Nebulae - Glittering Lights - Marco Lorenzi
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The Chamaeleon I Cloud

The Chamaeleon I Cloud

Home to some of the nearest molecular clouds, the constellation of Chamaeleon is filled with many dark nebula complexes. The Chamaeleon I complex is one of three large clouds found in this southern constellation and has an age of 2 million years. The distances of the three main clouds range from 520-580 light years and are also isolated from other major star forming complexes. The Chamaeleon I complex is a site of low mass star formation, which is characterised visually by various reflection nebulae including IC 2631 to the north and the blue nebula Ced 111 and the white reflection nebula Ced 110 to the south. The great obscuring mass of thick brown dust in the region absorbs the blue light of distant stars making them appear much redder than they actually are. This process of interstellar reddening also affects the light of distant galaxies in the line of sight, making them look less blue. Despite the copious amounts of dust, the Chamaeleon I complex is regarded by astronomers to impose only a moderate level of extinction on the background starfield in comparison with other dark nebulae. The Chamaeleon I complex is near the south celestial pole and is situated at the edge of the Scorpius-Centaurus OB association. The cloud is illuminated by massive stars that belong to a subgroup of this OB association. Due to its proximity, the Chamaeleon I complex has been subjected to many searches for young stellar objects by many astronomers including Karl Henize in 1963. Recent surveys in the past two decades have also yielded a large sample of YSO's, including the first X-ray emitting brown dwarf, which was discovered in 1998. Young stellar objects have also been discovered in various infrared surveys of the clouds. The cluster of sources associated with the complex is split into two northern and southern subclusters and the cloud contains 200 known low mass YSO's. Analysis of data predicts that star formation began 3-4 million years ago in the northern half of the cloud and 5-6 million years ago in the southern half. Star formation in the cloud is still ensuing at a declining rate until eventually it will completely cease. Other optically visible signs of star formation in the cloud are represented by small Herbig Haro objects and outflows. The first Herbig Haro objects to be discovered in this complex were found in a survey for Herbig Haro objects in dark clouds by Richard Schwartz in 1977. They include HH 48-9 and HH 50. Due to its tiny size, HH 48 isn't visible in this widefield image but the bright Herbig Haro objects HH 49 and HH 50 are prominently visible in the region between Ced 110 and Ced 111. HH 49/50 are associated with the largest outflow in this complex, a giant outflow with a length of 27 arcminutes (or 6.5 light years) and its source is the protostar Cha-MMS1. Spitzer infrared images of HH 49/50 reveal infrared emission associated with them. This infrared nebula has an incredible shape of a "tornado" formed by a pair of twisting helical filaments. Deep imaging surveys in the past decade have found a total of 30 Herbig Haro objects associated with 20 separate outflows. Also visible in the image is a unique curiosity, a colourful orange nebula below the reflection nebula Ced 111. This is the Chamaeleon Infrared Nebula, a bipolar infrared reflection nebula that also happens to be visible optically. Its bipolar nature is only visible in infrared images as well as its illuminating source. Studies of the nebula have shown it to exhibit a complex geometry consisting of a disk surrounding the central source as well as bipolar lobes tracing two cavities cleared out by ouflow activity. Infrared images reveal the two bipolar lobes to be separated by a dark structure, which is a circumstellar disk around the central source (description provided by Sakib Rasool)

Apo TEC140 (140/f7.2) - FLI Proline 16803 - L (580m) R (90m) G (90m) B (90m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia

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