Void (astronomy)

This article is about astronomical voids. For other uses, see Void.
"Super void" redirects here. Not to be confused with Great Void or Giant Void.
For various cosmic voids, see List of voids.
Structure of the Universe
Simulation of the matter distribution in a cubic section of the universe. The blue fiber structures represent the matter (primarily dark matter) and the empty regions in between represent the cosmic voids.
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Cosmic voids (also known as dark space) are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies. In spite of their size, most galaxies are not located in voids. This is because most galaxies are gravitationally bound together, creating huge cosmic structures known as galaxy filaments. The cosmological evolution of the void regions differs drastically from the evolution of the universe as a whole: there is a long stage when the curvature term dominates, which prevents the formation of galaxy clusters and massive galaxies. Hence, although even the emptiest regions of voids contain more than ~15% of the average matter density of the universe, the voids look almost empty to an observer.[1]

Voids typically have a diameter of 10 to 100 megaparsecs (30 to 300 million light-years); particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. They were first discovered in 1978 in a pioneering study by Stephen Gregory and Laird A. Thompson at the Kitt Peak National Observatory.[2]

Voids are believed to have been formed by baryon acoustic oscillations in the Big Bang, collapses of mass followed by implosions of the compressed baryonic matter. Starting from initially small anisotropies from quantum fluctuations in the early universe, the anisotropies grew larger in scale over time. Regions of higher density collapsed more rapidly under gravity, eventually resulting in the large-scale, foam-like structure or "cosmic web" of voids and galaxy filaments seen today. Voids located in high-density environments are smaller than voids situated in low-density spaces of the universe.[3]

Voids appear to correlate with the observed temperature of the cosmic microwave background (CMB) because of the Sachs–Wolfe effect. Colder regions correlate with voids, and hotter regions correlate with filaments because of gravitational redshifting. As the Sachs–Wolfe effect is only significant if the universe is dominated by radiation or dark energy, the existence of voids is significant in providing physical evidence for dark energy.[4][5]

  1. ^ Baushev, A. N. (2021). "The central region of a void: an analytical solution". Monthly Notices of the Royal Astronomical Society: Letters. 504 (1): L56–L60. arXiv:2104.01359. Bibcode:2021MNRAS.504L..56B. doi:10.1093/mnrasl/slab036.
  2. ^ Freedman, Roger A.; Kaufmann, William J. (2008). Universe. Stars and galaxies (3rd ed.). New York: W.H. Freeman. ISBN 978-0-7167-9561-2.
  3. ^ Lindner, Ulrich; Einasto, Jaan; Einasto, Maret; Freudling, Wolfram; Fricke, Klaus; Tago, Erik (1995). "The structure of supervoids. I. Void hierarchy in the Northern Local Supervoid". Astronomy and Astrophysics. 301: 329. arXiv:astro-ph/9503044. Bibcode:1995A&A...301..329L.
  4. ^ Granett, B. R.; Neyrinck, M. C.; Szapudi, I. (2008). "An Imprint of Superstructures on the Microwave Background due to the Integrated Sachs-Wolfe Effect". Astrophysical Journal. 683 (2): L99–L102. arXiv:0805.3695. Bibcode:2008ApJ...683L..99G. doi:10.1086/591670. S2CID 15976818.
  5. ^ Sahlén, Martin; Zubeldía, Íñigo; Silk, Joseph (2016). "Cluster–Void Degeneracy Breaking: Dark Energy, Planck, and the Largest Cluster and Void". The Astrophysical Journal Letters. 820 (1): L7. arXiv:1511.04075. Bibcode:2016ApJ...820L...7S. doi:10.3847/2041-8205/820/1/L7. ISSN 2041-8205. S2CID 119286482.