The Laniakea Supercluster (Laniakea, Hawaiian for open skies or immense heaven; 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, Hélène Courtois of the University of Lyon, Yehuda Hoffman
of the Hebrew University of Jerusalem, and Daniel Pomarède of CEA Université Paris-Saclay
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, as an appendage.Follow-up studies suggest that Laniakea is not gravitationally
bound; it will disperse rather than continue to maintain itself as an overdensity relative
to surrounding areas.
== Name == The name laniakea means 'immense heaven' in
Hawaiian, from lani, meaning 'heaven', and ākea, meaning 'spacious, immeasurable'.
The name was suggested by Nawa'a Napoleon, an associate professor of Hawaiian language
at Kapiolani Community College.
The name honors Polynesian navigators, who used knowledge of the heavens to navigate
the Pacific Ocean.
== Characteristics == 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:
Virgo Supercluster, the part in which the Milky Way resides.
Hydra-Centaurus Supercluster the Great Attractor, Laniakea's central gravitational
point near Norma Antlia Wall, known as Hydra Supercluster
Centaurus Supercluster Pavo-Indus Supercluster
Southern Supercluster, including Fornax Cluster (S373), Dorado and Eridanus cloudsThe 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.
== Discovery method == The new method used to analyze galaxy movements
to distinguish peculiar motion from cosmic expansion is Wiener filtering, which works
for well-defined positional information, allowing analysis out to about 300×10^6 ly (92 Mpc),
showing flow patterns.
With that limitation, Laniakea is shown to be heading in the direction of the Shapley
Supercluster.South African astronomer Tony Fairall stated in 1988 that redshifts suggested
that the Virgo and Hydra-Centaurus Superclusters may be connected.
== Location == The neighboring superclusters to Laniakea
are the Shapley Supercluster, Hercules Supercluster, Coma Supercluster and Perseus-Pisces Supercluster,
they are all part of the composition of the Pisces-Cetus Supercluster Complex.
The edges of the superclusters and Laniakea were not clearly known at the time of Laniakea's
definition.
== See also