Astronomers Say Milky Way Resides In A Great Cosmic Void.
The Laniakea Supercluster, also called Local Supercluster or Local SCl or sometimes Lenakaeia, is the galaxy supercluster that is home to the Milky Way and approximately 100,000 other nearby galaxies. It was defined in September 2014, when a group of astronomers including R. Brent Tully of the University of Hawaii and Hélène Courtois of the University of Lyon published a new way of defining superclusters according to the relative velocities of galaxies. The new definition of the local supercluster subsumes the prior defined local supercluster, the Virgo Supercluster, now an appendage. The Laniakea Supercluster stretches out about 520 million light-years. It has the approximate mass of 1017 solar masses, or a hundred thousand times that of our galaxy, which is almost the same as that of the Horologium Supercluster. It consists of four subparts, which were known previously as separate superclusters:
- Virgo Supercluster, the part in which the Milky Way resides.
- Hydra-Centaurus Supercluster
- Pavo-Indus Supercluster
- Southern Supercluster, including Fornax Cluster(S373), Dorado and Eridanus clouds.
The entire supercluster consists of approximately 300 to 500 known galaxy clusters and groups. The real number may be much larger because some of these are traversing the Zone of Avoidance, making them essentially undetectable.
Superclusters are some of the universe’s largest structures and have boundaries that are difficult to define, especially from the inside. The team used radio telescopes to map the motions of a large collection of local galaxies. Within a given supercluster, most galaxy motions will be directed inward, toward the center of mass. In the case of Laniakea, this gravitational focal point is called the Great Attractor, and influences the motions of the Local Group of galaxies, where the Milky Way galaxy resides, and all others throughout the supercluster. Unlike its constituent clusters, Laniakea is not gravitationally bound and is projected to be torn apart by dark energy.
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