Galactic Quadrant

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Longitudes of the galactic coordinate system .

A galactic quadrant or quadrant of a galaxy denotes one of four sectors of a circle as the division of the Milky Way .

Quadrants in the galactic coordinate system

In astronomical practice, the galactic quadrants in the galactic coordinate system are set by the sun as the pole (instead of the galactic center for practical reasons ), since all astronomical observations (from humans ) to this day proceed from the earth or the solar system .

Demarcation

Quadrants are denoted by ordinal numbers , for example "1st galactic quadrant", "second galactic quadrant" or "third quadrant of the galaxy". When viewed from the north, the galactic poles result from 0 degrees (°) as a ray that runs from the sun and through the galactic center. Then the quadrants are determined as follows:

  • 1st galactic quadrant - 0 ° ≤ longitude (ℓ) ≤ 90 °
  • 2nd galactic quadrant - 90 ° ≤ ℓ ≤ 180 °
  • 3rd galactic quadrant - 180 ° ≤ ℓ ≤ 270 °
  • 4th Galactic Quadrant - 270 ° ≤ ℓ ≤ 360 ° (0 °)

visibility

Alignment of the galaxy, the ecliptic and the equatorial coordinate system , each projected onto the celestial sphere .

Due to the orientation of the earth in relation to the rest of the galaxy , the second galactic quadrant is primarily visible from the northern hemisphere , while the fourth is mostly only visible from the southern hemisphere . Therefore, the division into quadrants is usually more practical for amateur astronomers, but international astronomical organizations are not bound to the earth's horizon .

From the earth you can recognize the boundaries of the quadrants using the following main constellations (as a rough orientation):

  • You look to 0 ° when you look in the direction of the constellation Sagittarius .
  • You look to 90 ° if you look in the direction of the constellation Swan .
  • You look to 180 ° when you look in the direction of the constellation Fuhrmann .
  • You look to 270 ° when you look in the direction of the constellation Sails of the Ship .

Science fiction

In Star Trek , a galactic quadrant is defined as a sector of a circle, which has the galactic center as a pole and makes up exactly 1/4 of the area of ​​the galactic disk. The clockwise quadrants are named Alpha, Gamma, Delta and Beta. The solar system lies exactly on the border between the alpha and beta quadrant.

Web links

Individual evidence

  1. ↑ Michael Okuda , Denise Okuda, Debbie Mirek: STAR TREK The official encyclopedia. HEEL-Verlag, 1995, ISBN 3-89365-449-6 .