 AND THERE IS MORE ! Observations by NASA's Hubble Space Telescope       There are two basic types of galaxies, elliptical and spiral. Ellipticals appeared 50 million years after the Big Bang, and 2 billion years later the spirals appeared. The elliptical galaxies are dense and slowly rotating, while the spiral galaxies are more diffuse and rapidly rotating. Edwin P. Hubble classified the galaxies into a Tuning-Fork Classification. An illustration of a relation which is called Meisel's Relation can give an idea about the classification of galaxies. 
Three spiral galaxies M33, M74, and M81 Photographed by NASA's Ultraviolet Imaging Telescope (UIT). |
