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Observation data (J2000 epoch)
Constellation Scutum
Right ascension 18h 45m 24.0s[1]
Declination −03° 23′ 13.2″[1]
Distance 22+12
kly (6[1] - 7.0+3.7
Apparent magnitude (V) not visible[2]
Apparent dimensions (V) 1.8'[1]
Physical characteristics
Mass ~2 × 104[2] M
Radius ~2 pc[2]
Estimated age 18–24 my[2][1]
See also: Open cluster, List of open clusters

RSGC3 is a young massive open cluster belonging to the Milky Way galaxy. It was discovered in 2010 in the GLIMPSE survey data.[2][3] The cluster is located in the constellation Scutum at the distance of about 7 kpc from the Sun. It is likely situated at the intersection of the northern end of the Long Bar of the Milky Way and the inner portion of the Scutum–Centaurus Arm—one of its two major spiral arms.[2][3]

The age of RSGC3 is estimated at 18–24 million years. The 16 detected red supergiant cluster members with masses of about 12–15 M are type II supernova progenitors. The cluster is heavily obscured and has not been detected in the visible light. It lies close to other groupings of red supergiants known as RSGC1, Stephenson 2 and Alicante 8. The total mass of RSGC3 is estimated at 20 thousand solar masses, which makes it one of the most massive open clusters in the Galaxy.[2]

More work has identified a population of at least 30 additional red supergiants in the vicinity of RSGC3, 7 of which are tightly grouped and have been assumed to form a cluster name Alicante 7.[4] The number of red supergiants identified in the several small areas studied in this region of the sky forms a significant fraction of all those known in the galaxy, suggesting very unusual properties for the region near the end of the galactic bar.


  1. ^ a b c d e Froebrich, D.; Scholz, A. (2013). "The main sequence of three red supergiant clusters". Monthly Notices of the Royal Astronomical Society. 436 (2): 1116–1122. Bibcode:2013MNRAS.436.1116F. ISSN 0035-8711. arXiv:1308.6436Freely accessible. doi:10.1093/mnras/stt1633. 
  2. ^ a b c d e f g h Alexander, M. J.; Kobulnicky, H. A.; Clemens, D. P.; Jameson, K.; Pinnick, A.; Pavel, M. (2009). "The Discovery of a Massive Cluster of Red Supergiants with Glimpse". The Astronomical Journal. 137 (6): 4824. Bibcode:2009AJ....137.4824A. arXiv:0903.2496Freely accessible. doi:10.1088/0004-6256/137/6/4824. 
  3. ^ a b Clark, J. S.; Negueruela, I.; Davies, B.; Larionov, V. M.; Ritchie, B. W.; Figer, D. F.; Messineo, M.; Crowther, P. A.; Arkharov, A. A. (2009). "A third red supergiant rich cluster in the Scutum-Crux arm". Astronomy and Astrophysics. 498: 109. Bibcode:2009A&A...498..109C. arXiv:0903.1754Freely accessible. doi:10.1051/0004-6361/200911945. 
  4. ^ Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S. (2011). "A massive association around the obscured open cluster RSGC3". Astronomy & Astrophysics. 528: A59. Bibcode:2011A&A...528A..59N. arXiv:1102.0028Freely accessible. doi:10.1051/0004-6361/201016102.