The strip of light that appears in the center of the photo and crosses the sky is a small part of our galaxy, the Milky Way. It is easily recognizable to the naked eye on clear nights. Sometimes a full arch can be seen in the night sky.
Oddly enough, being so large and not having an image of it from the outside, it is harder to study than other distant galaxies. The complete image that astronomers have created of the Milky Way is just the sum of the various partial observations.
The Milky Way is a barred spiral-shaped galaxy, like a grinder. Its width is between 100,000 and 120,000 light years. It is formed by more than 200,000 million stars. All the stars we see with the naked eye belong to her. Only a few faint spots of the sky remain outside the Milky Way: the Magellanic Clouds in the southern sky, and Andromeda, the furthest object visible to the naked eye and observable from both hemispheres.
At its core are the oldest, red and yellow stars. Four arms extend around it: Centaur Cross Arm, Sagittarius Arm, Orion Arm and Perseus Arm. The youngest stars form on the Arms and are white or blue. From the data that the Hubble telescope collects from other galaxies, it is believed that there could be a black hole in the center of the Milky Way.
The Solar System is located in the Orion Arm, 30,000 light years from the center of the galaxy. It takes 225 million years to make a complete turn.
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