Spirals, ellipticals and irregulars

Galaxies are enormous families of stars, which lie scattered across the never-ending space of the universe. Each galaxy contains many millions of stars - a mixture of giant and dwarfs stars, old and young stars, and clusters of stars. Some galaxies are spiral in shape, while other are elliptical (like a flattened circle). Those that do not seem to have much of a shape at all are called irregular galaxies. There are countless numbers of galaxies, and they are grouped together in clusters. Our solar system , for example, is part of the MIlky Way Galaxy. This belongs to a collection of galaxies called the Local Group, which contains about 25 galaxies, such as the Large and Small Magellanic Clouds. The Andromeda Galaxy, the largest member of our cluster, is so huge we can see it in a very dark sky without a telescope. It lies more than 2 million light years away from Earth. Light reaching us now from the Andromeda Galaxy began its journey across space long ago when the earliest humans lived on Earth.

	Spiral The arms of a normal spiral galaxy are filled with stars and gas clouds. Spiral galaxies have a central bulge, ot nucleus, from which a number of arms curve out. They are classed as a, b or c depending on how far open the arms happen to be. S0 galaxies are similar to spirals, but have no arms.
	Barred Spiral A barred spiral galaxy has a bar of stars across its cnetre. The spiral arms begin at the ends of the bar. Barred-spiral galaxies, on the other hand have spiral arms that come out of the ends of a line of stars (bar) through the nucleus. They are classed as a, b or c.
	Elliptical Galaxy Giant elliptical galaxies are massive. This galaxy has five trillion stars. Ellipitical galaxies are described by a number from 0 to 7 which indicates how flattened they are.
	Irregular Galaxy Irregular galaxies have random shapes and they are smaller than the Milky Way.

The main index of galaxies

Click the following buttons to view the Simulation of a merger between an elliptical and a spiral galaxy that may have shaped Centaurus A, dissolving to match to the ground-based image of the galaxy. merger2.mov (5369KB) require

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