ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel
  • »
  • Education and Science»
  • Astronomy & Space Exploration

Types of Galaxies

Updated on August 23, 2012
The Milky Way seen from Earth.
The Milky Way seen from Earth.

A galaxy is a huge system of stars bound together by gravity. We live in the Milky Way Galaxy, one of billions of galaxies. It is hard to appreciate how immense and enormous our galaxy is because only the closest stars are visible.

Galaxies are classified by shape: spiral, barred spiral, elliptical and irregular.

The Milky Way and about 20 percent of all galaxies are spirals. A spiral galaxy has huge, curved arms formed by stars and gases. The center of the spiral is reddish because of the many red giants there, which are reaching the end of their lives. The spiral's arms are blueish because they contain many bright, young blue stars.

About 10 percent of galaxies are barred spirals. They have two bar-shaped clusters of stars that stretch out from the center.

Most galaxies-60 percent-are elliptical. Most of these are flat and small and do not form new stars. Some elliptical galaxies rotate.

The remaining 10 percent of galaxies are irregular. These are loose collections of stars in no distinct pattern or arrangement. Two irregular galaxies, the Large and Small Magellanic Clouds, orbit the Milky Way galaxy.They were identified by Magellan in 1519,during his famous voyage around the world. He had time, it appears, to explore the skies, too.

Galaxies can be classified by their form and by the types of stars that are found in them.

(Resource: Science Harcourt School Publishers)


A spiral galaxy seen face-on shows a large curved arms of stars.
A spiral galaxy seen face-on shows a large curved arms of stars. | Source
An edge-on spiral galaxy looks like a flattened disk. It contains both old and young stars
An edge-on spiral galaxy looks like a flattened disk. It contains both old and young stars | Source
In edge-on barred spiral galaxies, you can see the bar structure even in a side view.
In edge-on barred spiral galaxies, you can see the bar structure even in a side view. | Source
Irregular galaxies consist mostly of young stars.
Irregular galaxies consist mostly of young stars. | Source
Barred spiral galaxies have bar-shaped features in their center.
Barred spiral galaxies have bar-shaped features in their center. | Source
Elliptical galaxies have an overall lack of form and are made up mostly of old stars.
Elliptical galaxies have an overall lack of form and are made up mostly of old stars. | Source

Comments

    0 of 8192 characters used
    Post Comment

    • saralj profile image
      Author

      Sara A. 5 years ago from Amman, Jordan.

      @RichusFridum Astronomers counted the galaxies in a particular region, and multiplied this to estimate the number for the whole universe. (resource - physics.org)

    • RichusFridum profile image

      RichusFridum 5 years ago from Atlanta, Georgia

      i love the article and the pics

      my only question is how can we know there are billions of galaxies?