, gas and younger stars.
4. The halo contains old clusters of stars, known as globular clusters.
Irregular Galaxies:
1. Irregular galaxies have no regular or symmetrical structure.
2. They are divided into two groups, I rr I and I rr II.
3. These are mix up of hydrogen gas and dust.
4. All this dust makes is almost impossible to see distinct stars in the galaxy.