Local Group
The Local Group is a cluster of galaxies that includes our own Milky Way galaxy. Here's detailed information on this significant astronomical group:
Composition
- The Local Group consists of approximately 54 known galaxies, with the two largest being the Milky Way and the Andromeda Galaxy (M31).
- Other notable members include:
History and Discovery
- The concept of a "Local Group" was first introduced by Edwin Hubble in 1936, when he studied the velocities of nearby galaxies and realized they were moving together as a group.
- Hubble identified 12 galaxies initially, but as technology and observational techniques improved, more galaxies have been added to this group.
Properties
- The Local Group spans about 10 million light-years in diameter.
- It is part of the larger Virgo Supercluster and is moving towards its center.
- The total mass of the Local Group is estimated to be around 1.2 × 10^12 solar masses, dominated by dark matter.
Interactions
- The Milky Way and Andromeda are approaching each other at approximately 100 to 140 kilometers per second and are expected to collide in about 4.5 billion years, potentially merging into one galaxy.
- Smaller galaxies within the group are often tidally stripped by the larger galaxies, leading to interactions like those seen with the Sagittarius Dwarf being consumed by the Milky Way.
Significance in Astronomy
- Studying the Local Group helps astronomers understand galaxy formation, evolution, and the dynamics of galaxy clusters.
- It provides a nearby laboratory for observing phenomena like galaxy mergers, star formation, and the effects of dark matter.
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