Cygnus OB2
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| Cygnus OB2 | |
|---|---|
Cygnus OB2 in the light of H-Alpha; 2.5° view
Credit: IPHAS |
|
| Observation data (J2000.0 epoch) | |
| Constellation | Cygnus |
| Right ascension | 20h 33m 12s[1] |
| Declination | 41° 19′ 00″ |
| Distance | 4.7 kly (1400 pc[2]) |
| Apparent magnitude (V) | 6.1 |
| Apparent dimensions (V) | 60.0′ |
| Physical characteristics | |
| Estimated age | 1 to 7 million years |
| Notable features | - |
Cygnus OB2 is an OB association that is home to some of the most massive and most luminous stars known, including suspected LBV 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 1,400 parsecs from Earth in the constellation of Cygnus.[2]
The young cluster is one of the largest known and the largest in the northern hemisphere with some authors formally classifying it as a young globular cluster similar to those in the Large Magellanic Cloud.[4] Today, however, it is considered a massive, low-density stellar association.[5]
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[6] to 100[4] of spectral type O and its total mass having been calculated as (4-10)*104[4] or 3*104 solar masses according to other investigations.[6]
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.
| Star[7] | Schulte number[7] | Spectral type[8] | Bolometric magnitude[8] | Mass[8] (× solar) |
|---|---|---|---|---|
| 59 | #1 | O8.5V | −9.3 | 44 |
| 83[9] | #2 | B1I | −7.4 | 18 |
| #3 | O6IV + O9III | >17 + >8 | ||
| 217 | #4 | O7III((f)) | −9.6 | 52 |
| V729[10][11] | #5 | O7Ianfp + Ofpe/WN9 (+BoV:) | −10.6 / −10.5 | 31 + 9 |
| 317 | #6 | O8V | −9.2 | 42 |
| 457 | #7 | O3If | −10.8 | 114 |
| 465[12] | #8A | O6If + O5.5III(f) | −9.8/−9.4 | 44 + 37 |
| 462 | #8B | O6.5III(f) | −10.4 | 80 |
| 483 | #8C | O5If | −10.1 | 71 |
| 473[13] | #8D | O8.5V + O9V: (+ A2V?) | −8.4 | 19+19+? |
| 431[11][14] | #9 | O5-5.5I + O3-4III | ~−10/~−10 | >34 + >30 |
| 457 | #10 | O9.5I | −10.4 | 75 |
| 734[9] | #11 | O5If | −10.0 | 58 |
| 304[15] | #12 | B3-4Ia+ | −10.95 | 110 |
| 556 | #18 | B1Ib | −9.0 | 33 |
| 417 | #22 | O3If + O6V(f) | ~−10.4 | |
| 516[9] (possible binary[16]) | O5.5V((f)) | −11.1 | 100 | |
| 771 | O7V | −10.6 | 90 |
Other noteworthy stars, not included in the Massey et al. paper include BD+40° 4210, a blue supergiant and luminous blue variable candidate, as well as the massive runaway star BD+43° 3654.
References
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