Hercules–Corona Borealis Great Wall

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Hercules–Corona Borealis Great Wall
Hubble image of MACS J0717 with mass overlay.jpg
A giant Hubble mosaic of the massive galaxy cluster MACS J0717.5+3745 using a combination of 18 images. The significant amount of dark matter in this cluster, shown in light blue, may be also similar to the Hercules–Corona Borealis Great Wall.
Credit: Hubble Space Telescope
Observation data (Epoch J2000)
Constellation(s) Hercules and Corona Borealis[1]
Right ascension 17h 50m
Declination +27° 45′
Major axis Gpc (10 Gly)[1][2]
Minor axis 2.2 Gpc (7 Gly) h−1
0.6780
Redshift 1.6 to 2.1[1][2]
Distance
(co-moving)
9.612 to 10.538 billion light-years (light travel distance)[3]
15.049 to 17.675 billion light-years
(present comoving distance)[3]
Binding mass 1.5×1019 M[citation needed]
See also: Galaxy groups, Galaxy clusters, List of superclusters

The Hercules–Corona Borealis Great Wall (Her–CrB GW) is an immense superstructure of galaxies that measures more than 10 billion light-years across.[1][2] It is the largest and the most massive structure known in the observable universe.

This huge structure was discovered in November 2013 by a mapping of gamma-ray bursts that occur in the distant universe.[1][2][4] The astronomers used data from the Swift Gamma-Ray Burst Mission, Fermi Gamma-ray Space Telescope, Compton Gamma Ray Observatory, and the BeppoSAX and INTEGRAL satellites.[5]

The Hercules–Corona Borealis Great Wall was also the first structure other than large quasar groups that held the title as largest known structure in the universe, since 1991.

Characteristics[edit]

The structure is a galaxy filament,[2] or a huge group of galaxies assembled by gravity. It is about 10 billion light-years (3 Gpc) at its longest dimension, which is approximately 1/9 (10.7%) of the diameter of the observable universe, 7.2 billion light-years (2.2 Gpc; 150,000 km/s in redshift space) wide,[2] but only 900 million light-years (300 Mpc) thick, and is the largest known structure in the universe. It is at redshift 1.6–2.1, corresponding to a distance of approximately 10 billion light-years away,[1][2] and is located in the sky in the direction of the constellations Hercules and Corona Borealis.[4]

Discovery[edit]

Swift Satellite
Fermi Gamma-Ray Satellite
Compton Gamma Ray Observatory
BeppoSAX
Top to bottom: The Swift Satellite, Fermi Gamma-ray Space Telescope, Compton Gamma Ray Observatory, BeppoSAX, and INTEGRAL (not shown), collected data that helped to trace the Hercules–Corona Borealis Great Wall.
Artist's impression of a powerful gamma-ray burst. Through extrapolating and correlating these events, the Hercules–Corona Borealis Great Wall is traced.

Gamma-ray bursts (GRBs) are some of the most powerful events in the known universe. They are very luminous flashes of gamma rays heralding the death of distant, massive stars in cataclysmic explosions. Gamma-ray bursts are rare; only one happens in an average galaxy like the Milky Way every few million years. Since it is currently theorized that the stars causing these events are the massive, luminous ones, such stars form in regions with more matter in general. Therefore, gamma-ray bursts can be indicators of galaxies to track down traces of matter decoupling in such a region of the universe.

Using the observed data from 1997 to 2012[1][2][6] taken by Istvan Horvath and Zsolt Bagoly of the National University of Public Service in Budapest, Hungary and Jon Hakkila of the College of Charleston in South Carolina, United States, from some of the world's most sophisticated and most advanced gamma-ray telescopes, the sky was subdivided into 9 parts with 31 GRBs each. In the data for one of the subdivisions, using the two-dimensional Kolmogorov–Smirnov test, 14 out of the 31 GRBs are concentrated in a radial area that is 45° wide, with redshifts from 1.6 to 2.1; if many GRBs occur in a region, it must be a decoupling of thousands—or possibly millions—of galaxies.

The team also found out that the probability to find a similar clustering was less than 0.00055%,[2] rendering its existence due to quantum fluctuations in the early universe very unlikely to almost impossible in the standard Gaussian statistics. So the structure's existence under the accepted cosmological models was not only doubtful, but very impossible.

Scale[edit]

To help the reader comprehend the massive scale of this object, this structure is 10 billion light-years across, or equivalent to 9.46 × 1025 kilometres. If the Sun, with the diameter of 1,392,000 kilometres, were only as big as a ping-pong ball, the next nearest star, Proxima Centauri, would be a pea 1,152 kilometres away; the Milky Way would be about 30 million kilometres wide, about a fifth of the distance of the Earth from the Sun, and the Her–CrB GW would be about 3 trillion kilometres long, about four light-months, and Voyager 1, the fastest known man-made object, will take 4,800 years to travel that distance, assuming its current speed of 17 km/sec will not change. At this scale, the Earth would be smaller than a drop of dew.

The extreme scale of this structure poses some interesting problems to astronomers. These problems are discussed below.

Homogeneity problem[edit]

According to the cosmological principle, any visible random fluctuations of the quantities of distribution of matter and energy within the universe will be considered sufficiently small in extremely large scales. This means that the universe will be properly homogenized and isotropized due to the basic assumption that the universe is governed by the same laws of physics regardless of location, space and time.

Prior to the discovery of the Hercules–Corona Borealis Great Wall, the largest scale at which the universe showed evidence of hierarchical structure was on the scale of superclusters and filaments. At larger scales, around 250–300 million light-years, no more fractal structuring is apparent; this was called the "End of Greatness". The homogeneity exhibited at this scale and the apparent normal density of the universe (as determined by the cosmic microwave background) implied an upper homogeneity scale about 4 times as large (1 to 1.2 billion light years; 307 to 370 Mpc). Yadav et al suggested that the tips of the scales might be as well to 260/h Mpc based on the fractal dimension of the universe,[7] consistently smaller than the homogeneity scale above. Some scientists say that the maximum sizes of structures was somewhere around 70-130/h Mpc based on the measure of the homogeneity scale.[8][9][10] No structures are expected to be larger than the scale since, in accordance to the homogeneous and isotropic distribution of matter in the universe, do not expect objects to be larger than the said maximum scale. However, in spite of this, some structures are discovered that exceed the scale consistently, such as:

The Clowes–Campusano LQG, discovered in 1991, is 630 Mpc across, and is marginally larger than the scale.

The Sloan Great Wall, discovered in 2003, has a length of 423 Mpc,[11] and is marginally larger than the scale too.

U1.11, another large quasar group discovered in 2011, is 780 Mpc across, and is two times larger than the scale.

The Huge-LQG (Huge Large Quasar Group), discovered in 2012, has a length of 1.24 Gpc, and is three times larger than the upper limit of the homogeneity scale.[12] However, the scale of the individual quasars of this structure does not have a chance correlation to each other, providing the evidence of the impossibility of this structure.[13]

The Hercules–Corona Borealis Great Wall is more than eight times larger than the scale,[4] and so greatly exceeds the homogeneity scale. In accordance with this, the structure would still be heterogeneous as compared to the other parts of the universe even at the scale of the "End of Greatness", thereby putting the cosmological principle into further doubt.

Evolutionary problem[edit]

The Her-CrB GW is larger than the theoretical upper limit on how big universal structures can be... Thus, it is a conundrum: it shouldn't exist but apparently does.

Dr. Jon Hakkila, College of Charleston, South Carolina, July 15, 2014[5]

According to the modern parametrization of the Big Bang, known as the Lambda-CDM model (ΛCDM), which is currently the standard model of the evolution of the universe, the universe is defined as having dark energy represented by the Greek uppercase letter lambda (Λ), and cold dark matter (CDM). Under the model, it is assumed that such structures as galaxy filaments form along and follow web-like strings of CDM.[14] It is thought that this CDM dictates the structure of the Universe on the grandest of scales. The CDM gravitationally attracts baryonic matter, and it is this "normal" matter that astronomers see forming long, thin walls of super-galactic clusters.

The newly discovered structure, however, just doesn't simply fit to the model; the structure is so big, so complex, and so massive to exist even under the standard models of the evolution of the universe. In addition, one must also note that the light travel distance of 10 billion light years means that we see the structure as it was 10 billion years ago, or roughly 3.8 billion years after the Big Bang. Current models of the universe's evolution, however, do not allow the said structure to form in just a mere 3 billion years, since this is a very short time for dark matter to attract sufficient baryonic matter to create the giant structure. The structure is itself too big, and too complex, to exist so early in the universe. There is currently no existing model to explain the existence of the structure.[citation needed]

Evidence of a cosmic web[edit]


Such large structures like the Hercules–Corona Borealis Great Wall may form part of the vast intergalactic cosmic web, an endless continuous sheet of galaxies and dark matter. Although this web was never directly observed, the relatively large sizes of structures in the nearby universe provides the possibility of the existence of this web. Such gigaparsec-scale structures, including the Hercules–Corona Borealis Great Wall, may be the intersections of smaller subfilaments within this vast structure, where there are overdensities of galaxies connecting other filaments within this vast web. If verified, the Hercules–Corona Borealis Great Wall will be one of the first evidences of the existence of this web.

See also[edit]

References[edit]

  1. ^ a b c d e f g Horvath, Istvan; Hakkila, Jon; Bagoly, Zsolt (2014). "Possible structure in the GRB sky distribution at redshift two". Astronomy & Astrophysics 561: id.L12. arXiv:1401.0533. Bibcode:2014A&A...561L..12H. doi:10.1051/0004-6361/201323020. Retrieved 24 January 2014. 
  2. ^ a b c d e f g h i Horvath I., Hakkila J., and Bagoly Z. (2013). "The largest structure of the Universe, defined by Gamma-Ray Bursts". 7th Huntsville Gamma-Ray Burst Symposium, GRB 2013: paper 33 in eConf Proceedings C1304143. arXiv:1311.1104. Bibcode:2013arXiv1311.1104H. 
  3. ^ a b "Redshift-distance relation". 
  4. ^ a b c "Universe's Largest Structure is a Cosmic Conundrum". discovery. 2013-11-19. Retrieved 2013-11-22. 
  5. ^ a b "Biggest Thing In The Universe Is So Gigantic It Shouldn't Exist At All". The Huffington Post. 
  6. ^ Data source http://lyra.berkeley.edu/grbox/grbox.php
  7. ^ Yadav, Jaswant; J. S. Bagla and Nishikanta Khandai (25 February 2010). "Fractal dimension as a measure of the scale of Homogeneity". Monthly notices of the Royal Astronomical Society 405 (3): 2009–2015. arXiv:1001.0617. Bibcode:2010MNRAS.405.2009Y. doi:10.1111/j.1365-2966.2010.16612.x. Retrieved 15 January 2013. 
  8. ^ Hogg, D.W. et al., (May 2005) "Cosmic Homogeneity Demonstrated with Luminous Red Galaxies". The Astrophysical Journal 624: 54–58. arXiv:astro-ph/0411197. Bibcode:2005ApJ...624...54H. doi:10.1086/429084.
  9. ^ Scrimgeour, Morag I. et al., (May 2012) "The WiggleZ Dark Energy Survey: the transition to large-scale cosmic homogeneity". Monthly Notices of the Royal Astronomical Society 425 (1): 116–134. arXiv:1205.6812. Bibcode: 2012MNRAS.425...116S. doi: 10.1111/j.1365-2966.2012.21402.x.
  10. ^ Nadathur, Seshadri, (July 2013) "Seeing patterns in noise: gigaparsec-scale 'structures' that do not violate homogeneity". Monthly Notices of the Royal Astronomical Society in press. arXiv:1306.1700. Bibcode: 2013MNRAS.tmp.1690N. doi: 10.1093/mnras/stt1028.
  11. ^ Gott, J. Richard, III et al. (May 2005). "A Map of the Universe". The Astrophysical Journal 624 (2): 463–484. arXiv:astro-ph/0310571. Bibcode:2005ApJ...624..463G. doi:10.1086/428890 
  12. ^ Clowes, Roger; Harris; Raghunathan; Campusano; Soechting; Graham; Kathryn A. Harris, Srinivasan Raghunathan, Luis E. Campusano, Ilona K. Söchting and Matthew J. Graham (2012-01-11). "A structure in the early Universe at z ∼ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology". Monthly notices of the royal astronomical society 1211 (4): 6256. arXiv:1211.6256. Bibcode:2012arXiv1211.6256C. doi:10.1093/mnras/sts497. Retrieved 14 January 2013. 
  13. ^ Gaite, Jose, Dominguez, Alvaro and Perez-Mercader, Juan (August 1999) "The fractal distribution of galaxies and the transition to homogeneity". The Astrophysical Journal 522: L5-L8. arXiv:astroph/9812132. Bibcode: 1999ApJ...522L...5G. doi: 10.1086/312204.
  14. ^ Riordan, Michael; David N. Schramm (March 1991). Shadows of Creation: Dark Matter and the Structure of the Universe. W H Freeman & Co (Sd). ISBN 0-7167-2157-0.