|
|
|
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.
« Click here or the thumbnail to load a large annoted image
and a size comparison to the full moon. |
|
|
|
|
|
All Images and all Content are ©
by Franz Hofmann + Wolfgang Paech |