Editing Virgo Supercluster (section)

==Cosmology==

===Large-scale dynamics===
Since the late 1980s it has been apparent that not only the [[Local Group]], but all matter out to a distance of at least 50 [[Parsec|Mpc]] is experiencing a bulk flow on the order of 600&nbsp;km/s in the direction of the [[Norma Cluster| Norma Cluster (Abell 3627)]].<ref name="plionis91">
{{cite journal
 | author = Plionis, Manolis
 | author2 = Valdarnini, Riccardo
 | title = Evidence for large-scale structure on scales about 300/h MPC
 | journal = Monthly Notices of the Royal Astronomical Society
 | date = March 1991
 | volume = 249
 | pages = 46–61
 | bibcode = 1991MNRAS.249...46P
 | doi =10.1093/mnras/249.1.46
 | doi-access = free
 }}</ref>
Lynden-Bell et al. (1988) dubbed the cause of this the "[[Great Attractor]]". The Great Attractor is now understood to be the center of mass of an even larger structure of galaxy clusters, dubbed "[[Laniakea Supercluster|Laniakea]]", which includes the Virgo Supercluster (including the Local Group) as well as the Hydra-Centaurus Supercluster, the Pavo-Indus Supercluster, and the Fornax Group.

The Great Attractor, together with the entire supercluster, is found to be moving toward [[Shapley Supercluster]], with center of [[Shapley Attractor]].<ref>{{Cite web|url=http://www.universetoday.com/113150/what-is-the-great-attractor/|title = What is the Great Attractor?|date = 14 July 2014}}</ref>

===Dark matter===
The LS has a total mass ''M'' ≈ 10<sup>15</sup> {{solar mass|link=yes}} and a total optical luminosity ''L'' ≈ 3{{e|12}} {{solar luminosity|link=yes}}.<ref name="ein07" /> This yields a [[mass-to-light ratio]] of about 300 times that of the solar ratio ({{solar mass}}/{{solar luminosity}} = 1), a figure that is consistent with results obtained for other superclusters.<ref name="todd98">
{{cite journal
 | author = Small, Todd A.
 | display-authors = etal
 | title = The Norris Survey of the Corona Borealis Supercluster. III. Structure and Mass of the Supercluster
 | journal = Astrophysical Journal
 | date = Jan 1998
 | volume = 492
 | issue = 1| pages = 45–56
 | bibcode = 1998ApJ...492...45S
 | doi = 10.1086/305037
 | arxiv = astro-ph/9708153
| s2cid = 119451873
 }}</ref><ref name="heymans08">
{{cite journal
 | author = Heymans, Catherine
 | display-authors = etal
 | title = The dark matter environment of the A901 abell A901/902 supercluster: a weak lensing analysis of the HST STAGES survey
 | journal = [[Monthly Notices of the Royal Astronomical Society]]
 | date = April 2008
 | volume = 385
 | issue = 3
 | pages = 1431–1442
 | bibcode = 2008MNRAS.385.1431H
 | doi = 10.1111/j.1365-2966.2008.12919.x
| doi-access = free
 |arxiv = 0801.1156 | s2cid = 59057342
 }}</ref>
By comparison, the [[mass-to-light ratio]] for the [[Milky Way]] is 63.8 assuming a solar [[absolute magnitude]] of 4.83,<ref name=nssdc>
{{cite web
 | last = Williams
 | first = D. R.
 | date = 2004
 | title = Sun Fact Sheet
 | url = http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
 | publisher = [[NASA]]
 | access-date = 2012-03-17
}}</ref> a Milky Way absolute magnitude of −20.9,<ref>{{cite web
 | url = http://www.universetoday.com/guide-to-space/the-universe/absolute-magnitude/
 | title = Absolute Magnitude
 | author = Jerry Coffey
 | access-date = 2010-04-09
}}</ref>
and a Milky Way mass of {{Solar mass|1.25{{e|12}}}}.<ref name=McMillan2011>{{citation
 | last1 = McMillan
 | first1 = Paul J.
 | title = Mass models of the Milky Way
 | journal = Monthly Notices of the Royal Astronomical Society
 | volume = 414
 | issue = 3
 | pages = 2446–2457
 |date=July 2011
 | doi = 10.1111/j.1365-2966.2011.18564.x
 | doi-access = free
 | bibcode = 2011MNRAS.414.2446M |arxiv = 1102.4340 | s2cid = 119100616
 }}</ref> These ratios are one of the main arguments in favor of the presence of large amounts of [[dark matter]] in the universe; if dark matter did not exist, much smaller mass-to-light ratios would be expected.