Editing Norma Arm

{{More citations needed|date=December 2009}}
[[Image:Milky Way Arms ssc2008-10.svg|300px|right|thumb|Diagram of the [[Milky Way]]'s spiral arms]]
{{Short description|Minor spiral arm of the Milky Way galaxy}}

The '''Norma Arm''' is a minor [[spiral arm]] of the [[Milky Way]] extending from and around its central hub region.<ref name=Churchwell2009>{{cite journal|last=Churchwell|first=Ed|author2=Babler, Brian L. |author3=Meade, Marlin A. |title=The Spitzer/GLIMPSE Surveys: A New View of the Milky Way|journal=Publications of the Astronomical Society of the Pacific|year=2009|volume=121|issue=877 |pages=213–230|doi=10.1086/597811|url=http://www.astro.wisc.edu/sirtf/Churchwell_2009.pdf|bibcode=2009PASP..121..213C|s2cid=15529740 }}</ref> The inner portion of the Arm is called the ''Norma Arm'' in narrow meaning. The outer end of it is identified either with the '''Cygnus Arm''' (not to be confused with local and minor [[Orion-Cygnus Arm]]), which lies outside the [[Perseus Arm]], or the '''Outer Arm''', which is located farther away from the center of the Galaxy than the Cygnus Arm.<ref name=Churchwell2009/> The Norma Arm begins {{Val|2.2|ul=kpc}} from the [[Galactic Center]],<ref name=Vallée2017>{{cite journal | title=The Norma spiral arm: large-scale pitch angle | last=Vallée | first=Jacques P. | journal=Astrophysics and Space Science | volume=362 | issue=9 | id=173 | pages=5 | date=September 2017 | doi=10.1007/s10509-017-3145-5 | arxiv=1708.07189  | bibcode=2017Ap&SS.362..173V | s2cid=254256961 }}</ref> and extends outward to a radius of {{Val|15.5|2.8|u=kpc}}. It is named for the [[Norma (constellation)|Norma]] constellation, through which the Arm as seen from Earth passes.

Like many other galaxies of similar type, the Milky Way consists of a large mass of [[star]]s shaped into the form of a relatively flat disc by [[gravity]]. The disc is rotating, with the dense central body of stars moving at greater speeds than those toward the rim of the disc.  As a result, the pattern of stars within the Galaxy as viewed from directly above or below the disc has formed into a spiral.

Because of localised gravitational variations, the spiral pattern has itself formed several distinct 'spiral arms', where particularly large numbers of stars can be found.<ref name=Churchwell2009/>

==See also==
*[[Galactic disc]]

==References==
{{Reflist}}

{{Milky Way}}
{{Portal bar|Stars|Outer space}}

[[Category:Milky Way arms]]
[[Category:Galactic astronomy]]
[[Category:Spiral galaxies]]