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.
Map of the Laniakea Supercluster and its component galaxy clusters
|Observation data (Epoch J2000)|
|Constellation(s)||Triangulum Australe and Norma (centre)|
|Right ascension||10h 32m|
|Brightest member||Milky Way (mag –5.0)|
|Number of clusters||300–500|
|Major axis||520×106 ly (159 Mpc) h−1|
0.6780 ± 0.077
(Hubble constant based on Planck data)
|250×106 ly (77 Mpc) h−1|
0.6780 ± 0.077 (centre)
(Hubble constant based on Planck data)
|Binding mass||1×1017 M☉|
|Local Supercluster, Laniakea, Laniakea Supercluster, Laniakea Complex|
|See also: Galaxy groups, Galaxy clusters, List of superclusters|
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.
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
- Pavo-Indus Supercluster
- Southern Supercluster, including Fornax Cluster (S373), Dorado and Eridanus clouds
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.
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 300×106 ly (92 Mpc), showing flow patterns. With that limitation, Laniakea is shown to be heading in the direction of the Shapley Supercluster, so both Shapley and Laniakea may be part of the Pisces-Cetus Supercluster complex .
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.
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.
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- Chon, Gayoung; Böhringer, Hans; Zaroubi, Saleem (2015). "On the definition of superclusters". Astronomy & Astrophysics. 575: L14. arXiv:1502.04584. Bibcode:2015A&A...575L..14C. doi:10.1051/0004-6361/201425591.
- Camille M. Carlisle (3 September 2014). "Laniakea: Our Home Supercluster". Sky and Telescope.
- Fairall, Anthony Patrick (1988). "A redshift map of the Triangulum Australe-Ara region – Further indication that Centaurus and Pavo are one and the same supercluster". Monthly Notices of the Royal Astronomical Society. 230 (1): 69–77. Bibcode:1988MNRAS.230...69F. doi:10.1093/mnras/230.1.69.
- R. Brent Tully; Hélène Courtois; Yehuda Hoffman; Daniel Pomarède (2 September 2014). "The Laniakea supercluster of galaxies". Nature (published 4 September 2014). 513 (7516): 71. arXiv:1409.0880. Bibcode:2014Natur.513...71T. doi:10.1038/nature13674. PMID 25186900.
- Meet Laniakea, Our Home Supercluster
|Wikiquote has quotations related to: Laniakea Supercluster|
- Vimeo, "Laniakea Supercluster", Daniel Pomarède, 4 September 2014—video representation of the findings of the discovery paper
- YouTube, "Laniakea: Our Home Supercluster", Nature Video, 3 September 2014—Redrawing the boundaries of the cosmic map, they redefine our home supercluster and name it Laniakea.