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NGC 2359, "Thors Helmet" -a Wolf Rayet nebulae in the constellation Canis Major

Short object description:NGC 2359 and Haffner 6

NGC 2359, also called "Thor's helmet" because of its outer shape, is an emission nebula in the constellation of Canis Major. It surrounds a massive and with 50.000 degrees Celsius very hot Wolf Rayet star with the designation HD 56925 or WR 7. The star with a brightness of 11.5 magnitude is located a bit west (right in the image) of the center of the bubble. NGC 2359 is located at a distance of about 15,000 light years from the solar system, the central bubble has a diameter of about 20 light years.

Wolf Rayet stars are typically characterized by the repulsion of large amounts of material as so-called violent "stellar winds". The often episodic loss of mass is enormous and when the wind encounters the general interstellar matter in the star's surroundings, a fibre structure is formed - similar to a supernova. The initial masses of young WR stars are between 10 and 250 solar masses.
In later stages WR stars are the exposed cores of formerly massive stars. They are not assigned to any of the usual spectral classes, but are classified in a separate type. Another nebula with WR star in the southern night sky is the bipolar nebula NGC 6164/65 in the constellation Norma.

NGC 2359 was discovered by William Herschel on January 31, 1785 and in 1877 a brighter section was catalogued by Wilhelm Tempel as NGC 2361.

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Haffner 6

Besides the classic star clusters from the Messier, NGC or IC catalogues, there are also special, mostly unknown catalogues like Berkeley, Stock and also Haffner. The star clusters of these catalogs have mostly been catalogued on the basis of photo plate surveys. Hans Haffner (1912 - 1977) was an astronomer at the Hamburg-Bergedorf observatory in the mid-1950s, his catalogue contains 27 objects.

Haffner 6 is strongly concentrated and has a diameter of approx. 5 arc minutes. The brightest stars have the 16th magnitude class, the cluster is classified by Trumpler as type IV 2 r n. The age of the star cluster is approximately 800 million years.

Berkeley 36

Berkeley 36 is an open star cluster with an apparent diameter of 5 arc minutes. It consists of about 40 stars with the brightest stars having only 17th magnitude. Its distance to the solar system is given as 20 000 lightyears.

The Berkeley catalogue includes 104 open star clusters, 88 of which were first discovered and observed on photographic plates by astronomers from the "University of California at Berkeley".

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