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Object description
Sharpless 2-86, NGC 6820 and NGC 6823 - Star Formation and an Open Star Cluster in the Constellation Vulpecula

Object description:

Sharpless 2-86 (also GN 19.43.1) is a very faint H-II emission region covering more than 2 x 1 degrees in the constellation Vulpecula. It is a typical star-forming region, and about 50 massive concentration centers of 15 to 70 solar masses have been observed inside the hydrogen cloud using submillimeter observations, enough mass to allow many more new stars to form. The dark cloud in the core region has the popular name "the snorkel".

In the center of the nebular region is the open star cluster NGC 6823, whose hot blue stars provide the ionization energy to make the hydrogen gas glow red. The stars certainly have an age of only a few million years. The cluster is assigned to class I 3 p n according to Shapley and has about 100 members. The distance to the solar system is estimated to 6 000 lightyears and about its apparent diameter of 12 arcminutes this results in a true diameter of about 50 lightyears. NGC 6823 was discovered by Friedrich Wilhelm Herschel on July 17, 1785.

NGC 6820 is classified as a diffuse nebula, but could also be a supernova remnant or a small reflection nebula. It was discovered long after Herschel on August 8, 1864, by German astronomer Albert Marth, who observed with a 48-inch telescope as William Lassel's observer at Lassel's private observatory in Malta. Marth is a rather unknown name in classical astronomical history, although he is credited as the discoverer of nearly 600 objects in the NGC catalog. In 1882 he participated in the Venus transit expedition to the Cape of Good Hope, and the lunar crater Marth and the Martian crater Marth are named after him. The lunar crater Marth is one of the very rare concentric double craters in Palus Epidemiarum.

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