Star Forming Region RCW 108 in ARA
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Star Forming Region RCW 108 in ARA

May 19, 2005
The Ara OB1 association contains many young and bright stars (of types O and B; hence the name). It is located at a distance of about 4000 light-years (1.3 kpc) from the Sun; the part shown in PR Photo 21a/99 covers an area of about 40 light-years across (approx. 12 x 12 pc) and includes most of RCW 108 .

RCW 108 is a molecular cloud that is in the process of being destroyed by intense ultraviolet radiation from heavy and hot stars in the nearby stellar cluster NGC 6193 , seen to the left in the photos. Most of this radiation comes from the bright object near the center of the image, which is actually a binary system composed of two O-type stars. The red glow that pervades the field is emission in the red H-alpha spectral line of hydrogen. It reveals a massive stream of gas that flows away from the molecular complex as it is being heated and ionized.

The small bright patch with several stars near the darkest part of the nebulosity, to the right in the photos, is the infrared source IRAS 16362-4845 . It marks a site where a small cluster of stars is being formed at present.

The designation RCW 108 refers to the inclusion of this object in "A catalogue of H-alpha emission regions in the southern Milky Way", published by three astronomers (A.W. Rodgers, C.T. Campbell and J.B. Whiteoak) in 1960.

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