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Stephenson 2

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Stephenson 2
Observation data (J2000 epoch)
Right ascension18h 39m 21.12s[1]
Declination−06° 01′ 44.4″[1]
Distance~20 kly (~6 kpc[2])
Apparent magnitude (V)not visible[2]
Apparent dimensions (V)1.8'[1]
Physical characteristics
Mass3–5 × 104[2] M☉
Radius~4 pc[2]
Estimated age14–20 my[2][1]
Other designationsRSGC2
Associations
ConstellationScutum
See also: Open cluster, List of open clusters

Stephenson 2 also known as RSGC2 is a young massive open cluster belonging to the Milky Way galaxy. It was discovered in 1990 in the data obtained by a deep infrared survey.[2][3] The cluster is located in the constellation Scutum at the distance of about 6 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 the two major spiral arms.[2]

26 red supergiants have been confirmed as members of the cluster, far more than any other known cluster. A more recent study has identified around 80 red supergiants in the line of sight of Stephenson 2, approximately 40 of them with radial velocities consistent with being cluster members. However these stars are spread over a wider area than a typical cluster, indicating an extended stellar association similar to that found around the nearby cluster RSGC3.[4]

The age of Stephenson 2 is estimated at 14–20 million years. The observed red supergiants with the mass of about 12–16 solar masses are type II supernova progenitors. The cluster is heavily obscured and have not been detected in the visible light. It lies close to other groupings of red super giants known as RSGC1, RSGC3 and Alicante 8.[5] The mass of the open cluster is estimated at 30–50 thousand solar masses,[2] which makes it the second most massive open cluster in the Galaxy.[citation needed]

References

  1. ^ a b c d Froebrich, D.; Scholz, A. (2013). "The main sequence of three red supergiant clusters". Monthly Notices of the Royal Astronomical Society. 436 (2): 1116–1122. arXiv:1308.6436. Bibcode:2013MNRAS.436.1116F. doi:10.1093/mnras/stt1633. ISSN 0035-8711.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  2. ^ a b c d e f g h 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: 781. arXiv:0708.0821. Bibcode:2007ApJ...671..781D. doi:10.1086/522224. {{cite journal}}: |format= requires |url= (help)
  3. ^ Stephenson, C. B. (1990). "A possible new and very remote galactic cluster". The Astronomical Journal. 99: 1867. Bibcode:1990AJ.....99.1867S. doi:10.1086/115464.
  4. ^ Negueruela, I.; Marco, A.; González-Fernández, C.; Jiménez-Esteban, F.; Clark, J. S.; Garcia, M.; Solano, E. (2012). "Red supergiants around the obscured open cluster Stephenson 2". Astronomy & Astrophysics. 547: A15. arXiv:1208.3282. Bibcode:2012A&A...547A..15N. doi:10.1051/0004-6361/201219540.
  5. ^ Negueruela, I.; González-Fernández, C.; Marco, A.; Clark, J. S.; Martínez-Núñez, S. (2010). "Another cluster of red supergiants close to RSGC1". Astronomy and Astrophysics. 513: A74. arXiv:1002.1823. Bibcode:2010A&A...513A..74N. doi:10.1051/0004-6361/200913373.


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