| Laniakea Supercluster | |
|---|---|
.png) A map of the Laniakea and some of its component galaxy superclusters and clusters. Note that other components are missing, such as theGreat Attractor andOphiuchus Cluster. | |
| Observation data (EpochJ2000) | |
| Constellation(s) | Triangulum Australe andNorma (Great Attractor) |
| Right ascension | 10h 32m (Great Attractor)[1] |
| Declination | −46° 00′ (Great Attractor)[1] |
| Number of galaxies | 100,000–150,000 |
| Parent structure | Pisces–Cetus Supercluster Complex[2](Shapley Concentration?)[3][4] |
| Major axis | 404 Mly (124 Mpc)[3]: 3 [a] |
| Redshift | 0.0708 (center) |
| Distance | 250 million ly (77 Mpc)h−1 67.80 ± 0.077 (Great Attractor) (H0 fromPlanck 2013) |
| Binding mass | 1×1017[5] M☉ |
| Other designations | |
| Laniakea, Laniakea Supercluster, Local Supercluster[6][7], Laniakea Complex[8], Laniakea BoA | |
TheLaniakea Supercluster orLaniakea for short (/ˌlɑːni.əˈkeɪ.ə/;Hawaiian for "open skies" or "immense heaven")[9] is thelarge-scale structure centered around theGreat Attractor that is home to theMilky Way and approximately 100,000 other nearby galaxies. It was originally defined in September 2014 as agalaxysupercluster, when a group of astronomers, includingR. Brent Tully of theUniversity of Hawaiʻi at Mānoa,Hélène Courtois of theUniversity of Lyon, Yehuda Hoffman of theHebrew University of Jerusalem, andDaniel Pomarède of CEAUniversité Paris-Saclay published a new way of defining superclusters according to therelative velocities of galaxies as basins of attraction.[5][10] The new definition of theLocal Supercluster[6][7] subsumes the then prior definedVirgo andHydra-Centaurus Supercluster as appendages, the former being the historical local supercluster.[11][8][6][12][7]
Follow-up studies suggest that the Laniakea is not gravitationally bound. It will disperse rather than continue to maintain itself as an overdensity relative to surrounding areas.[13] In addition, some papers favored the traditional definition of superclusters as high-density regions of the cosmic web; basins of attraction including Laniakea were therefore proposed to be called "supercluster cocoons" (or "cocoons" for short), containing smaller traditional superclusters, which evolve inside their parent cocoon.[14]
The Laniakea is the inner part of the localsuperstructure, also known asPisces–Cetus Supercluster Complex.[2] Both are among thelargest known cosmic structures in theobservable universe. Latest observations of basins of attraction suggested abasin of attraction around Ophiuchus Cluster may be associated with Laniakea, and also have found both are moving toward theShapley Concentration and may thus be part of this greater structure.[3][4]
The namelaniākea ([ˈlɐnijaːˈkɛjə]) means 'immense heaven' in Hawaiian], from lani 'heaven' and ākea 'spacious, immeasurable'. The name was suggested byNawaʻa Napoleon, an associate professor of Hawaiian language atKapiʻolani Community College.[15] The name honorsPolynesian navigators, who used knowledge of the sky to navigate the Pacific Ocean.[16]
The Laniakea supercluster encompasses approximately 100,000 galaxies stretched out roughly 120 Mpc (400 million ly).[3] It has the approximate mass of1017solar masses (M☉), or 100,000 times that of our galaxy, which is almost the same as that of theHorologium Supercluster.[5] It consists of several previously defined subparts, including smaller superclusters based on their traditional defintion:
The most massivegalaxy clusters of the Laniakea areVirgo,Hydra,Centaurus,Abell 3565,Abell 3656,Abell 2870,Abell 3581,Abell 3574,Abell 3521,Fornax,Eridanus,Ophiuchus, andNorma. The entire supercluster cocoon consists of approximately 300 to 500 known galaxy clusters and groups.[citation needed] The real number may be much larger because some of these are traversing theZone of Avoidance, an area of the sky that is partially obscured by gas anddust from the Milky Way galaxy, making them essentially undetectable.[citation needed]
Superclusters are some of theuniverse'slargest structures and have boundaries that are difficult to define, especially from the inside. Within a given supercluster, most galaxy motions will be directed inward, toward thecenter of mass. This gravitational focal point, in the case of Laniakea, is called theGreat Attractor, and influences the motions of theLocal Group of galaxies, where the Milky Way galaxy resides, and all others throughout the supercluster. The same study that confirmed the Laniakea proposed to define a supercluster as basins of attraction, rather than high-density regions such as the Virgo Supercluster. Unlike its constituent then-known superclusters, which would collapse in thefar future, Laniakea is, however, notgravitationally bound and is projected to be torn apart bydark energy.[6] Follow-up studies favored the traditional definition of superclusters as high-density regions, with referred to basins of attraction such as Laniakea as "supercluster cocoons" ("cocoons") or "watershed superclusters" ("watersheds").[14][3] Because there is no community consensus on an agreed defintion of the term supercluster, other studies avoid calling any structure a supercluster, including Laniakea andShapley, which were referred as simply basins of attraction.[4]
Although confirmation of the existence of the Laniakea supercluster emerged in 2014,[5] early studies in the 1980s already suggested that several of the then-known superclusters might be connected. For example, South African astronomerTony Fairall stated in 1988 that redshifts suggested that the Virgo and Hydra–Centaurus superclusters may be connected.[18] More recent observations using Cosmicflows-4 catalog have shown that abasin of attraction centered on the Ophiuchus Cluster might be associated with Laniakea, forming a "probabilistic Basin of Attraction" ("p-BoA").[4]
The neighboring superclusters to the Laniakea are theShapley,Hercules,Coma, andPerseus–Pisces Superclusters. The edges of the superclusters and Laniakea were not clearly known at the time of Laniakea's definition.[8] Since then, the study of the edges of superclusters and of structures beyond them has substantially improved.[19][20] Because the Laniakea, Apus, and Coma superclusters are moving toward the Shapley Supercluster, they may be sub-basins part of this larger basin of attraction.[3][4]
Laniakea is also a constituent part of a much larger local superstructure that has also been proposed by R. Brent Tully, referred to as thePisces–Cetus Supercluster Complex, agalaxy filament.[2]
{{cite web}}: CS1 maint: url-status (link)
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.
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| Included | Earth →Solar System →Local Interstellar Cloud →Local Bubble →Gould Belt →Orion Arm →Milky Way →Milky Way subgroup →Local Group→Local Sheet→Local Volume→Virgo Supercluster→Laniakea Supercluster →Pisces–Cetus Supercluster Complex →Local Hole →Observable universe →Universe Each arrow (→) may be read as "within" or "part of". |
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