NGC 6188 - Fighting Dragons of Ara
In the constellation Ara, south of Scorpius, there is an extraordinary star-forming region in the Milky Way. It is sometimes called the "Rim Nebula" but more often referred to by the fitting name "Fighting Dragons of Ara." This region is one of the most bizarre in the Milky Way. The main objects are easy to find: the central emission nebula with the dark dragon heads is designated NGC 6188, while the relatively inconspicuous star cluster NGC 6193 to the east of the lower dragon head plays a significant role in the formation of the region. NGC 6164/65 ("The Egg" around which the dragons fight) is often classified as a planetary nebula, but it is not one. This bipolar nebula is already in the constellation Norma. NGC 6164 and NGC 6165 refer to the northern and southern core regions of a bipolar nebula, respectively.The outer shell of the nebula glows strongly in the light of ionized oxygen. The central star of the nebula, HD 148937, is likely a very hot multiple system consisting of at least three components. It has 40 times the mass of the Sun. It may be a Wolf-Rayet star, which blows off its outer layers due to strong stellar winds. The inner shell is illuminated by the intense UV radiation of the star, while the outer filaments probably originate from an outburst about 200,000 years ago. HD 148937 is located at a distance of 4200 light-years and could thus belong to the rest of the nebula complex, which is at a similar distance.
The extensive star-forming region NGC 6188 (also known as RCW 108) primarily consists of hydrogen gas. Mainly, two O-type stars in the star cluster NGC 6193, which forms the center of the Ara OB1 star association, are responsible for ionizing the entire nebula and causing the reddish glow in the light of the H-alpha line. The strong radiation, combined with powerful stellar winds, triggers the formation of many new stars in the region. For example, a small nebula can be found to the right of the dark nebula edge between NGC 6188 and NGC 6193: GN-16.36.2.02. Three stars are visible in the H-alpha image, while approximately 40 other massive O and B stars that have just formed are still hidden in the dust clouds.
NGC 6193 formed only 3 million years ago; before that, the molecular cloud complexes were hidden in the dark.
