Local Group
Overview
Galaxy Groups
A group of galaxies is a small number of large galaxies that are typically surrounded by a larger number of small galaxies. These galaxies are gravitationally bound to one another. In the case of the Local Group, there are roughly two substructures, each centered around large, spiral galaxies, with a few other assorted galaxies that interact more loosely with the group.
The Local Group of galaxies. The Milky Way (labeled “Home”) is surrounded by its dwarf galaxies in aqua, the Andromeda Galaxy is surrounded by its dwarfs in yellow, green galaxies are other Local Group members, and gray points are other nearby galaxies. The inner grid extends to one million light years, and the outer grid traces out to ten million light years.
The Milky Way belongs to the Local Group, a term coined by Edwin Hubble (1889–1953), and is one of roughly 100 galaxies in that group. The Milky Way, the Andromeda Galaxy (also known as Messier 31, or M31), and the Triangulum Galaxy (M33) are three of the largest galaxies in the Local Group. Each is a spiral galaxy that contains hundreds of billions of stars.
A close-up of the Milky Way Galaxy and its satellite galaxies in aqua. These include the Large and Small Magellanic Clouds (LMC and SMC, respectively), and some dwarf galaxies only discovered recently because they are interacting with the disk of our Galaxy.
Local Group Colors
The Local Group’s galaxies are given these colors:
Aqua: Galaxies under the gravitational influence of the Milky Way
Yellow: Galaxies in Andromeda’s sphere of influence
Green: Other Local Group members
Gray: Other nearby galaxies
Collisions and Mergers
Surrounding the Milky Way and Andromeda are a bevy of dwarf galaxies—smaller, often irregular galaxies, that contain hundreds of millions to a few billion stars. These dwarf galaxies are typically under the gravitational influence of a larger galaxy, and are often shredded by them at some point over their lifetime. Collisions between galaxies are common, and these smaller galaxies may even be the lifeblood for a larger galaxy by instigating star formation and replenishing its star-forming gas.
As these dwarf galaxies orbit and interact with their parent galaxy, the Milky Way and Andromeda galaxies are heading toward one another. Separated by about 3 million light years, they are moving toward one another at a rate of 120 kilometers per second, or 275,000 miles per hour.
Over the next tens of billions of years, the galaxies of the Local Group will coalesce into one giant elliptical galaxy, driven by the merging of the Milky Way and the Andromeda galaxies.
Looking back toward the Milky Way (aqua) from the Andromeda Galaxy and its dwarf galaxies (yellow). You can see the names of these satellite galaxies often are just numbered versions of Andromeda.
Other Galaxy Groups
The Galaxy Group Labels identify many other nearby galaxy groups. Because the Local Group is, well, local, we see a fairly accurate representation of the dwarf galaxies that inhabit it. Neighboring groups are so far away, it’s difficult to see their smaller members. With these other groups, we really only see the largest, brightest galaxies. If we considered the Local Group from afar, we would probably only see the Milky Way, Andromeda, and M33.
Profiles
Dossier
Census: |
102 galaxies |
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Asset File: |
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OpenSpace Version: |
2 |
Reference: |
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Prepared by: |
Brian Abbott (AMNH) |
Source Version: |
6.04 |
License: |