How big is our galaxy?
The Milky Way's disk spans at least 100,000 light-years and probably contains several hundred billion stars, which makes our home galaxy a giant. However, the Milky Way is surrounded by a "halo" of cold dark matter, which produces no detectable energy but that reveals its presence by exerting a gravitational pull on the visible matter around it. The dark matter probably consists of some type of subatomic particle created in the Big Bang. This halo probably spans 250,000 light-years, and perhaps a great deal more.
The average radius of our galaxy, The Milky Way, is about 50,000 light years. To put that in perspective, if a commercial airliner, let’s say a Boeing 747 flew at a speed of 600mph then it would take approximately 50 billion years to fly from the centre to the edge. So to get from one end to the other, it would take 100 billion years in the plane. Our universe is only 14 billion years young...
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