Galaxies
What are galaxies?
A galaxy is a very large group of stars held together by gravity. How enormous a galaxy is and how many stars it contains is impossible for us to really understand. A galaxy contains up to a few billion stars!
Our Galaxy is called the Milky Way, named by the Greeks a long time ago. Our type of galaxy is called large barred spiral. We will look at the features of different galaxies below.
Types of Galaxy
Elliptical
Elliptical galaxies are egg shaped. The smallest elliptical galaxies are as small as some globular clusters. Giant elliptical galaxies can contain over a trillion stars. Elliptical galaxies are reddish to yellowish in color because they contain mostly old stars.
Spiral
Spiral galaxies are rotating disks, In the center is a dense bulge of material. Several spiral arms come out from the center. Spiral galaxies have lots of dust and gas and young stars. Andromeda is our closest spiral galaxy at 2,500,000 light years away.
Barred Spiral
These are like spiral galaxies but the have a bar shape of stars in the central bulge. The arms of the spiral normally form at the ends of the bar. The Milky way is this type of galaxy.
Irregular
Galaxies that are not elliptical or spiral or have a regular shape are called irregular. They were likely to have been one of those shapes but has been changed by gravitational attraction or a collision with another galaxy.
Perculiar
These are like irregular galaxies but they have unusual shapes or strange shapes i.e. not a ‘blob’ shape. Again these can form from collisions with other galaxies
Lenticular
Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore are not forming very many new stars. They may still have lots of dust. As a result, they consist mainly of aging stars.
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