Milky Way

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Milky Waysearch for term: Our galaxy.

The Milky Way is a spiral, or disk-shaped, galaxy with four major arms containing young bright stars, gas, and dust. From the Earth, the Milky Way is seen edge-on as a swath of patchy white glow in the sky. The mass of the entire Milky Way is estimated to be between 400 billion and one trillion solar masses, and the luminous diameter of the Galaxy is some 80,000 light-years across. The entire Solar System orbits the center of the Milky Way once every 200 million years at a distance of 25,000 light-years from the Galactic center, which is located in the direction of the constellation Sagittarius. Sometimes, astronomers refer to the Milky Way as the Galaxy.