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==Key Stage 3==
===Meaning===
[[File:Galaxy1.png|right|300px|thumb|This [[galaxy]] has over 100 billion [[star]]s.]]
A [[galaxy]] is a group of millions of [[Star|stars]] held together by [[Gravity|gravity]].
===About Galaxies===
: '''Galaxies''' are usually held together by a large [[Black Hole]] at the centre. The [[stars]] all [[orbit]] this central [[Black Hole]].
: [[Scientist]]s believe there are over 200 billion '''galaxies''' in the [[Universe]].