螺旋星系
參考資料

↑  Hubble, E.P. . Mrs. Hepsa Ely Silliman memorial lectures, 25. New Haven: Yale University Press. 1936  [2017-07-31]. ISBN 9780300025002. OCLC 611263346. （原始内容存档于2019-06-02）. (pp. 124–151)
↑  D. Mihalas. . W. H. Freeman. 1968. ISBN 978-0-7167-0326-6.
↑  . Science Daily. 16 January 2014  [2017-07-31]. （原始内容存档于2021-04-19）.
↑  Ripples in a Galactic Pond （页面存档备份，存于）, Scientific American, October 2005
↑  R. A. Benjamin; E. Churchwell; B. L. Babler; R. Indebetouw; M. R. Meade; B. A. Whitney; C. Watson; M. G. Wolfire; M. J. Wolff; R. Ignace; T. M. Bania; S. Bracker; D. P. Clemens; L. Chomiuk; M. Cohen; J. M. Dickey; J. M. Jackson; H. A. Kobulnicky; E. P. Mercer; J. S. Mathis; S. R. Stolovy; B. Uzpen. . The Astrophysical Journal Letters. September 2005, 630 (2): L149–L152. Bibcode:2005ApJ...630L.149B. arXiv:astro-ph/0508325 . doi:10.1086/491785.
↑  Loveday, J. . Monthly Notices of the Royal Astronomical Society. February 1996, 278 (4): 1025–1048. Bibcode:1996MNRAS.278.1025L. arXiv:astro-ph/9603040 . doi:10.1093/mnras/278.4.1025.
↑  Dressler, A. . The Astrophysical Journal. March 1980, 236: 351–365. Bibcode:1980ApJ...236..351D. doi:10.1086/157753.
↑  .   [11 August 2015]. （原始内容存档于2020-11-08）.
↑  "Recent work has shown that the Milky Way and the Andromeda galaxies both possess the unexpected property that their dwarf satellite galaxies are aligned in thin and kinematically coherent planar structures." http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13481.html

"The origin of planar dwarf galaxy structures remains unexplained in the standard paradigm of galaxy formation." http://arxiv.org/abs/1406.1799 （页面存档备份，存于）

"This is a big problem that contradicts our standard cosmological models. It challenges our understanding of how the universe works including the nature of dark matter." Geraint F. Lewis quoted in http://phys.org/news/2014-07-mysterious-dwarfs-cosmic-rethink.html （页面存档备份，存于）

"There's a very serious conflict, and the repercussion is we do not seem to have the correct theory of gravity" Pavel Kroupa as quoted in http://phys.org/news/2014-06-universe-dwarf-galaxies-dont-standard.html （页面存档备份，存于）
↑  Oldest spiral galaxy is a freak of cosmos http://www.zmescience.com/space/oldest-spiral-galaxy-31321/ （页面存档备份，存于）
↑  Gonzalez, Robert T. . io9. 19 July 2012  [10 September 2012]. （原始内容存档于2015-12-12）.
↑  . ESA / Hubble.   [2 April 2014]. （原始内容存档于2017-10-25）.
↑  Lin, C. C.; Shu, F. H. . The Astrophysical Journal. August 1964, 140: 646–655. Bibcode:1964ApJ...140..646L. doi:10.1086/147955.
↑  Henbest, Nigel, , Cambridge University Press: 74, 1994  [2017-08-02], ISBN 9780521458825, （原始内容存档于2019-06-12）, Lin and Shu showed that this spiral pattern would persist more or less for ever, even though individual stars and gas clouds are always drifting into the arms and out again .
↑  Francis, C.; Anderson, E. . Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 2009, 465 (2111): 3425. Bibcode:2009RSPSA.465.3425F. arXiv:0901.3503 . doi:10.1098/rspa.2009.0036.
↑  Freeman, K. C. . Astrophysical Journal. 1970, 160: 811. Bibcode:1970ApJ...160..811F. doi:10.1086/150474.
↑  .   [2017-08-03]. （原始内容存档于2021-02-27）.
↑  Hubble, E. P. . The Astrophysical Journal. May 1926, 63: 236–274. Bibcode:1926ApJ....63..236H. doi:10.1086/142976.
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↑  McKee, Maggie. . New Scientist. August 16, 2005  [17 June 2009]. （原始内容存档于2015-07-01）.
↑  Thomas, Sunil. . Russian J Phys Chem B. 2017, 11: 195–198  [2017-08-03]. doi:10.1134/S1990793117010328. （原始内容存档于2021-04-04）.