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The Universe consists of billions of galaxies; we and our star, the Sun, belong to the Milky Way Galaxy. While there are different shapes of galaxies, the most common shape is the disc. Typically a galaxy consists of a few hundred billion stars, most of the being fly-weight and light-weight start. Because of the enormous distances between objects in space, units such as miles and kilometers are of no value. Instead, the astronomers use one of two units of distance measurement, the light year(LY) and the parsec (pc) as their units of measurement. One light year equals 6 X 1012 miles while one parsec equals 3.3 light years. Of the two, the light year is the most commonly used. Or galaxy is 100,000 LY across and 20,000 LY along the rotational axis. It rotates about once every 250,000 years. The highest density of stars is located at the center of the galaxy, decreasing toward the outer extremes. Our star, the Sun is located about 50,000 LY from the center. Located near the edge where few stars exist, we can see beyond our galaxy to distant galaxies, the nearest of which is Andromeda at a distance of 2.5 LY. Our nearest neighbor, the star Alpha Centauri is only 4 LY away.


Milky Way, galaxy