Ring Galaxies

Ring galaxy is a galaxy, which in form resembles the ring. Ring galaxies are composed of massive, relatively young blue stars that are extremely bright. The central area contains relatively few great matter.
Ring galaxies form when small galaxies collide with a core of spiral galaxies. On the outer edges of the new, combined galaxy formed a powerful ring made up of many stars. Hubble Space Telescope revealed more ring galaxies than scientists expected, indicating the possibility of galactic collisions.
Almost all galaxies have the tendency of gathering in clusters of galaxies. So far there are over 3,000 such clusters. Our galaxy is located in relatively small galactic flock with another 33 galaxies called the Local Group. There are far larger galactic clusters. One of the largest clusters for which we know, lies in the constellation Coma Berenices. It has a flock of over 30,000 galaxies. All of these clusters of galaxies together with all matter and energy makes the galactic group called Metagalaxy. It is assumed that it has about 10 billion galaxies, whose mass is about 10 to 15 solar masses.
Stars and gas clouds orbit the center of the galaxy. Astronomers believe that most galaxies rotate around the black hole, the object which with a large gravitational force attracts everything, even light. Rotation period lasts for more than 100 million years. Space exploration is based on optical surveys. Most of discoveries about the universe came to existence due to hydrogen clouds, which radiate electromagnetic radiation.