View source for Astronomy:Scutum–Centaurus Arm

{{short description|Spiral arm of the Milky Way}}
[[Image:Milky Way Arms ssc2008-10.svg|400px|right|thumb|Observed structure of the Milky Way's spiral arms]]

The '''Scutum–Centaurus Arm''', also known as '''Scutum-Crux arm''', is a long, diffuse curving streamer of [[Astronomy:Star|star]]s, gas and dust that spirals outward from the proximate end of the [[Astronomy:Milky Way|Milky Way]]'s central [[Astronomy:Barred spiral galaxy|bar]]. The Milky Way has been posited since the 1950s to have four spiral arms &mdash; numerous studies contest or nuance this number.<ref name=bash>{{Cite journal | last1 = Bash | first1 = F. N. | doi = 10.1086/159401 | title = Does the Galaxy have four spiral arms | journal = The Astrophysical Journal | volume = 250 | pages = 551 | year = 1981 | bibcode = 1981ApJ...250..551B | doi-access = free }}</ref> In 2008, observations using the Spitzer Space Telescope failed to show the expected density of red clump giants in the direction of the [[Astronomy:Carina–Sagittarius Arm|Sagittarius]] and Norma arms.<ref name=benjamin>{{Cite journal | display-authors=1| last1 = Churchwell | first1 = E. | last2 = Babler | first2 = B. L. | last3 = Meade | first3 = M. R. | last4 = Whitney | first4 = B. A. | last5 = Benjamin | first5 = R. | last6 = Indebetouw | first6 = R. | last7 = Cyganowski | first7 = C. | last8 = Robitaille | first8 = T. P. | last9 = Povich | first9 = M. | doi = 10.1086/597811 | title = The Spitzer/GLIMPSE surveys: a new view of the Milky Way | journal = Publications of the Astronomical Society of the Pacific | volume = 121 | issue = 877 | pages = 213 | year = 2009 | bibcode=2009PASP..121..213C}}</ref> In January 2014, a 12-year study into the distribution and lifespan of massive stars<ref>{{Cite journal | last1 = Urquhart | first1 = J. S. | last2 = Figura | first2 = C. C. | last3 = Moore | first3 = T. J. T. | last4 = Hoare | first4 = M. G. | last5 = Lumsden | first5 = S. L. | last6 = Mottram | first6 = J. C. | last7 = Thompson | first7 = M. A. | last8 = Oudmaijer | first8 = R. D. | doi = 10.1093/mnras/stt2006 | title = The RMS survey: Galactic distribution of massive star formation | journal = Monthly Notices of the Royal Astronomical Society | volume = 437 | issue = 2 | pages = 1791 | year = 2013 | bibcode = 2014MNRAS.437.1791U |arxiv = 1310.4758 }}</ref> and a 2013-reporting study of the distribution of masers and open clusters<ref name=bobylev>{{Cite journal | last1 = Bobylev | first1 = V. V. | last2 = Bajkova | first2 = A. T. | title = The Milky Way spiral structure parameters from data on masers and selected open clusters | doi = 10.1093/mnras/stt1987 | journal = Monthly Notices of the Royal Astronomical Society | volume = 437 | issue = 2 | pages = 1549 | year = 2013 | bibcode = 2014MNRAS.437.1549B |arxiv = 1310.3974 }}</ref> both found corroboratory, though would not state irrefutable, evidence for four principal spiral arms.

The Scutum–Centaurus Arm lies between the minor Carina–Sagittarius Arm and the major [[Astronomy:Perseus Arm|Perseus Arm]]. The Scutum–Centaurus Arm starts near the core as the ''Scutum Arm'', then gradually turns into the ''Centaurus Arm''.<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}}</ref>

The region where the Scutum–Centaurus Arm connects to the bar of the galaxy is rich in [[Astronomy:Star formation|star-forming region]]s and open clusters. In 2006 a large cluster of new stars containing 14 [[Astronomy:Red supergiant|red supergiant]] stars was discovered there and named [[Astronomy:RSGC1|RSGC1]]. In 2007 a cluster of approximately 50,000 newly formed stars named [[Astronomy:Stephenson 2|RSGC2]] was located only a few hundred light years from RSGC1.  It is thought to be less than 20 million years old and contains 26 red supergiant stars, the largest grouping of such stars known.<ref name=davies>{{Cite journal | last1 = Davies | first1 = B. | last2 = Figer | first2 = D. F. | last3 = Kudritzki | first3 = R. P. | last4 = MacKenty | first4 = J. | last5 = Najarro | first5 = F. | last6 = Herrero | first6 = A. | doi = 10.1086/522224 | title = A Massive Cluster of Red Supergiants at the Base of the Scutum‐Crux Arm | journal = The Astrophysical Journal | volume = 671 | issue = 1 | pages = 781–801 | year = 2007 | bibcode=2007ApJ...671..781D|arxiv = 0708.0821 | s2cid = 1447781 }}</ref> Other clusters in this region include [[Astronomy:RSGC3|RSGC3]] and [[Astronomy:Alicante 8|Alicante 8]].<ref name=Negueruela2010>{{Cite journal | volume = 513 | journal = Astronomy and Astrophysics | title = Another cluster of red supergiants close to RSGC1 | pages = A74 | year = 2010| bibcode = 2010A&A...513A..74N | doi = 10.1051/0004-6361/200913373 | first5 = S. | last5 = Martínez-Núñez | first2 = C. | last2 = González-Fernández | first1 = I. | last3 = Marco | first3 = A. | first4 = J. S. | last4 = Clark | last1 = Negueruela|arxiv = 1002.1823 | s2cid = 118531372 }}</ref>

==See also==
*[[Astronomy:Galactic disc|Galactic disc]]

==References==
{{Reflist}}

{{Milky Way}}
{{DEFAULTSORT:Scutum-Centaurus Arm}}
[[Category:Scutum–Centaurus Arm| ]]
[[Category:Milky Way arms]]
[[Category:Galactic astronomy]]
[[Category:Spiral galaxies]]

{{Sourceattribution|Scutum–Centaurus Arm}}