Laniakea Supercluster

Laniakea Supercluster
Map of galaxies within the nearby universe. Laniakea is the part circled. The arrowed point marked by the Russian "Вы здесь" ("you are here") is the Milky Way.
Observation data (Epoch J2000)
Constellation(s)	Triangulum Australe and Norma (centre)
Right ascension	10h 32m
Declination	−46° 00′ (Great Attractor)
Brightest member	Milky Way (mag –5.0)
Number of clusters	300–500
Major axis	520×10^6 ly (159 Mpc) h−1 0.6780 ± 0.077 (Hubble constant based on Planck data)
Redshift	0.0708 (centre)
Distance (co-moving)	250×10^6 ly (77 Mpc) h−1 0.6780 ± 0.077 (centre) (Hubble constant based on Planck data)
Binding mass	1×1017 M☉
Other designations
Local Supercluster, Laniakea, Laniakea Supercluster, Laniakea Complex
See also: Galaxy groups, Galaxy clusters, List of superclusters

The Laniakea Supercluster (Laniakea; 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 encompasses approximately 100,000 galaxies stretched out over 160 megaparsecs (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:

The most massive galaxy clusters of Laniakea are Virgo, Hydra, Centaurus, Abell 3565, Abell 3574, Abell 3521, Fornax, Eridanus and Norma. 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.