Local Group of Galaxies
Local Group of Galaxies
| Group Name | lgrp |
| Reference | Students for the Exploration and Development of Space (SEDS) |
| Prepared by | Brian Abbott (AMNH/Hayden) |
| Labels | Yes |
| Files | localgroup.speck, localgroup.label |
| Dependencies | none |
| Census | 46 galaxies and labels |
The Local Group refers to the few dozen galaxies in our Galactic neighborhood. While these are outside the Milky Way, we include them here to provide a transition to the Extragalactic Atlas portion of the Digital Universe. The group consists of three large spiral galaxies (in order of size): Andromeda, the Milky Way, and M33. The remaining members of the group are dwarf spheroidals, dwarf ellipticals, and irregulars.
The galaxies occupy a space of about 6 million light-years (1 megaparsec) in diameter. The Andromeda Galaxy and the Milky Way dominate, each with a host of small dwarf galaxies huddled around them.
Colliding Galaxies
Several galaxies in our neighborhood are interacting with our Milky Way. Astronomers believe that galaxy interactions and mergers are far more common than once thought. For some time, we have understood the involvement of the Large and Small Magellanic Clouds (LMC and SMC) with our Milky Way. These galaxies are irregular galaxies that are about 160,000 light-years from the center of the Milky Way. Both galaxies contain active star formation as well as older stars and globular clusters. Radio observations also show the possibility of a stream of gas connecting them to the Milky Way.
The LMC was considered to be our nearest neighbor until 1994, when the Sagittarius dwarf elliptical (SgrDEG) was discovered. The SagDEG lies opposite the center of the Milky Way and is interacting with our Galaxy. As it orbits the Milky Way, it is stretched apart, leaving streams of stars in its wake. It's not entirely accurate representing the Sagittarius spheroidal as one point in the Atlas, since these streams are believed to stretch across the Galactic plane over tens of degrees in our sky. The SgrDEG lost the title of closest galaxy in November 2003, when the Canis Major dwarf galaxy was discovered. The Canis Major dwarf is about 25,000 light-years away from the Sun in the constellation Canis Major.
Viewing the Galaxies in the Atlas
Because these points lie so far away, Partiview cannot always handle the enormous scale of these data. Andromeda is, after all, more than 2 million light-years away, far from even the opposite side of the Milky Way. Because we're forcing these data into the parsec scale of the Milky Way Atlas, you may see them flash or they may not be drawn at all.
In order to view these data effectively, you may have to adjust your clipping planes in Partiview. This can be done for the Local Group data with the command
clip 10 1e7shifting the near plane to 10 parsecs and the far plane to 10 million parsecs. This may not work on all systems; the tolerance for these values is heavily dependent on your graphics card and your computer.
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott