Earth’s Galaxy: The Milky Way

Earth's Galaxy: The Milky Way

Milky Way ArmsThe word galaxy is derived from the Greek word meaning “milky” and is used to describe a large island of stars in space which are held together by their mutual gravity and dark matter. Our solar system forms an extremely tiny part of a spiral galaxy called the Milky Way, which is made up of an estimated 100 billion stars, including our own sun.

The Milky Way presents an incredible site for stargazers everywhere and appears as a long line of stars in the night sky but heavily concentrated in the middle, almost as if you were looking at a fried egg side on. All the stars we see are inside our own galaxy, and there are billions of other galaxies like our own in the Universe.

The core of the Milky Way contains all the older stars surrounded by a nursery of young stars. The Milky Way is about 100,000 light years across and the further you travel out from the centre the older the stars then become. Our sun is quite old and found three-quarters the way out towards the edge of our galaxy, roughly 28,000 light years from its center.

Spiral Galaxy The Milky Way Galaxy is spinning, and our solar system completely orbits the galaxy once every 225 million years. The Milky Way galaxy (click picture to enlarge) has four major arms stretching out from its centre, with minor arms extending out from them. The Sun is located between the Sagittarius Arm and the Perseus Arm of the Milky Way, in a minor area called the Orion spiral arm, so named for its proximity to the stars in the Orion constellation. There is speculation that the minor Orion Arm, which includes our solar system and Earth, is a branch of the Perseus Arm, but this is unconfirmed.

Next: Constellations and Mythology


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