(J. Knödlseder, 2000, A&A, 360, 539)
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(J. Knödlseder, 2000, A&A, 360, 539) |
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| Cygnus OB2 is one of the richest and most heavily reddened OB associations in our Galaxy. The analysis of 2MASS infrared observations in the J, H, and K bands has lead to the discovery of a hugh number of previously unknown massive stars in this association. The stars escaped detection so far owing to considerable visual extinction in this area that is caused by an extended molecular cloud structure known as the Great Cygnus Rift. About 120 O stars and 2600 OB stars have been detected, the largest number ever found in a galactic massive star association. The total mass of Cygnus OB2 is estimated to 40,000 - 100,000 solar masses, rivaling with the weight of small globular clusters. The central mass density amounts to 40 - 150 solar masses per cubic-parsec, a value that is typical for young globulars that are observed in extragalactic systems, such as the Large Magellanic Cloud or in extragalactic star forming regions. Taken together, the mass, density and size of Cygnus OB2 ask for a reclassification of the object as a young globular cluster. This is the first object of this class in the Milky Way. |
| Last update : 5-6-2002 |