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16-563: The observed attraction suggests a localized concentration of mass having the order of 10 solar masses. However, it is obscured by the Milky Way's galactic plane , lying behind the Zone of Avoidance (ZOA), so that in visible light wavelengths, the Great Attractor is difficult to observe directly. The attraction is observable by its effect on the motion of galaxies and their associated clusters over

32-420: A large dataset of redshift values. The redshift values and distance measurements independent of redshift measurements were then combined to create maps of peculiar velocity. Through a series of peculiar velocity tests, astrophysicists found that the Milky Way was moving in the direction of the constellation of Centaurus at about 600   km/s. Then, the discovery of cosmic microwave background (CMB) dipoles

48-495: A region of hundreds of millions of light-years across the universe . These galaxies are observable above and below the Zone of Avoidance; all are redshifted in accordance with the Hubble flow , indicating that they are receding relative to the Milky Way and to each other, but the variations in their redshifts are large enough and regular enough to reveal that they are slightly drawn towards

64-469: Is 122.932°. The Galactic Center is located at position angle 31.72° (B1950) or 31.40° (J2000) east of north. Norma Cluster The Norma Cluster ( ACO 3627 or Abell 3627 ) is a rich cluster of galaxies located near the center of the Great Attractor ; it is about 68  Mpc (222  Mly ) distant. Although it is both nearby and bright, it is difficult to observe because it is located in

80-574: Is called the Shapley Attractor . A massive galaxy filament , called the Norma Wall (also called Great Attractor Wall) is located at the center of the supposed position of the Great Attractor. The Norma Wall contains the clusters Pavo II , Norma , Centaurus-Crux and CIZA J1324.7−5736 . The most massive cluster in this region is the Norma supercluster. Later studies found that the wall continues over to

96-491: Is instead anchored by a gravitational focal point. Thus the Great Attractor would be the core of the new supercluster. The local flows of the Laniakea supercluster converge in the region of the Norma and Centaurus Clusters , approximately at the position of the Great Attractor. Galactic plane The galactic plane is the plane on which the majority of a disk-shaped galaxy 's mass lies. The directions perpendicular to

112-457: The Norma Cluster (ACO 3627), a massive cluster of galaxies containing a preponderance of large, old galaxies, many of which are colliding with their neighbours and radiating large amounts of radio waves . In 1992, much of the apparent signal of the Great Attractor was attributed to a statistical effect called Malmquist bias . In 2005, astronomers conducting an X-ray survey of part of

128-477: The attraction. The variations in their redshifts are known as peculiar velocities , and cover a range from about +700 km/s to −700 km/s, depending on the angular deviation from the direction to the Great Attractor. The Great Attractor itself is moving towards the Shapley Supercluster . The Great Attractor was named by Alan Dressler in 1987, following decades of redshift surveys that built up

144-477: The bright star Arcturus ; likewise, the south galactic pole lies in the constellation Sculptor . The zero of longitude of galactic coordinates was also defined in 1959 to be at position angle 123° from the north celestial pole . Thus the zero longitude point on the galactic equator was at 17 42 26.603 , −28° 55′ 00.445″ (B1950) or 17 45 37.224 , −28° 56′ 10.23″ (J2000), and its J2000 position angle

160-400: The constellations of Centaurus and Vela. The proposed Laniakea Supercluster is defined as the Great Attractor's basin. It covers approximately four main galaxy superclusters, including superclusters of Virgo and Hydra–Centaurus , and spans across 500 million light years. Because it is not dense enough to be gravitationally bound, it should be dispersing as the universe expands, but it

176-455: The difficulties caused by the occlusion by the Milky Way during the late 1990s identified the Norma Cluster at the center of the Great Attractor region. The first indications of a deviation from uniform expansion of the universe were reported in 1973 and again in 1978. The location of the Great Attractor was finally determined in 1986: It is situated at a distance of somewhere between 150 and 250 Mly (million light-years) (47–79  Mpc ),

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192-477: The galactic plane point to the galactic poles . In actual usage, the terms galactic plane and galactic poles usually refer specifically to the plane and poles of the Milky Way , in which Planet Earth is located. Some galaxies are irregular and do not have any well-defined disk. Even in the case of a barred spiral galaxy like the Milky Way, defining the galactic plane is slightly imprecise and arbitrary since

208-447: The larger being the most recent estimate, away from the Milky Way , in the direction of the constellations Triangulum Australe (The Southern Triangle) and Norma (The Carpenter's Square). While objects in that direction lie in the Zone of Avoidance (the part of the night sky obscured by the Milky Way galaxy) and are thus difficult to study with visible wavelengths, X-ray observations have revealed that region of space to be dominated by

224-456: The sky known as the Clusters in the Zone of Avoidance (CIZA) project reported that the Great Attractor was actually only one tenth the mass that scientists had originally estimated. The survey also confirmed earlier theories that the Milky Way galaxy is in fact being pulled toward a much more massive cluster of galaxies near the Shapley Supercluster , which lies beyond the Great Attractor, and which

240-524: The stars are not perfectly coplanar . In 1959, the IAU defined the position of the Milky Way's north galactic pole as exactly RA = 12 49 , Dec = 27° 24′ in the then-used B1950 epoch ; in the currently-used J2000 epoch, after precession is taken into account, its position is RA 12 51 26.282 , Dec 27° 07′ 42.01″. This position is in Coma Berenices , near

256-455: Was used to reflect the motion of the Local Group of galaxies towards the Great Attractor. The 1980s brought many discoveries about the Great Attractor, such as the fact that the Milky Way is not the only galaxy impacted. Approximately 400 elliptical galaxies are moving toward the Great Attractor beyond the Zone of Avoidance caused by the Milky Way galaxy light. Intense efforts to work through

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