Image milky way

The Milky Way

The stars are not isolated in space but group together to form galaxies. Galaxies are nothing more than immense collections of stars and gas. They formed about 13 billion years ago when gigantic gas clouds, made up mainly of hydrogen and helium, contracted.

Our Sun belongs to a galaxy called the Milky Way. The figure shows what the Milky Way looks like from the outside: a kind of wheel, spinning in space. In the centre there is a giant black hole. From this centre long spiral arms branch out. These arms contain gas, dust and stars, whose formation occurred from a few million to several billion years ago.

The Milky Way has a diameter of about 100 thousand light years. Our Solar System is 26 thousand light years away from the centre of the Galaxy, if the entire galaxy were drawn on a single page, even a dot would be too large to represent our Solar System.

All the objects rotate around the centre of the Galaxy. It takes 250 million years for the Sun and all the other bodies in the Solar System to complete a revolution around the centre of the Milky Way.

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