Dipole repeller

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Gravitational attraction induces movement towards more dense areas and at the same time the gravitational repulsion pushes the matter back from an empty zone, according to the 'dipole repeller' model. Dipole repeller.svg
Gravitational attraction induces movement towards more dense areas and at the same time the gravitational repulsion pushes the matter back from an empty zone, according to the 'dipole repeller' model.
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The dipole repeller is a center of effective repulsion in the large-scale flow of galaxies in the neighborhood of the Milky Way, first detected in 2017. [1] [2] [3] It is thought to represent a large supervoid, the Dipole Repeller Void. [4]

Contents

The dipole repeller is directly opposed to the Shapley Attractor, an over-density of galaxies located in the Shapley Supercluster. The dipole repeller's apparent repulsion is due to matter in the vicinity being pulled towards the Shapley Attractor, along with the Great Attractor. Due to this, the dipole repeller has likely become devoid of matter, causing an apparent repulsion on galaxies between the repeller and the Shapley Attractor. [5]

Discovery

The Local Group of galaxies is moving relative to the cosmic microwave background (CMB) at 631±20 km/s.

There is also a pattern of bulk flow in the motion of neighboring galaxies extending to distances of over 250 megaparsecs (Mpc). There is a known overdensity – the Shapley Supercluster – creating an attraction in the flow of galaxies.

The repeller appears to be located at a distance of about 220 Mpc and is anticipated to coincide with a void in galaxy density.

That single center of attraction along with a roughly equal single repeller appear to be the most significant contributors to the CMB dipole.

The authors of the article published in Nature Astronomy in January 2017 argue that the distance velocity measurements of the Dipole Repeller are incompatible with an explanation based solely on an attractive gravitational force[ failed verification ]. No single observed concentration of matter (gravitationally attractive) can explain the observed velocities and directions of distance from stars and galaxies. We can therefore observe the presence of an additional force, repulsive and whose nature is not specified, according to these authors.

We show here that repulsion from an underdensity is important and that the dominant influences causing the observed flow are a single attractor — associated with the Shapley concentration — and a single previously unidentified repeller, which contribute roughly equally to the CMB dipole.[...] We conclude that the dipole repeller is not a fictitious structure induced by an ‘edge of the data’ effect, and that subsets of the data, chosen either by distance or galaxy type, uncover a basin of repulsion that ‘pushes’ the Local Group in the direction pointed by the CMB dipole. [6] [ failed verification ]

One of the authors, Hoffman, told The Guardian :

We show that the Shapley attractor is really pulling, but then almost 180 degrees in the other direction is a region devoid of galaxies, and this region is repelling us. So now we have a pull from one side and a push from the other. It’s a story of love and hate, attraction and repulsion, [7]

Hoffman also told Wired :

In addition to being pulled towards the known Shapley Concentration, we are also being pushed away from the newly discovered Dipole Repeller. Thus it has become apparent that push and pull are of comparable importance at our location. [8]

Hoffman told IFLScience:

After subtracting out the mean expansion of the universe, the net gravitational force of the overdense regions is that of an attraction and that of the under-dense regions is that of repulsion. [9]

The CNRS shared the same position and stated in a press release: [10]

Over the years, the debate has bogged down on the relative importance of these two attractors, as they are not enough to explain our movement, especially since it does not point exactly in the direction of Shapley as it should.[...] The team thus discovered that at the location of our galaxy the repulsive and attractive forces from distant entities are of comparable importance and deduced that the major influences that are at the origin of our movement are the Shapley attractor and a vast region of void (i. e. without visible and invisible matter), previously unidentified, that they named the Dipole Repeller. [11]

The same research team identified in September 2017 a second void with repulsive force: the Cold Spot Repeller. [12]

These voids, which repel by the inverse gravitational force, are among main components of the cosmic "V-Web". [13]

Controversy about the Dipole Repeller and its 'repulsive force'

Nevertheless, the discovery of the Dipole Repeller was commented on by astrophysicists and journalists in the mainstream media without using repulsive force [ clarification needed ]. This is the case of Peter Coles, author of the blog "In the dark", [14] Ethan Siegel in an article published by Forbes , [15] as well as in an article published by Ars Technica . [16]

This is because gravitation is an attractive force, but if there is an underdense region it apparently acts as a gravitational repeller, based on the concept that there may be less attraction in the direction of the underdensity, and the greater attraction due to the higher density in other directions acts to pull objects away from the underdensity; in other words, the apparent repulsion is not an active force, but due simply to the lack of a force counteracting the attraction. [17]

See also

Related Research Articles

<span class="mw-page-title-main">Supercluster</span> Large group of smaller galaxy clusters or galaxy groups

A supercluster is a large group of smaller galaxy clusters or galaxy groups; they are among the largest known structures in the universe. The Milky Way is part of the Local Group galaxy group, which in turn is part of the Virgo Supercluster, which is part of the Laniakea Supercluster. The large size and low density of superclusters means that they, unlike clusters, expand with the Hubble expansion. The number of superclusters in the observable universe is estimated to be 10 million.

The following is a timeline of galaxies, clusters of galaxies, and large-scale structure of the universe.

<span class="mw-page-title-main">Virgo Supercluster</span> Galactic supercluster containing the Virgo Cluster

The Virgo Supercluster or the Local Supercluster is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs. The Virgo SC is one of about 10 million superclusters in the observable universe and is in the Pisces–Cetus Supercluster Complex, a galaxy filament.

<span class="mw-page-title-main">Great Attractor</span> Apparent gravitational anomaly in the local supercluster

The Great Attractor is a purported gravitational attraction in intergalactic space and the apparent central gravitational point of the Laniakea Supercluster of galaxies. This supercluster contains the Milky Way galaxy, as well as about 100,000 other galaxies.

Richard Brent Tully is a Canadian-born American astronomer at the Institute for Astronomy in Honolulu, Hawaii.

<span class="mw-page-title-main">Hydra–Centaurus Supercluster</span> Closest neighboring galaxy supercluster

The Hydra–Centaurus Supercluster, or the Hydra and Centaurus Superclusters, is a supercluster in two parts, the closest neighbour of Virgo Supercluster. It is located about 39 Mpc (127 Mly) away.

The Shapley Supercluster or Shapley Concentration is the largest concentration of galaxies in our nearby universe that forms a gravitationally interacting unit, thereby pulling itself together instead of expanding with the universe. It appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus. It is 650 million light-years away (z=0.046).

<span class="mw-page-title-main">Pavo–Indus Supercluster</span> Neighboring supercluster in the constellations Pavo,Indus and Telescopium

The Pavo–Indus Supercluster is a neighboring supercluster located about 60–70 Mpc (196–228 Mly) away in the constellations of Pavo, Indus, and Telescopium. The supercluster contains three main clusters, Abell 3656, Abell 3698, and Abell 3742.

<span class="mw-page-title-main">Galaxy filament</span> Largest structures in the universe, made of galaxies

In cosmology, galaxy filaments are the largest known structures in the universe, consisting of walls of galactic superclusters. These massive, thread-like formations can commonly reach 50/h to 80/h Megaparsecs — with the largest found to date being the Hercules-Corona Borealis Great Wall at around 3 gigaparsecs (9.8 Gly) in length — and form the boundaries between voids. Due to the accelerating expansion of the universe, the individual clusters of gravitationally bound galaxies that make up galaxy filaments are moving away from each other at an accelerated rate; in the far future they will dissolve.

The Pisces–Cetus Supercluster Complex is a galaxy filament. It includes the Laniakea Supercluster which contains the Virgo Supercluster lobe which in turn contains the Local Group, the galaxy cluster that includes the Milky Way. This filament is adjacent to the Perseus–Pegasus Filament.

<span class="mw-page-title-main">Local Sheet</span> Nearby extragalactic region of space

The Local Sheet in astronomy is a nearby extragalactic region of space where the Milky Way, the members of the Local Group and other galaxies share a similar peculiar velocity. This region lies within a radius of about 7 Mpc (23 Mly), 0.46 Mpc (1.5 Mly) thick, and galaxies beyond that distance show markedly different velocities. The Local Group has only a relatively small peculiar velocity of 66 km⋅s−1 with respect to the Local Sheet. Typical velocity dispersion of galaxies is only 40 km⋅s−1 in the radial direction. Nearly all nearby bright galaxies belong to the Local Sheet. The Local Sheet is part of the Local Volume and is in the Virgo Supercluster. The Local Sheet forms a wall of galaxies delineating one boundary of the Local Void.

<span class="mw-page-title-main">Laniakea Supercluster</span> Galaxy supercluster that is home to the Milky Way Galaxy and many more galaxies

The Laniakea Supercluster is the galaxy supercluster that is home to the Milky Way and approximately 100,000 other nearby galaxies.

The Taurus Void is a vast, near-empty region of space situated between the Perseus–Pisces Supercluster and the Virgo Supercluster. The Taurus void is unique because of its relatively close proximity to Earth, and because it helps to define the edge of latter's home supercluster, the Virgo Supercluster. Despite its close proximity to Earth, the Taurus Void is not well-studied because it is partially obscured by the Milky Way when viewed from Earth. In contrast to its ambiguous boundary in the section of sky obscured by the Milky Way, the Taurus Void has a very well-defined boundary with the Perseus-Pisces supercluster.

The Shapley attractor is an attractor located about the Shapley Supercluster.

<span class="mw-page-title-main">Southern Supercluster</span> Closest neighboring galaxy supercluster

The Southern Supercluster is a nearby supercluster located around 19.5 Mpc (63.6 Mly) in the constellations of Cetus, Fornax, Eridanus, Horologium, and Dorado. It was first identified in 1953 by Gérard de Vaucouleurs.

<span class="mw-page-title-main">Hélène Courtois</span> French astrophysicist

Hélène Courtois is a French astrophysicist specialising in cosmography. She is a professor at the University of Lyon 1 and has been a chevalier of the Ordre des Palmes Académiques since 2015.

Daniel Pomarède is a staff scientist at the Institute of Research into the Fundamental Laws of the Universe, CEA Paris-Saclay University. He co-discovered Laniakea, our home supercluster of galaxies, and Ho'oleilana, a spherical shell-like structure 1 billion light-years in diameter found in the distribution of galaxies, possibly the remnant of a Baryon Acoustic Oscillation. Specialized in data visualization and cosmography, a branch of cosmology dedicated to mapping the Universe, he also co-authored the discoveries of the Dipole Repeller and of the Cold Spot Repeller, two large influential cosmic voids, and the discovery of the South Pole Wall, a large-scale structure located in the direction of the south celestial pole beyond the southern frontiers of Laniakea.

<span class="mw-page-title-main">South Pole Wall</span> Massive cosmic structure

The South Pole Wall is a massive cosmic structure formed by a giant wall of galaxies that extends across at least 1.37 billion light-years of space, the nearest light of which is aged about half a billion light-years. The structure, in its astronomical angle, is dense in five known places including one very near to the celestial South Pole and is, according to the international team of astronomers that discovered the South Pole Wall, "...the largest contiguous feature in the local volume and comparable to the Sloan Great Wall at half the distance ...". Its discovery was announced by Daniel Pomarède of Paris-Saclay University and R. Brent Tully and colleagues of the University of Hawaiʻi in July 2020. Pomarède explained, "One might wonder how such a large and not-so distant structure remained unnoticed. This is due to its location in a region of the sky that has not been completely surveyed, and where direct observations are hindered by foreground patches of galactic dust and clouds. We have found it thanks to its gravitational influence, imprinted in the velocities of a sample of galaxies".

The Telescopium−Grus Cloud is a galaxy filament in the constellations of Pavo, Indus, and Telescopium. It was first defined by astronomer Brent Tully in his book The Nearby Galaxies Atlas and its companion book The Nearby Galaxies Catalog.

The Southern Supercluster Strand is a galaxy filament that incompasses the Southern Supercluster and the Telescopium−Grus Cloud.

References

  1. ↑ Hoffman, Yehuda; Pomarède, Daniel; Tully, R. Brent; Courtois, Hélène M. (30 January 2017). "The dipole repeller". Nature Astronomy. 1 (2): 0036. arXiv: 1702.02483 . Bibcode:2017NatAs...1E..36H. doi:10.1038/s41550-016-0036. S2CID   7537393.
  2. ↑ Strickland, Ashley (31 January 2017). "Milky Way galaxy is being pushed across the universe". CNN. Retrieved 29 July 2017.
  3. ↑ Woollaston, Victoria. "The Milky Way is being pushed through space by a void called the Dipole Repeller". WIRED UK. Retrieved 2017-02-01.
  4. ↑ Carlisle, Camille M. (2017-01-30). "Cosmic Void "Pushes" Milky Way". Sky & Telescope. Retrieved 2019-01-31.
  5. ↑ Sample, Ian (2017-01-30). "Milky Way being pushed through space by cosmic dead zone, say scientists". The Guardian. ISSN   0261-3077 . Retrieved 2019-01-05.
  6. ↑ Courtois, Hélène M.; Tully, R. Brent; Pomarède, Daniel; Hoffman, Yehuda (February 2017). "The dipole repeller". Nature Astronomy. 1 (2): 0036. arXiv: 1702.02483 . Bibcode:2017NatAs...1E..36H. doi:10.1038/s41550-016-0036. ISSN   2397-3366. S2CID   7537393.
  7. ↑ Sample, Ian (2017-01-30). "Milky Way being pushed through space by cosmic dead zone, say scientists". The Guardian. ISSN   0261-3077 . Retrieved 2019-01-05.
  8. ↑ Woollaston, Victoria (2017-01-30). "The Milky Way is being pushed through space by a void called the Dipole Repeller". Wired UK. ISSN   1357-0978 . Retrieved 2019-01-05.
  9. ↑ "The Milky Way Is Running Away From An Extragalactic Void". IFLScience. 30 January 2017. Retrieved 2019-01-05.
  10. ↑ "Poussée par un vide, notre galaxie surfe à plus de 2 millions de km/h" (PDF). cnrs.fr (in French). 30 January 2017. Retrieved 2019-01-05.
  11. ↑ "Au fil des ans, le débat s’est enlisé sur l'importance relative de ces deux attracteurs, ceux-ci ne suffisant pas pour expliquer notre mouvement, d’autant qu’il ne pointe pas exactement dans la direction de Shapley comme cela devrait être le cas. [...] L’équipe a ainsi découvert qu’à l’emplacement de notre galaxie les forces répulsives et attractives provenant d’entités lointaines sont d'importances comparables et en a déduit que les influences majeures qui sont à l’origine de notre mouvement sont l'attracteur Shapley et une vaste région de vide (c’est-à-dire dépourvue de matière visible et invisible), précédemment non identifiée, qu’ils ont nommé le Dipole Repeller."
  12. ↑ Courtois, Hélène M.; Tully, R. Brent; Hoffman, Yehuda; Pomarède, Daniel (2017). "Cosmicflows-3: Cold Spot Repeller?". The Astrophysical Journal Letters. 847 (1): L6. arXiv: 1708.07547 . Bibcode:2017ApJ...847L...6C. doi: 10.3847/2041-8213/aa88b2 . ISSN   2041-8205.
  13. ↑ Pomarède, Daniel; Hoffman, Yehuda; Courtois, Hélène M.; Tully, R. Brent (August 2017). "The Cosmic V-Web". The Astrophysical Journal. 845 (1): 55. arXiv: 1706.03413 . Bibcode:2017ApJ...845...55P. doi: 10.3847/1538-4357/aa7f78 . ISSN   0004-637X.
  14. ↑ "The Dipole Repeller". In the Dark. 2017-02-02. Retrieved 2019-01-05.
  15. ↑ Siegel, Ethan (4 Feb 2017). "Ask Ethan: If Gravity Attracts, How Can The 'Dipole Repeller' Push The Milky Way?". Forbes Magazine. Retrieved 2019-01-05.
  16. ↑ Rzetelny, Xaq (2017-02-03). "Milky Way is not only being pulled—it's also "pushed" by a void". Ars Technica. Retrieved 2019-01-05.
  17. ↑ Piran, Tsvi (1997-11-01). "On Gravitational Repulsion". General Relativity and Gravitation. 29 (11): 1363–1370. arXiv: gr-qc/9706049 . Bibcode:1997GReGr..29.1363P. doi:10.1023/A:1018877928270. ISSN   1572-9532. S2CID   9458336.
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