The Galactic Halo
The Galactic Halo
| Group Name | halo |
| Reference | Merrifield, M. & Binney, J. 1998, Galactic Astronomy (Princeton: Princeton University Press) |
| Prepared by | Brian Abbott (AMNH/Hayden) |
| Labels | No |
| Files | halo.speck |
| Dependencies | none |
Surrounding the disk of the Milky Way is the spherical Galactic halo. Unlike the population of the disk, where stars continue to form, the halo population is devoid of gas and dust and, therefore, star formation. It contains cooler, dimmer stars left over from an era of star formation in the Galaxy's early history. There are no young, luminous stars in this population.
The main player in the Galactic halo is the system of globular clusters. Numbering about 150, the Milky Way's globulars are spherically distributed about the Galactic center, and most are within the halo. The stars in the halo are so intrinsically dim that it is difficult to see them unless they are very close to the Sun. These stars travel in elliptical orbits about the center of the Galaxy that are not confined to the disk but are distributed throughout the spherical halo.
Many properties of the halo are still under consideration by astronomers. With the introduction of dark matter and the discovery of more small satellite galaxies around the Milky Way, the halo seems to come under continual scrutiny. We place the radius of the halo at about 134,000 light-years (41 kpc); however, some astronomers believe it to be far larger, perhaps as much as 300,000 to 800,000 light-years in radius.
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott