|18h 38m |
In visual light (V)
|60 Mpc (200 Mly) |
The Local Void is a vast, empty region of space, lying adjacent to the Local Group. Discovered by Brent Tully and Rick Fisher in 1987, the Local Void is now known to be composed of three separate sectors, separated by bridges of "wispy filaments". The precise extent of the void is unknown, but it is at least 45 Mpc (150 million light-years) across and may have a long dimension of up to 70 Mpc (230 million light-years). The Local Void also appears to have significantly fewer galaxies than expected from standard cosmology.
Location and dimensions
Astronomers have previously noticed that the Milky Way sits in a large, flat array of galaxies called the Local Sheet, which bounds the Local Void. The Local Void extends approximately 60 megaparsecs (200 Mly), beginning at the edge of the Local Group. It is believed that the distance from Earth to the centre of the Local Void must be at least 23 megaparsecs (75 Mly).
The size of the Local Void was calculated due to an isolated dwarf galaxy located inside it. The bigger and emptier the void, the weaker its gravity, and the faster the dwarf should be fleeing the void towards concentrations of matter. Dark energy has been suggested as an alternative explanation for the speedy expulsion of the dwarf galaxy.
An earlier "Hubble Bubble" model, based on measured velocities of Type 1a supernovae, proposed a relative void centred on the Milky Way. Recent analysis of that data, however, suggested that interstellar dust had resulted in misleading measurements.
Effect on surrounds
Scientists believe that the Local Void is growing and the Local Sheet, which makes up one wall of the void, is rushing away from the void's centre at 260 kilometres per second. Concentrations of matter normally pull together, creating a larger void where matter is rushing away. The Local Void is surrounded uniformly by matter in all directions, except for one sector in which there is nothing, which has the effect of taking more matter away from that sector. The effect on the nearby galaxy is astonishingly large. The Milky Way's velocity away from the Local Void is 270 kilometres per second (600,000 mph).
List of void galaxies
Several void galaxies have been found within the Local Void, these include:
- "NAME LOCAL VOID -- Underdense region of the Universe". SIMBAD. Retrieved 21 December 2014.
- Nakanishi, Kouichiro; Takata, Tadafumi; Yamada, Toru; Takeuchi, Tsutomu T.; Shiroya, Ryuichi; Miyazawa, Morio; Watanabe, Shigeo; Saito, Mamoru (1997). "Search and Redshift Survey for IRAS Galaxies behind the Milky Way and Structure of the Local Void" (PDF). Astrophysical Journal Supplement. 112: 245. Bibcode:1997ApJS..112..245N. doi:10.1086/313039.
- Shiga, David (1 June 2007). "Dwarf-flinging void is larger than thought". NewScientist.com news service. Retrieved 2008-10-13.
- Tully, R. B.; Shaya, E. J.; Karachentsev, I. D.; Courtois, H. M.; Kocevski, D. D.; Rizzi, L.; Peel, A. (2008). "Our Peculiar Motion Away from the Local Void". The Astrophysical Journal. 676: 184. arXiv: . Bibcode:2008ApJ...676..184T. doi:10.1086/527428.
- Tully, R. Brent; Fisher, J. Richard (1987). Nearby Galaxy Atlas. Cambridge University Press.
- Univ. of Hawaii Institute for Astronomy (12 June 2007). "Milky Way moving away from void". astronomy.com. Retrieved 2008-10-13.
- Peebles, P. J. E.; Nusser, A. (2010). "Nearby galaxies as pointers to a better theory of cosmic evolution". Nature. 465 (7298): 565–569. arXiv: . Bibcode:2010Natur.465..565P. doi:10.1038/nature09101. PMID 20520705.
- I, Iwata; Ohta, K.; Nakanishi, K.; Chamaraux, P.; Roman, A.T. The Growth of the Local Void and the Origin of the Local Velocity Anomaly. Nearby Large-Scale Structures and the Zone of Avoidance (329 ed.). Astronomical Society of the Pacific. p. 59.
- Tully, Brent. "Our CMB Motion: The Local Void influence". University of Hawaii, Institute for Astronomy. Retrieved 2008-10-13.
- Moss, Adam; James P Zibin; Douglas Scott (2011). "Precision Cosmology Defeats Void Models for Acceleration". Physical Review D. 83 (10). arXiv: . Bibcode:2011PhRvD..83j3515M. doi:10.1103/PhysRevD.83.103515.
- The Astrophysical Journal Letters, "Detection of X-Ray Emission from Galaxies inside the Bootes Void", Chulhee Kim, Th. Boller, Kajal K. Ghosh, Douglas A. Swartz, Brian D. Ramsey, 'Volume 546, Number 2', 10 January 2001, doi:10.1086/318868
- The Astronomical Journal, "Spectroscopy of Galaxies in the Bootes Void", Shawn Cruzen 1, Tara Wehr, Donna Weistrop, Ronald J. Angione, Charles Hoopes, 'Volume 123, Number 1', 2002 January, doi:10.1086/324739
- SIMBAD, MCG+01-02-015
- "The loneliest of galaxies". Hubble Space Telescope. 9 November 2015. Retrieved 10 November 2015.
- Sci-News, "NASA’s Hubble Space Telescope Focuses on Lonely Galaxy", 9 November 2015
- SpaceDaily, "Hubble Views a Lonely Galaxy", 18 November 2015
- "Hubble Sees Two Dwarf Galaxies in Pisces". Sci-News. 15 August 2016.