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Physics and the Cosmos Macrocosmos The Milky Way
The Milky Way
Our galaxy,
the Milky Way, consists of approximately one hundred billion
stars which are kept together by the gravitational force.
It is a spiral galaxy. Our sun is almost in the middle of
the plane of the galaxy, about 8000 parsec (
Picture of the Milky Way from the COBE satellite
The galaxy mainly consists of three parts:
- A disc consisting mainly of younger stars, of which our sun is one. This disc is reddish yellow in the picture. In the spiral arms in this part of the galaxy new stars can be formed.
- The centre, where there is a region of older stars, which is white in the COBE-picture.
- Dark matter around the galaxy. This type of matter cannot be seen in any pictures since it is dark, but one has concluded that it is there from the movement of the stars. In contrast to the visible part of the galaxy, one thinks that the halo is spherically symmetric.