How big is the Milky Way?

You may think it’s a long way down the road to the chemist, but that’s just peanuts to the Milky Way.


Asked by Carol Johnson

With debris, dark matter, dust and up to 400 billion stars, our galaxy has an estimated mass of 3 trillion times our Sun. The Milky Way is a barred spiral galaxy with a flat rotating disc consisting of gas, dust and stars which is estimated to be between 100,000-120,000 light years across. This disc is composed of the familiar spiral arms, one of which plays host to our planet. These spread out from a central bulge with an average thickness of around 2,000 light years, where Earth is located, yet this is nothing compared to the central bulge of our galaxy with a thickness of around 30,000 light years.

Answered by Sophie Allan from the National Space Centre

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