Galactic plane

The midplane of the Milky Way’s disk, where most of its stars, gas, and dust are concentrated. It defines the disk’s principal orientation in the sky.

Milky Way: The barred spiral galaxy that contains the Sun and billions of other stars. Its disk supplies the large-scale structure whose central plane is the galactic plane.
Angular momentum: A conserved physical quantity that measures rotational motion. The disk’s shared angular momentum helps explain why much of its matter settles into a plane.
Galactic latitude: The angular distance of a sky position north or south of the galactic plane. It measures how far a sightline lies from the plane.
Ecliptic: The apparent annual path of the Sun across the celestial sphere, corresponding to Earth’s orbital plane. Earth’s orbital plane is tilted relative to the Milky Way’s disk plane.
Galactic disk: The flattened component of a galaxy containing stars, gas, and dust in orbit around its center. The galactic plane is the central midplane of the Milky Way’s disk.
Galactic rotation: The orbital motion of stars and gas around a galaxy’s center. Rotation organizes much of the Milky Way’s disk around the plane.
Galactic longitude: The angular position of a sky location measured around the galactic plane from the Galactic center. It locates objects along the plane’s direction on the sky.
Celestial equator: The projection of Earth’s equator onto the celestial sphere. It is an Earth-based reference plane, not the Milky Way’s disk midplane.
Galactic bulge: The dense, roughly spheroidal concentration of stars surrounding the Milky Way’s center. Its central position anchors the inner end of the disk’s plane.
Molecular cloud: A cold, dense interstellar cloud composed mainly of molecular hydrogen. Many molecular clouds occupy the plane, where new stars form.

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Messier 7Related: Messier 7 appears close to the Milky Way’s crowded central band.