Trumpler 27

Trumpler 27 is a possible open cluster in the southern constellation Scorpius. If it exists, it is a few thousand light-years away from the Sun, with estimates ranging from 3,900 light-years (1,210 kiloparsecs)[3] to 6,800 light-years (2,100 kiloparsecs)[4] The name refers to Robert Julius Trumpler's catalog of open clusters, published in 1930.[5]

Trumpler 27
Observation data (J2000 epoch)
ConstellationScorpius
Right ascension 17h 36m 20s[1]
Declination−33° 31.0′[1]
Apparent magnitude (V)6.7[1]
Apparent dimensions (V)6′ × 6′[1]
Physical characteristics
Notable featuresTrue nature is unknown[2]
Other designationsC 1732-334[1]

It was originally thought to be young open cluster in the outer edge of the Sagittarius Arm, still surrounded by interstellar matter.[5] The light from the stars is heavily extinguished and reddened by intervening interstellar dust.[4] The light coming from the stars is also significantly polarized.[6] However, a close study in 2012 could not confirm whether the stars truly form a cluster, or if they a close alignment of bright stars.[2]

Several putative member stars have been studied in closer detail. Star #1 of Trumpler 27 is CD−33° 12241, a red supergiant star with a spectral type of M0Ia.[4][7] Star #27, a blue giant star with a spectral type of O8III((f)), may be one of the most luminous stars known, with a bolometric magnitude of −10.5.[7] Star #102 is known as V925 Scorpii or HD 159378,[8] and is a rare yellow supergiant star.[9]

References
  1. "Cl Trumpler 27". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-31.
  2. Perren, G.; Vázquez, R. A.; Carraro, G. (2012). "Photometric distances to young stars in the inner Galactic disk. II. The region towards the open cluster Trumpler 27 at L = 355°". Astronomy and Astrophysics. 548: A125. arXiv:1209.3273. Bibcode:2012A&A...548A.125P. doi:10.1051/0004-6361/201219653.
  3. Morales, Esteban F. E.; Wyrowski, Friedrich; Schuller, Frederic; Menten, Karl M. (2013). "Stellar clusters in the inner Galaxy and their correlation with cold dust emission". Astronomy and Astrophysics. 560: A76. arXiv:1310.2612. Bibcode:2013A&A...560A..76M. doi:10.1051/0004-6361/201321626.
  4. Moffat, A. F. J.; Fitzgerald, M. P.; Jackson, P. D. (1977). "Trumpler 27: A heavily reddened young open cluster with blue and red supergiants". The Astrophysical Journal. 215: 106. Bibcode:1977ApJ...215..106M. doi:10.1086/155338.
  5. The, P. S.; Stokes, N. (1970). "A study of the southern open clusters : TR 27, TR 28, NGC 6416, NGC 6425". Astronomy and Astrophysics. 5: 298. Bibcode:1970A&A.....5..298T.
  6. Feinstein, Carlos; Baume, Gustavo; Vazquez, Ruben; Niemela, Virpi; Cerruti, Miguel Angel (2000). "The Highly Polarized Open Cluster Trumpler 27". The Astronomical Journal. 120 (4): 1906. arXiv:astro-ph/0007093. Bibcode:2000AJ....120.1906F. doi:10.1086/301562.
  7. Massey, Philip; Degioia-Eastwood, Kathleen; Waterhouse, Elizabeth (2001). "The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turnoffs. II. Results from 12 Galactic Clusters and OB Associations". The Astronomical Journal. 121 (2): 1050. arXiv:astro-ph/0010654. Bibcode:2001AJ....121.1050M. doi:10.1086/318769.
  8. "HD 159378". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-31.
  9. Bakker, R.; The, P. S. (1983). "An investigation of the heavily reddened young open cluster TR 27 on the Walraven photometric system". Astronomy and Astrophysics Supplement Series. 52: 27. Bibcode:1983A&AS...52...27B.
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