Great Attractor
The Great Attractor is a region of gravitational attraction in
The observed attraction suggests a localized concentration of mass having the order of 1016 solar masses.[1] 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.[2]
The attraction is observable by its effect on the motion of galaxies and their associated clusters over a region of hundreds of millions of
The Great Attractor itself is moving towards the Shapley Supercluster.[2] Recent astronomical studies by a team of South African astrophysicists revealed a supercluster of galaxies, termed the Vela Supercluster, in the Great Attractor's theorized location.[3]
History
The Great Attractor was named by Dressler in 1987[4][5] following decades of redshift surveys that built up 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.[5]: 274
Through a series of peculiar velocity tests, astrophysicists found that the Milky Way was moving in the direction of the
Intense efforts to work through the difficulties caused by the occlusion by the Milky Way during the late 1990's identified the Norma Cluster at the center of the Great Attractor region.[1]
Location
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
Debate over apparent mass
In 1992, much of the apparent signal of the Great Attractor was attributed to a statistical effect called Malmquist bias.[10] In 2005, astronomers conducting an X-ray survey of part of 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 is called the Shapley Attractor.[11]
Laniakea Supercluster
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 is instead anchored by a gravitational focal point. Thus the Great Attractor would be the core of the new supercluster.[12]
See also
- CfA2 Great Wall – Immense galaxy filament
- Dark flow – A possible non-random component of the peculiar velocity of galaxy clusters
- Dark matter – Hypothetical form of matter that interacts with gravity, but not with light or electromagnetic field
- Dipole repeller – Center of effective repulsion in the large-scale flow of galaxies near the Milky Way
- Hercules–Corona Borealis Great Wall – Largest known structure in the observable universe
- Shapley Supercluster – Largest concentration of galaxies in our local universe
- South Pole Wall – Massive cosmic structure
References
- ^ ISBN 978-3-527-40608-1.
- ^ a b "What is the Great Attractor?". Universe Today. 14 July 2014. Retrieved 24 June 2018.
- Wikidata Q55892376.
- ISSN 0036-8733.
- ^ ISSN 0370-1573.
- ^ "Cosmic Microwave Background Dipole | COSMOS". astronomy.swin.edu.au. Retrieved 2022-03-14.
- ^ "Hubble focuses on "the Great Attractor"". NASA. 18 January 2013. Retrieved 24 October 2020.
- S2CID 14507443.
- ^ Mukai, Koji; Mushotzky, Rich; Masetti, Maggie. "The Great Attractor". NASA's Ask an Astrophysicist. Archived from the original on 18 February 2003.
It is now thought that the Great Attractor is probably a supercluster, with Abell 3627 near its center.
- Wikidata Q55968841.
- ^ "X-rays reveal what makes the Milky Way move" (Press release). Ifa.hawaii.edu. 11 January 2006. Retrieved 24 October 2020.
- Wikidata Q28314882.
Further reading
- Dressler, Alan (1994). Voyage to the Great Attractor: Exploring Intergalactic Space. New York, New York: ISBN 978-0-394-58899-5.
- Mathewson D. S.; Ford V. L.; Buchhorn M. (1992). "No back-side infall into the Great Attractor". Letters of the Astrophysical Journal. 389: 5–8. Wikidata Q68868628.
- Wikidata Q68831133.
- Wikidata Q59093661.
- Bertschinger, Edmund; Juszkiewicz, Roman (1988). "Searching for the Great Attractor". The Astrophysical Journal. 334: L59. doi:10.1086/185312.
External links
- Drake, Nadia (3 September 2014). "New map locates Milky Way in neighborhood of 100,000 galaxies". National Geographic. Archived from the original on February 25, 2020.
- Cosmography of the Local Universe. Vimeo (video). – video clip showing the Great Attractor