Nebulae - Glittering Lights - Marco Lorenzi
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Circinus Star Forming Complex

Circinus Star Forming Complex

Like black ink spilt on a galactic beach, the twisting filamentary tendrils of the dark nebula Sandqvist 169 snake across a glittering field of bright Milky Way stars in the constellation of Circinus. It forms the western part of the giant Circinus Cloud complex, which measures a whopping 2x5 degrees in total! The series of filaments that seemingly emanate outwards from the dense central part of Sandqvist 169 (also known as Circinus-W) are indicative of past violent activity. The filamentary appearance of the cloud is likely to be the result of multiple outflows from young stars, whose formation might have been triggered by a supernova that exploded in close proximity to the cloud. If star formation has ensued for a few hundred thousand years, then the cloud has produced many dozens of young stars, whose outflows have torn the cloud apart. The filaments and cavities provide a fossil record of past star formation as they trace the boundaries of the outflows. Optically visible signs of star formation in Sandqvist 169 include the tiny cometary reflection nebulae vdBH65a and vdBH65b. vdBH65a is a small nebulous patch that is near a bright yellow star that is situated towards the north of the central portion of the cloud. Its illuminating star drives a bipolar molecular outflow that includes the optical bowshock HH 139 (which cannot be seen at a widefield scale). vdBH65b is a small fan shaped cometary reflection nebula that can be seen embedded in the filaments to the right of the cloud core (which are catalogued as Sandqvist 171). It is also the source of numerous Herbig Haro outflows and objects, which are not visible at this scale. Despite its size and apparent interesting past history, the Circinus Cloud has been the subject of very few detailed studies but future investigation and observations will help unravel more of its mysteries. Since it has only received one major study since its discovery, its distance is extremely uncertain and is estimated to be 2275 light years. However, a study in 2011 with observations from the Widefield Infrared Survey Explorer (WISE) telescope uncovered an embedded infrared cluster of YSO's. The Sandqvist catalogue is a collection of 95 southern dark clouds that was published in 1977 by the Swedish astronomer Aage Sandqvist. Confusingly the numbering of the catalogue starts from the number 101 to avoid mix-up with the SL catalogue, which was published by Aage Sandqvist and K.P. Lindroos in the previous year (description provided by Sakib Rasool)

Apo TEC140 (140/f7.2) - FLI Proline 16803 - Ha (690m) L (520m) R (120m) G (120m) B (120m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia