The Milky Way's Astronomical Numbers
100,000 - Diameter of the Milky Way, in light-years. It's also around 1,000 light-years thick, and that's just the main stellar disk. One light-year is a little less than 6 trillion miles (10 trillion km), so we're talking about a very big disk. In fact, if our solar system was just the size of a coin in your pocket, the Milky Way would still be the size of the United States. 26,000 - Distance from our solar system to the Milky Way's center, in light-years. Astronomers think our solar system completes an orbit around the galaxy's center once every 225 to 250 million years. That means it was just one "galactic year" ago when the dinosaurs began to appear on Earth. 2.6 million - Low-end estimate of the number of suns it would take to equal the mass of the supermassive black hole that lurks at our galaxy's center. The sun is roughly 333,000 times more massive than Earth. So, it would take at least 858 billion Earths to equal that black hole's mass. Of course, no one can see the black hole. But astronomers theorize that such massive monsters lurk at the hearts of most galaxies. 200-400 billion - Number of stars in the Milky Way. That number is staggering enough. But consider this. Most astronomers say there are at least 100 billion other galaxies out beyond ours. Big as it is, our little corner of the universe really is just that. The Milky Way is but a drop in the bucket.
--Steve Sampson
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