Cygnus OB2 is an
OB association that is home to some of the
most massive and
most luminous stars
This is a list of stars arranged by their absolute magnitude – their intrinsic stellar luminosity. This cannot be observed directly, so instead must be calculated from the apparent magnitude (the brightness as seen from Earth), the distance t ...
known, including suspected
Luminous blue variable Cyg OB2 #12. It also includes one of the
largest known stars,
NML Cygni.
The region is embedded within a wider one of star formation known as
Cygnus X Cygnus X may refer to:
* Cygnus-X (star complex), a giant star formation region
* Cygnus X (music group)
See also
* Cygnus X-1 (disambiguation)
* Cygnus X-3
Cygnus X-3 is a high-mass X-ray binary ( HMXB), one of the stronger binary ...
, 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.
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
A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...
similar to those in the
Large Magellanic Cloud.
Today, however, it is considered a massive, low-density stellar association.
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
In astronomy, the Great Rift (sometimes called the Dark Rift or less commonly the Dark River) is a dark band caused by interstellar clouds of cosmic dust that significantly obscure ( extinguish) the center and most radial sectors of the Milky ...
, 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
to 100
of
spectral type O and its total mass having been calculated as (4–10)
or 3
solar masses according to other investigations.
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
The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 1 ...
,
Spitzer Space Telescope, the
Herschel Space Observatory and the
Gran Telescopio Canarias
The Gran Telescopio Canarias (GranTeCan or GTC) is a reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain. It is the world's largest single-aperture optical telescope.
Constr ...
. 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.
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.
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]
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.
A 12th star (
Cyg OB2 #12) was added in 1954,
and eight more shortly after.
Schulte himself maintained the already-published numbers and added many more when studying the association which he called VI Cygni.
References
{{Cygnus (constellation)
Stellar associations
Articles containing video clips
Cygnus (constellation)
Star-forming regions