盾牌-南十字臂

盾牌-南十字臂，也稱為盾牌-半人馬臂，是從銀河系中心接近棒的末端，由瀰散的氣體和塵埃組成，向外螺旋彎曲的長串星流。儘管自20世紀50年代以來，沒有確實強而有力的證據，但銀河系一直被認為有4條螺旋臂^[1]。在2008年，利用史匹哲太空望遠鏡觀測的資料，在船底-人馬臂和矩尺臂的紅群聚沒有如預期的密度^[2]。在2014年，一項為期12年，研究大質量恆星的分佈和壽命^[3]，以及對邁射和疏散星團分佈的研究^[4]，兩者都發現4條螺旋臂的證據。

盾牌-半人馬臂位於小船底-人馬臂和主要的英仙臂之間。盾牌-半人馬臂開始的位置靠近盾牌臂的核心，然後逐漸變成半人馬臂^[5]。

盾牌-半人馬臂與銀河的棒連接的區域是豐富的恆星形成區。2006年在那兒發現一大群新恆星，其中包括有14顆紅超巨星命名為RSGC1的集團。在2007年發現距離RSGC1隻有幾百光年，擁有5,000顆新形成恆星，命名為RSGC2的集團。估計它的年齡還不到2,000萬年，並有26顆紅超巨星，是已知此種恆星的最大集團^[6]。這個區域的恆星集團還有紅超巨星團3和阿利坎特8^[7]。

參考資料

^ Bash, F. N. Does the Galaxy have four spiral arms. The Astrophysical Journal. 1981, 250: 551. Bibcode:1981ApJ...250..551B. doi:10.1086/159401.
^ Churchwell, E.; et al. The Spitzer/GLIMPSE surveys: a new view of the Milky Way. Publications of the Astronomical Society of the Pacific. 2009, 121 (877): 213. Bibcode:2009PASP..121..213C. doi:10.1086/597811.
^ Urquhart, J. S.; Figura, C. C.; Moore, T. J. T.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Oudmaijer, R. D. The RMS survey: Galactic distribution of massive star formation. Monthly Notices of the Royal Astronomical Society. 2013, 437 (2): 1791. Bibcode:2014MNRAS.437.1791U. arXiv:1310.4758 . doi:10.1093/mnras/stt2006.
^ Bobylev, V. V.; Bajkova, A. T. The Milky Way spiral structure parameters from data on masers and selected open clusters. Monthly Notices of the Royal Astronomical Society. 2013, 437 (2): 1549. Bibcode:2014MNRAS.437.1549B. arXiv:1310.3974 . doi:10.1093/mnras/stt1987.
^ Churchwell, Ed; Babler, Brian L.; Meade, Marlin A. The Spitzer/GLIMPSE Surveys: A New View of the Milky Way (pdf). Publications of the Astronomical Society of the Pacific. 2009, 121 (877): 213–230 [2019-03-05]. Bibcode:2009PASP..121..213C. doi:10.1086/597811. （原始內容存檔 (PDF)於2014-01-21）.
^ >Davies, B.; Figer, D. F.; Kudritzki, R. P.; MacKenty, J.; Najarro, F.; Herrero, A. A Massive Cluster of Red Supergiants at the Base of the Scutum‐Crux Arm. The Astrophysical Journal (pdf). 2007, 671: 781. Bibcode:2007ApJ...671..781D. arXiv:0708.0821 . doi:10.1086/522224.
^ Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S.; Martínez-Núñez, S. Another cluster of red supergiants close to RSGC1. Astronomy and Astrophysics. 2010, 513: A74. Bibcode:2010A&A...513A..74N. arXiv:1002.1823 . doi:10.1051/0004-6361/200913373.

[bash-1] Bash, F. N. Does the Galaxy have four spiral arms. The Astrophysical Journal. 1981, 250: 551. Bibcode:1981ApJ...250..551B. doi:10.1086/159401.

[benjamin-2] Churchwell, E.; et al. The Spitzer/GLIMPSE surveys: a new view of the Milky Way. Publications of the Astronomical Society of the Pacific. 2009, 121 (877): 213. Bibcode:2009PASP..121..213C. doi:10.1086/597811.

[3] Urquhart, J. S.; Figura, C. C.; Moore, T. J. T.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Oudmaijer, R. D. The RMS survey: Galactic distribution of massive star formation. Monthly Notices of the Royal Astronomical Society. 2013, 437 (2): 1791. Bibcode:2014MNRAS.437.1791U. arXiv:1310.4758 . doi:10.1093/mnras/stt2006.

[bobylev-4] Bobylev, V. V.; Bajkova, A. T. The Milky Way spiral structure parameters from data on masers and selected open clusters. Monthly Notices of the Royal Astronomical Society. 2013, 437 (2): 1549. Bibcode:2014MNRAS.437.1549B. arXiv:1310.3974 . doi:10.1093/mnras/stt1987.

[Churchwell2009-5] Churchwell, Ed; Babler, Brian L.; Meade, Marlin A. The Spitzer/GLIMPSE Surveys: A New View of the Milky Way (pdf). Publications of the Astronomical Society of the Pacific. 2009, 121 (877): 213–230 [2019-03-05]. Bibcode:2009PASP..121..213C. doi:10.1086/597811. （原始內容存檔 (PDF)於2014-01-21）.

[davies-6] >Davies, B.; Figer, D. F.; Kudritzki, R. P.; MacKenty, J.; Najarro, F.; Herrero, A. A Massive Cluster of Red Supergiants at the Base of the Scutum‐Crux Arm. The Astrophysical Journal (pdf). 2007, 671: 781. Bibcode:2007ApJ...671..781D. arXiv:0708.0821 . doi:10.1086/522224.

[Negueruela2010-7] Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S.; Martínez-Núñez, S. Another cluster of red supergiants close to RSGC1. Astronomy and Astrophysics. 2010, 513: A74. Bibcode:2010A&A...513A..74N. arXiv:1002.1823 . doi:10.1051/0004-6361/200913373.

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