Other meanings of Galactic plane
Astronomy
The Galactic plane is the plane in which most of the Milky Way’s mass, stars, and interstellar matter lie. It is the midplane of the Galactic disk, a flattened system of stars, gas, and dust that rotates around the Galactic Center. The plane is inclined at about 60° to the ecliptic, and its projection on the sky forms the bright band of the Milky Way, which is visible to the naked eye as a hazy band of light. The Sun lies close to the plane, about 26,000 light-years from the Galactic Center, and its position defines the plane's orientation in space.
The Galactic plane is the fundamental reference plane of the Milky Way's disk, defined by the mean distribution of its stars and interstellar matter. It is the plane of symmetry of the Galactic disk, which is a flattened, rotating structure with a scale height of only about 1,000 light-years for the thin disk, compared to a diameter of roughly 100,000 light-years. The plane is inclined at about 60° to the ecliptic, and its north pole lies in the constellation Coma Berenices. The Sun is located close to the plane, about 26,000 light-years from the Galactic Center, and its position defines the plane's orientation in space.
The projection of the Galactic plane onto the celestial sphere is the Milky Way band, a bright, irregular band of light that encircles the sky. This band is the integrated light of countless stars and nebulae concentrated in the plane, and it is most prominent in the constellations Sagittarius, Scorpius, and Cygnus. The plane is also the locus of most interstellar dust, which obscures visible light and creates dark rifts, such as the Great Rift in Cygnus. Observations in radio and infrared wavelengths, which penetrate dust, reveal the plane's structure, including spiral arms and giant molecular clouds, and are essential for mapping the Galaxy's spiral structure.
In the Galactic coordinate system, the Galactic plane serves as the fundamental plane, with Galactic latitude (b) measured perpendicular to it and Galactic longitude (l) measured along it. The zero point of longitude is the direction of the Galactic Center, which lies in Sagittarius. This system is used to map the distribution of stars, gas, and dust in the Milky Way. The plane is also the reference for studies of the Galaxy's warp and flare, which are deviations from a perfectly flat disk. The warp, a bending of the outer disk, is particularly evident in the distribution of neutral hydrogen, and the flare, an increase in thickness with radius, is seen in stellar populations.
The Galactic plane is not perfectly flat; it exhibits a warp and a flare, which are likely caused by tidal interactions with satellite galaxies, such as the Magellanic Clouds. The plane also contains a thin layer of diffuse ionized gas, known as the Reynolds layer, which is traced by radio recombination lines. The Sun's position is slightly above the plane (about 20 light-years north), and it oscillates through the plane with a period of about 60 million years, which may influence the Earth's climate and impact cratering rates. The plane is also the site of most of the Galaxy's star formation, with giant molecular clouds and H II regions concentrated along it. In addition, the plane is the source of a diffuse gamma-ray emission, which is produced by cosmic-ray interactions with interstellar gas and radiation fields.
The Galactic plane is a fundamental reference for understanding the structure and evolution of the Milky Way.
Help improve the encyclopedia. Reports go straight to the site manager.