Milchstraße

Milchstraße is the German name for the Milky Way, the galaxy that contains the Solar System. The term arises from the appearance of a broad, milky band of light spanning the night sky. In scientific usage, the Milky Way is understood as our home galaxy, one of billions in the observable universe.

The Milky Way is a barred spiral galaxy with a diameter of about 100,000 light-years. Its disk is roughly 1,000 light-years thick and hosts hundreds of billions of stars, gas, and dust. The solar system lies in the Orion Arm (a minor spiral arm) about 27,000 light-years from the galactic center. The center contains a supermassive black hole, Sagittarius A*, with a mass of about 4 million solar masses. The galaxy features a central bulge, a central bar, multiple spiral arms, and a halo that includes old stars and globular clusters.

Its structure includes a rotating disk surrounded by a more extended halo. Star formation occurs primarily in the spiral arms and in dense molecular clouds. The Milky Way also harbors vast amounts of gas, dust, and dark matter, which influence its dynamics and evolution. The solar system is part of a local stellar neighborhood within the Local Arm.

The Milky Way is part of the Local Group of galaxies, which is embedded in the larger Virgo–Laniakea supercluster complex. It interacts gravitationally with neighboring galaxies, including the Large and Small Magellanic Clouds, and is expected to collide and merge with the Andromeda Galaxy (M31) in several billion years, forming a larger galaxy. Modern surveys, notably Gaia, map its stars to reveal structure, motion, and the distribution of matter within the Milky Way.