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The galactic plane is the plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms galactic plane and galactic poles usually refer specifically to the plane and poles of the Milky Way, in which Planet Earth is located.
Galactic latitude is positive towards the north galactic pole, with a plane passing through the Sun and parallel to the galactic equator being 0°, whilst the poles are ±90°. [3] Based on this definition, the galactic poles and equator can be found from spherical trigonometry and can be precessed to other epochs; see the table.
The origin essentially coincides with the Earth, because the supergalactic plane is identified as a plane observed from Earth. The north supergalactic pole (SGB = 90°) lies in the constellation Hercules at galactic coordinates (l z = 47.37°, b z = +6.32°), or approximately RA = 18.9 h, Dec = +15.7°.
The galactic coordinate system uses the approximate plane of the Milky Way Galaxy as its fundamental plane. The Solar System is still the center of the coordinate system, and the zero point is defined as the direction towards the Galactic Center. Galactic latitude resembles the elevation above the galactic plane and galactic longitude ...
Quadrants are described using ordinals—for example, "1st galactic quadrant", [1] "second galactic quadrant", [2] or "third quadrant of the Galaxy". [3] Viewing from the north galactic pole with 0 degrees (°) as the ray that runs starting from the Sun and through the galactic center, the quadrants are as follows (where l is galactic longitude):
The result yields a direction perpendicular to the galactic plane. [1] In the case of the Milky Way, this is given by the coordinates of the galactic pole. Galactic clusters [2] [3] are gravitationally bound large-scale structures of multiple galaxies. The evolution of these aggregates is determined by time and manner of formation and the ...
The negative pole is the pole toward which the thumb points when the fingers of the left hand are curled in its direction of rotation. This change was needed because the poles of some asteroids and comets precess rapidly enough for their north and south poles to swap within a few decades using the invariable plane definition.
Yellow plane is celestial equator, P and P' are celestial poles. Green plane is galactic plane, G and G' are galactic poles. B is the direction towards galactic center, which is now used as a starting point for measuring galactic longitude. Prior to 1959, starting point was intersection of galactic and equatorial plane (point C).