Cygnus OB2

For technical reasons, "Cygnus OB2 #8A" redirects here. For this star, see Cygnus OB2-8A.
For technical reasons, "Cygnus OB2 #12" redirects here. For this star, see Cygnus OB2-12.
Cygnus OB2
Cygnus OB2 in the light of H-Alpha; 3.5° view
Credit: IPHAS
Observation data (J2000.0 epoch)
Right ascension20h 33m 12s[1]
Declination41° 19′ 00″
Distance5.12 kly (1,570+80
−70 pc[2])
Apparent magnitude (V)6.1
Apparent dimensions (V)60.0′
Physical characteristics
Estimated age1 to 7 million years
–
Associations
ConstellationCygnus
See also: Open cluster, List of open clusters
Short narrated video about Cygnus OB2 #9

Cygnus OB2 is an OB association that is home to some of the most massive and most luminous stars known, including suspected Luminous blue variable Cyg OB2 #12. It also includes one of the largest known stars, NML Cygni.[3] The region is embedded within a wider one of star formation known as Cygnus X, which is one of the most luminous objects in the sky at radio wavelengths. The region is approximately 1,570 parsecs from Earth in the constellation of Cygnus.[4]

The young cluster is one of the largest known and the largest in the northern hemisphere with some authors formerly classifying it as a young globular cluster similar to those in the Large Magellanic Cloud.[5] Today, however, it is considered a massive, low-density stellar association.[6]

Although it is over ten times more massive than the Orion Nebula, which is easily seen with the naked eye, Cygnus OB2 is hidden behind a massive dust cloud known as the Cygnus Rift, which obscures many of the stars in it. This means that despite its large size, it is hard to determine its actual properties. The estimated number of massive stars range from 50[7] to 100[5] of spectral type O and its total mass having been calculated as (4–10)×104[5] or 3×104 solar masses according to other investigations.[7]

Despite this, recent surveys ranging from radio to X-ray wavelengths have observed the region to great depths to gain a better understanding of how the processes of star and planet formation occur on such a large scale. These studies include observations with the Chandra X-ray Observatory, Spitzer Space Telescope, the Herschel Space Observatory and the Gran Telescopio Canarias. As for recent observations, the final stages of the process of photoablation is taking place, where the biggest stars formed and cleared the ambient material from the region.[8]

Prominent stars
Schulte number[9] MT number[9] Other name/CPR number[10] Spectral type[10][11] Luminosity[10]
(L☉) 		Mass[10][11]
(M☉)
HD 195213[12] O7 180,300 43.3
WR 144 WC4 158,500 9.9
WR 145 WN7o/CE+O7V((f)) 371,000 18.3
WR 146 WC6+O8III 115,000 8?+?
WR 147[13] WN8h+B0.5V 2,000,000 51
NML Cyg[14][15][16] M4.5–M7.9Ia–III 229,000 50
V1827 Cyg/B17[12] Ofpe 242,100 57
BD+40°4210[12][17] B1III:e 630,000 54
BD+40 4223[12] B0Ia 539,500 48.3
#1 59 O8.5V 120,000 26
#2 83[18] B1I 40,000 14
#3 O6IV+O9III 346,000 >17 + >8
#4 217 O7III((f)) 158,000 29
#5 V729[19][20] O7I+O6I+O9V 1584000 31 + 27 + 9
#6 317 O8V 109,000 25
#7 457 O3If 426,000 47
#8A 465[21] O6If+O5.5III(f) 501,000 44 + 37
#8B 462 O6.5III(f) 301,000 35
#8C 483 O5If 371,000 42
#8D 473[22] O8.5V 48,000 20
#9 431[20][23] O5–5.5I+O3–4III 707,000 >34 + >30
#10 632 O9.5I 478,000 37
#11 734[18] O5If 537,000 44
#12 304[24] B3-4Ia+ 1,230,000 110
#14 227 O9V 45,000 19
#15 258 O8V 61,000 22
#16 299 O8V 83,000 23
#17 339 O8.5V 61,000 21
#18 556 B1Ib 338,000 29
#19 601 B0Iab 186,000 26
#20 145 O9III 26,000 17
#21 259 B0.5V 15,000 13
#22 417 O3If+O6V(f) 660,000 50
#23 470 O9.5V 26,000 17
#24 480 O7.5V 104,000 25
#25 531 O8.5V 97,000 24
#26 642 B1III 69,000 16
#27 696 O9.5V+B0V 30,000 17
#29 745 O7V 87,000 25
#30 793 B1.5III 33,000 13
#37 358 B3V 3,000 7
#41 378 B0V 44,000 18
#51 425 B0V 27,000 16
#54 395 B1V 7,000 10
#64 488 B2Ve 23,000 12
#66 515 B1V 10,000 11
#70 588 B0V 48,000 18
#71 646 B1.5V 6,000 9
#73 O8III+O8III 41,000 20
#74 555 O8V 109,000 25
#75 736 O9V 31,000 18
138[12] O8I 88,700 26
267 A11[12] O7.5III 323,000 35
448 O6V 107,000 29
516[18] O5.5V((f)) 707,000 52
716 O9V 28,000 18
771 O7V 151,000 29
A12[12] B0Ia 373,300 36
A15 O7I 263,000 32
A20 O8II 380,000 35
A23 B0.7Ib 263,000 26
A24 O6.5III 154,000 30
A25[12] O8III 88,700 28
A27 B0Ia 426,000 35
A29[12] O9.7Iab 167,500 29.1
A32[12] O9.5IV 106,700 26.1
A36 B0Ib+B0III 173,000 26
A37[12] O5V((f)) 66,100 34.8
A46[12] O7V((f)) 46,600 25.6
E47 B0Ia 676,000 42
IRAS 20321+4009[12] O9 278,000 32
TYC 3156-998-1[12] OC9.7Ia 516,000 34.2

The progenitor of BD+43°3654 might have been a member of Cygnus OB2. Two stars from two binaries would have collided and merged forming BD+43°3654, which would have then been ejected from the stellar association along with the two remaining stars.[25]

Prominent members of the association are often referred to by their Schulte numbers: for example Schulte 12, VI Cygni 12, or Cygnus OB2 #12. The numbers were first used in the 1953 discovery paper where 11 "blue giants" were numbered.[26] A 12th star (Cyg OB2 #12) was added in 1954,[27] and eight more shortly after.[28] Schulte himself maintained the already-published numbers and added many more when studying the association which he called VI Cygni.[9]

Cygnus OB2 contains embedded star clusters as well as two open clusters located in the center of Cygnus OB2. The open clusters are called Bica 1 and Bica 2. Both Bica 1 and Bica 2 contain several OB-stars, such as Cygnus OB2 #8A and Cygnus OB2 #22.[29]

Open cluster Bica 1
Part of open cluster Bica 2
  1. ^ "Ass Cyg OB 2". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-12-06.
  2. ^ Parker, Richard J.; Crowther, Paul A.; Rate, Gemma (2020). "Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – II. Cluster and association membership". Monthly Notices of the Royal Astronomical Society. 495 (1): 1209–1226. arXiv:2005.02533. Bibcode:2020MNRAS.495.1209R. doi:10.1093/mnras/staa1290. S2CID 218516882.
  3. ^ Schuster, M. T.; Marengo, M.; Hora, J. L.; Fazio, G. G.; Humphreys, R. M.; Gehrz, R. D.; Hinz, P. M.; Kenworthy, M. A.; Hoffmann, W. F. (2009). "Imaging the Cool Hypergiant NML Cygni's Dusty Circumstellar Envelope with Adaptive Optics". The Astrophysical Journal. 699 (2): 1423–1432. arXiv:0904.4690. Bibcode:2009ApJ...699.1423S. doi:10.1088/0004-637X/699/2/1423. S2CID 17699562.
  4. ^ Rygl, K.; Brunthaler, A.; Sanna, A.; Menten, K. M.; Reid, M. J.; van Langevelde, H. J.; Honma, M.; Torstensson, K. J. E.; Fujisawa, K. (March 2012). "Parallaxes and proper motions of interstellar masers toward the Cygnus X star-forming complex. I. Membership of the Cygnus X region". Astronomy and Astrophysics. 539: A79. arXiv:1111.7023. Bibcode:2012A&A...539A..79R. doi:10.1051/0004-6361/201118211. S2CID 54647474.
  5. ^ a b c Knödlseder, J. (2000). "Cygnus OB2—a young globular cluster in the Milky Way". Astronomy and Astrophysics. 360: 539. arXiv:astro-ph/0007442. Bibcode:2000A&A...360..539K.
  6. ^ Wright, Nicholas J.; Parker, Richard J.; Goodwin, Simon P.; Drake, Jeremy J. (2014). "Constraints on massive star formation: Cygnus OB2 was always an association". Monthly Notices of the Royal Astronomical Society. 438 (1): 639–646. arXiv:1311.4537. Bibcode:2014MNRAS.438..639W. doi:10.1093/mnras/stt2232. S2CID 16957082.
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  11. ^ a b Massey, P.; Degioia-Eastwood, K.; Waterhouse, E. (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): 1050–1070. arXiv:astro-ph/0010654. Bibcode:2001AJ....121.1050M. doi:10.1086/318769. S2CID 53345173.
  12. ^ a b c d e f g h i j k l m n Comerón, F.; Pasquali, A. (2012). "New members of the massive stellar population in Cygnus". Astronomy & Astrophysics. 110: 2715. Bibcode:2012A&A...543A.101C. doi:10.1051/0004-6361/201219022.
  13. ^ Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625. arXiv:1904.04687. Bibcode:2019A&A...625A..57H. doi:10.1051/0004-6361/201834850. S2CID 104292503.
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  15. ^ Davies, Ben; Beasor, Emma R. (March 2020). "The 'red supergiant problem': the upper luminosity boundary of Type II supernova progenitors". MNRAS. 493 (1): 468–476. arXiv:2001.06020. Bibcode:2020MNRAS.493..468D. doi:10.1093/mnras/staa174. S2CID 210714093.
  16. ^ Morris, M.; Jura, M. (1983). "The nature of NML Cygnus". Astrophysical Journal. 267: 179. Bibcode:1983ApJ...267..179M. doi:10.1086/160856.
  17. ^ http://www.sciops.esa.int/SD/ESACFACULTY/docs/seminars/160212_Comeron.pdf Archived 2016-03-03 at the Wayback Machine In and around the rich association Cygnus OB2
  18. ^ a b c Herrero, A.; Puls, J.; Najarro, F. (2002). "Fundamental parameters of Galactic luminous OB stars VI. Temperatures, masses and WLR of Cyg OB2 supergiants". Astronomy and Astrophysics. 396 (3): 949–966. arXiv:astro-ph/0210469. Bibcode:2002A&A...396..949H. doi:10.1051/0004-6361:20021432. S2CID 16917437.
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  21. ^ De Becker, M.; Rauw, G.; Sana, H.; Pollock, A. M. T.; Pittard, J. M.; Blomme, R.; Stevens, I. R.; Van Loo, S. (2006). "XMM-Newton observations of the massive colliding wind binary and non-thermal radio emitter CygOB2#8A [O6If + O5.5III(f)]" (PDF). Monthly Notices of the Royal Astronomical Society. 371 (3): 1280–1294. Bibcode:2006MNRAS.371.1280D. doi:10.1111/j.1365-2966.2006.10746.x.
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  23. ^ Nazé, Y.; Mahy, L.; Damerdji, Y.; Kobulnicky, H. A.; Pittard, J. M.; Parkin, E. R.; Absil, O.; Blomme, R. (2012). "The 2.35 year itch of Cygnus OB2 #9". Astronomy & Astrophysics. 546: A37. arXiv:1209.5622. Bibcode:2012A&A...546A..37N. doi:10.1051/0004-6361/201219442. S2CID 119187102.
  24. ^ Clark, J. S.; Najarro, F.; Negueruela, I.; Ritchie, B. W.; Urbaneja, M. A.; Howarth, I. D. (2012). "On the nature of the galactic early-B hypergiants". Astronomy & Astrophysics. 541: A145. arXiv:1202.3991. Bibcode:2012A&A...541A.145C. doi:10.1051/0004-6361/201117472. S2CID 11978733.
  25. ^ Gvaramadze, V. V.; Bomans, D. J. (2008). "BD+43 3654 - a blue straggler?". Astronomy & Astrophysics. 485 (3): L29–L32. arXiv:0805.3893. Bibcode:2008A&A...485L..29G. doi:10.1051/0004-6361:200809860. S2CID 18755032.
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  29. ^ Bica, E.; Bonatto, Ch.; Dutra, C. M. (2003-07-01). "Does Cyg OB2 harbour any open cluster?". Astronomy and Astrophysics. 405 (3): 991–998. Bibcode:2003A&A...405..991B. doi:10.1051/0004-6361:20030700. hdl:10183/108028. ISSN 0004-6361.