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Galaxies and Nebulae: Galaxies |
 Home  Stars  Planets  Satellites  Galaxies and Nebulae 
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Stars live together in "Star Cities" called galaxies. These enormous collections of stars started off as huge clouds of gas soon after the birth of the Universe. Gravity eventually pulled the gas nto separate stars. Galaxies are so vast that it takes starlight hundreds of thousands of years to travel from one side to the other. There are four main types of galaxies- Spirals (like the Milky Way), barred spirals, ellipticals, and irregulars. Spiral Galaxies contain young and old stars. They are disc shaped with spiral arms. In a barred spiral, the arms come out from the ends of a bar across the centre of the galaxy. Elliptical galaxies are flattened ball-shaped collections of old stars (stars at the end of ther life). They are the most common type of galaxy in the Universe. Irregular galaxies are those that have not formed into a specific shape. They are the rarest type of galaxy in the Universe. Milky Way The milky way is a spiral galaxy with a concentration of stars at its centre. This gives the galaxy a central bulge from which arms of stars radiate out. We live in one of these arms. Like all galaxies, the Milky Way is moving. Not only is the whole galaxy travelling through space, but the stars within it are continuously movng around the galactic centre.
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