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Harel Boren | all galleries >> Galleries >> International Acknowledgements - APODs and Publications > The Tulip Nebula Sh2-101, HD226868 (w/Cyg X-1) NGC 6871, B146, B147 1300 pixels
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June 15, 2010 Harel Boren

The Tulip Nebula Sh2-101, HD226868 (w/Cyg X-1) NGC 6871, B146, B147 1300 pixels

Km. 101, East Negev Desert, Israel

Canon XSi, modded, Total 60 min. = RGB 20x3 min. ISO 1600
Boren-Simon 2.8-8 ED OTA - - EQ6 mount, guided w/PHD and EQMOD

The Tulip Nebula, or Sharpless 101 (Sh2-101) is an emission nebula located in the constellation Cygnus, about a 2 degrees southwest of NGC6888, the “Crescent Nebula”, and inside the Orion spiral arm of our galaxy, in which our own solar system lays as well. It was catalogued by astronomer Stewart Sharpless in his 1959 catalog of nebulae. It lies at a distance of about 8,000 light-years (7.6ª1016 km; 4.7ª1016 mi) from Earth.

The Tulip nebula, at least in the field seen from earth, is in close proximity to Cygnus X-1, the brightest source of hard X-rays in our sky, and site of one of the first suspected black holes. This first X-ray source in Cygnus, was discovered by the Giacconi group shortly after their discovery of Sco X-1, and also by a group at the Naval Research Laboratory. Over the years the location of this X-ray source became more accurately determined. The X-ray source was found to lie very close to the position of a 9th magnitude blue star called HD 226868. This was confirmed when a radio flare was detected, at the same time as a jump in the X-ray brightness, and found to be from the same direction.

HDE 226868 is a large blue super giant, and its companion - the more compact of the two objects in the system - is thought to be between 20 and 35 solar masses. Since the largest possible mass of a neutron star can not exceed three solar masses, the compact object which is unseen, is almost certainly a black hole. HDE 226868 (in this image - the bottom star of the bright couple located almost directly to the right of the Tulip) is an O9-B0 supergiant with a surface temperature of 31,000 Kelvin, comprising about 20-40 solar masses. These two objects share an orbital periodicity of 5.6 days.

The matter being stripped off HDE 226868 by the black hole's powerful gravity forms an accretion disk around the black hole, as well as forming an associated wind corona from the blue supergiant. This process results in the plentiful X-ray emissions that were first discovered 30 years ago.

NGC 6871 is an open star cluster, also idenfied as GC 4548, h 2067 and Struve 2630. Its apparent diameter is 20 arc minutes.

Barnard 147 Is a snake-like dark nebula - the left side of which shows well in this image. Barnard 146 is the larger dark area just under and to the right of the cluster NGC 6871 in this image.

The texts above were composed of several sources, including Neil Fleming's site, Wikipedia, and others.

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