A Galactic Year

A Galactic Year is the time it takes for a star (and the planets of that star) to orbit once around the center of it’s own galaxy. The Galactic Year for this star system (Solar System) is 200 million years.

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“Well, we know that we travel in (roughly) a circle around the center of the Milky Way, and that our radius from the center is about 8 kiloparsecs, or roughly 26,000 light years. That means our Solar System (including the Sun) needs to travel a distance of 1.55 x 1018 kilometers to go around the Milky Way once. If we know how fast the Sun is moving, we can figure out how long a Galactic Year is. Well, we can both measure and calculate its velocity to be 220 kilometers/second, and so we can just do the math, knowing that there are 31,556,952 seconds in a Gregorian Year, and we find that it takes about 223 million years to make one galactic year.”

http://startswithabang.com/?p=1744

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