TheScutum–Centaurus Arm, also known asScutum-Crux arm, is a long, diffuse curving streamer ofstars, gas and dust that spirals outward from the proximate end of theMilky Way's centralbar. The Milky Way has been posited since the 1950s to have fourspiral arms; numerous studies contest or nuance this number.[1] In 2008, observations using the Spitzer Space Telescope failed to show the expected density of red clump giants in the direction of theCarina–Sagittarius Arm andNorma Arm.[2] In January 2014, a 12-year study into the distribution and lifespan of massive stars[3] and a 2013-reporting study of the distribution of masers and open clusters[4] 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 minorNorma Arm. The Scutum–Centaurus Arm starts near the core as theScutum Arm, then gradually turns into theCentaurus Arm.[5]
The region where the Scutum–Centaurus Arm connects to the bar of the galaxy is rich instar-forming regions andopen clusters. In 2006 a large cluster of new stars containing 14red supergiant stars was discovered there and namedRSGC1. In 2007 a cluster of approximately 50,000 newly formed stars namedRSGC2 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.[6] Other clusters in this region includeRSGC3 andAlicante 8.[7]
^Churchwell, E.; et al. (2009). "The Spitzer/GLIMPSE surveys: a new view of the Milky Way".Publications of the Astronomical Society of the Pacific.121 (877): 213.Bibcode:2009PASP..121..213C.doi:10.1086/597811.
^Davies, B.; Figer, D. F.; Kudritzki, R. P.; MacKenty, J.; Najarro, F.; Herrero, A. (2007). "A Massive Cluster of Red Supergiants at the Base of the Scutum-Crux Arm".The Astrophysical Journal.671 (1):781–801.arXiv:0708.0821.Bibcode:2007ApJ...671..781D.doi:10.1086/522224.S2CID1447781.
