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.
“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.”
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- January 15, 2011 / 10:19 pm