Galactic Coordinates Sphere
Galactic Coordinates Sphere
| Group Name | galac |
| Reference | -- |
| Prepared by | Brian Abbott (AMNH/Hayden) |
| Labels | Yes |
| Files | galac.speck |
| Dependencies | none |
Once astronomers understood the structure of our Galaxy in the early part of the 20th century, it was necessary to devise a coordinate system based on that structure. Galactic coordinates are defined by Galactic longitude, l, and Galactic latitude, b, measured in degrees. The “equator” coincides with the plane of the Galaxy. Galactic longitude is measured from Galactic center, which is generally in the direction of Sagittarius A*, a compact radio source that astronomers now know to be about 5 arcminutes from the Galactic nucleus.
The north Galactic pole (b = + 90o) lies in the constellation Coma Berenices, while the south Galactic pole (b = - 90o) is in the constellation Sculptor. These points are perpendicular to the plane of the Galaxy. If you look toward these points in the sky, you are looking directly out of the Galactic plane. Because there are not as many stars or much gas and dust in this direction, we can see objects at greater distances when we look toward the Galactic poles. Other galaxies and clusters of galaxies are easier to find in these regions of the sky.
In the Atlas, we have given the Galactic coordinates a greenish color. Labels appear every 10o in both l and b. The sphere has a radius of 1,000 light-years.
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott