Astronomy:Local Void

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Short description: Vast void adjacent to the Local Group


Local Void
Observation data
(Epoch J2000.0[1])
 18h 38m[1]
Declination+18.0°[1]
In visual light (V)
Size
60 Mpc (200 Mly)[2]
[edit on Wikidata]

The Local Void is a vast, empty region of space, lying adjacent to the Local Group.[3][4] Discovered by Brent Tully and Rick Fisher in 1987,[5] the Local Void is now known to be composed of three separate sectors, separated by bridges of "wispy filaments".[4] The precise extent of the void is unknown, but it is at least 45 Mpc (150 million light-years) across,[6] and possibly 150 to 300 Mpc.[7][8] The Local Void appears to have significantly fewer galaxies than expected from standard cosmology.[9]

Location and dimensions

Voids are affected by the way gravity causes matter in the universe to "clump together", herding galaxies into clusters and chains, which are separated by regions mostly devoid of galaxies, yet the exact mechanisms are subject to scientific debate.[3][10]

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.[3] The Local Void extends approximately 60 megaparsecs (200 Mly), beginning at the edge of the Local Group.[11] It is believed that the distance from Earth to the centre of the Local Void must be at least 23 megaparsecs (75 Mly).[4]

The size of the Local Void was calculated due to an isolated dwarf galaxy known as ESO 461-36 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, yet discrepancies give room for competing theories.[4] Dark energy has been suggested as one alternative explanation for the speedy expulsion of the dwarf galaxy.[3]

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.[12]

Several authors have shown that the local universe up to 300 Mpc from the Milky Way is less dense than surrounding areas – by 15–50%. This has been called the Local Void or Local Hole.[7][8] Some media reports have dubbed it the KBC Void,[13] although this name has not been taken up in other publications.[citation needed]

Effect on surroundings

Scientists believe that the Local Void is growing and that the Local Sheet, which makes up one wall of the void, is rushing away from the void's centre at 260 kilometres per second (160 mi/s).[10] 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.[4] The Milky Way's velocity away from the Local Void is 970,000 kilometres per hour (600,000 mph).[3][6]

List of void galaxies

This list is incomplete; you can help by expanding it.

Several void galaxies have been found within the Local Void. These include:

Galaxy Constellation Declination Distance Right ascension Notes
Pisces A Pisces +10° 48′ 47.01″ 18.4 Mly (5.64 Mpc) 00h 14m 46.000s The two void dwarf galaxies located in the Local Void and are in the Pisces constellation. Pisces A is 18.4 million light-years (5.64 megaparsecs) away and Pisces B is 30 million light-years (9.2 megaparsecs) away. The galaxies were discovered with the WIYN Observatory. About 100 million years ago, they started moving out of the void and into the local filament zone and denser gaseous environment. This sparked off a doubling of the rate of star formation.[14]
Pisces B +11° 07′ 18.22″ 30 Mly (9.2 Mpc) 01h 19m 11.700s
NGC 7077 Aquarius 02° 24′ 51″ 56 Mly (17.2 Mpc) 21h 29m 59.6s
NGC 6503 Draco +70° 08′ 39.587″ 13.05 ± 0.33 Mly (4.0 ± 0.1 Mpc) 17h 49m 26.4207s A field[15] dwarf spiral galaxy located at the edge of a region of space called the Local Void. The dwarf galaxy spans 30,000 light-years and lies approximately 17 million light-years away in the constellation of Draco (the Dragon). This spiral galaxy is especially colorful where bright red regions of gas can be seen scattered through its spiral arms. Bright blue regions contain stars that are forming. Dark brown dust areas are in the galaxy's arms and center. It has one known satellite galaxy, known as KK 242. With a stellar mass of about 3 million solar masses, KK 242 is on the border between a dwarf irregular galaxy (dIrr) and a dwarf spheroidal galaxy (dSph).[16]
NGC 6789 +63° 58′ 23″ 12 Mly (3.6 Mpc) 19h 16m 41s An irregular galaxy in the constellation Draco. It was discovered by Lewis Swift on 30 August 1883. It is located within the Local Void, a region of space with far fewer galaxies than its surroundings. It is the nearest blue compact dwarf (BCD) galaxy to the Milky Way. It is chemically homogeneous and relatively metal-poor.[17]

See also

References

  1. ↑ 1.0 1.1 1.2 "NAME Local Void". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NAME+Local+Void. 
  2. ↑ Nakanishi, Kouichiro et al. (1 October 1997). "Search and Redshift Survey for IRAS Galaxies behind the Milky Way and Structure of the Local Void". The Astrophysical Journal Supplement Series 112 (2): 245. doi:10.1086/313039. Bibcode: 1997ApJS..112..245N. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Shiga, David (1 June 2007). "Dwarf-flinging void is larger than thought". New Scientist. https://www.newscientist.com/article/dn11971-dwarfflinging-void-is-larger-than-thought.html. Retrieved 13 October 2008. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Tully, R. Brent et al. (20 March 2008). "Our Peculiar Motion Away from the Local Void". The Astrophysical Journal 676 (1): 184–205. doi:10.1086/527428. Bibcode: 2008ApJ...676..184T. 
  5. ↑ Tully, R. Brent; Fisher, J. Richard (1987). Nearby Galaxy Atlas. Cambridge University Press. Bibcode: 1987nga..book.....T. http://ned.ipac.caltech.edu/level5/March04/Virgo_cluster/frames.html. 
  6. ↑ 6.0 6.1 "Milky Way moving away from void". Astronomy. 12 June 2007. https://astronomy.com/news-observing/news/2007/06/milky%20way%20moving%20away%20from%20void. Retrieved 13 October 2008. 
  7. ↑ 7.0 7.1 Whitbourn, Joe R.; Shanks, Tom (June 2016). "The galaxy luminosity function and the Local Hole". Monthly Notices of the Royal Astronomical Society 459 (1): 496. doi:10.1093/mnras/stw555. Bibcode: 2016MNRAS.459..496W. 
  8. ↑ 8.0 8.1 Keenan, Ryan C.; Barger, Amy J.; Cowie, Lennox L. (5 September 2013). "Evidence for a ~300 Mpc Scale Under-density in the Local Galaxy Distribution". The Astrophysical Journal 775 (1): 62. doi:10.1088/0004-637X/775/1/62. Bibcode: 2013ApJ...775...62K. 
  9. ↑ Peebles, P. J. E.; Nusser, Adi (June 2010). "Nearby galaxies as pointers to a better theory of cosmic evolution". Nature 465 (7298): 565–569. doi:10.1038/nature09101. PMID 20520705. Bibcode: 2010Natur.465..565P. 
  10. ↑ 10.0 10.1 Iwata, Ikuru; Ohta, Kouji; Nakanishi, Kouichiro; Chamaraux, Pierre; Roman, Adel T. (2005). "The Growth of the Local Void and the Origin of the Local Velocity Anomaly". Nearby Large-Scale Structures and the Zone of Avoidance. 329. pp. 59–66. http://www.aspbooks.org/publications/329/059.pdf. Retrieved 13 May 2020. 
  11. ↑ Tully, Brent. "Our CMB Motion: The Local Void influence". Institute for Astronomy. http://www.astro.rug.nl/~weygaert/tim1publication/knawvoid/voidknaw.tully.ppt. Retrieved 13 October 2008. 
  12. ↑ Moss, Adam; Zibin, James P.; Scott, Douglas (15 May 2011). "Precision Cosmology Defeats Void Models for Acceleration". Physical Review D 83 (10): 103515. doi:10.1103/PhysRevD.83.103515. Bibcode: 2011PhRvD..83j3515M. 
  13. ↑ Siegel, Ethan (7 June 2017). "We're Way Below Average! Astronomers Say Milky Way Resides in a Great Cosmic Void". Forbes. https://www.forbes.com/sites/startswithabang/2017/06/07/were-way-below-average-astronomers-say-milky-way-resides-in-a-great-cosmic-void/#. Retrieved 9 June 2017. 
  14. ↑ "Hubble Sees Two Dwarf Galaxies in Pisces". Sci-News. 15 August 2016. http://www.sci-news.com/astronomy/hubble-dwarf-galaxies-pisces-04103.html. 
  15. ↑ Materne, J. (April 1979). "The structure of nearby groups of galaxies – Quantitative membership probabilities". Astronomy and Astrophysics 74 (2): 235–243. Bibcode: 1979A&A....74..235M. 
  16. ↑ Jenner, Lynn, ed (10 June 2015). "Lonely Galaxy Lost in Space". NASA. https://www.nasa.gov/image-feature/goddard/lonely-galaxy-lost-in-space. 
  17. ↑ Lelli, Federico; Verheijen, Marc; Fraternali, Filippo (2014). "The triggering of starbursts in low-mass galaxies". Monthly Notices of the Royal Astronomical Society 445 (2): 1694–1712. doi:10.1093/mnras/stu1804. Bibcode: 2014MNRAS.445.1694L. 



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