Corona Australis, a southern constellation

 
Corona Australis, a southern constellation

Image Credit & Copyright: Warren A. Keller, Billions and Billions Fine Art Astrophotography (http://billionsandbillions.com/default.htm)

Corona Australis (also known as CrA and the Southern Crown) is a small, southern constellation, bordered by Sagittarius to the north, Scorpius to the west, Telescopium to the south, and Ara to the southwest. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and the southern counterpart of Corona Borealis, the Northern Crown.

While not a bright constellation, Corona Australis is nonetheless distinctive due to its easily identifiable pattern of stars, which has been described as horseshoe-or oval-shaped. Though it has no stars brighter than magnitude 2.4, it still has 21 stars visible to the unaided eye (brighter than magnitude 5.5), making it the second-brightest constellation.

In this image, the focal point is a gorgeous group of blue reflection nebulae, called NGC 6726/6727 (the upper blue nebula, around an optical double star which are separable with the naked eye and are both white), NGC 6729 (the small white cloud that contains the irregular variable star R CrA which varies in brightness along with its surrounding nebula, just to the left of it), and IC 4812 (the second upper blue nebula), which is associated with hot, young stars, and is home to the double star BSO 14.

The main nebula complex is flanked by the dark nebula Bernes 157 (after the Swedish astronomer, Claes Bernes), which is harbouring star forming regions (though mostly obscured), various Herbig-Haro objects and water molecules. Bernes 157 stretches through several light-years and contains fifty solar masses of molecular gas. It is part of the Corona Australis Molecular Cloud, a star-forming region of around 7000 Solar masses. About 430 light years away, it is one of the closest star-forming regions to our Solar System.

Finally, at 3 o’clock, you can see a magnificent globular star cluster of some 65 light-years across, designated NGC 6723. Though it appears to be part of the group, it is actually located in the neighboring constellation of Sagittarius. The ancient stars of NGC 6723 lie only about 28,400 light-years away from Earth, as compared with the nebulosity, which is about 430 light-years away.

Corona Australis has two known meteor showers. The Corona Australids are a meteor shower that takes place between 14 and 18 March each year, peaking around 16 March. This meteor shower does not have a high peak hourly rate, and its rate varies from year to year. At only five days, the shower’s duration is particularly short, and its meteoroids are small; the stream is devoid of large meteoroids. In 2006, a shower originating near Beta Coronae Australis was designated as the Beta Coronae Australids, and appears in May.

This image was taken in 2013 in Bathurst, NSW-AU, with a SBIG STL-11000M camera on a Takahashi FSQ-106ED telescope, using an Astrodon Generation 1 filter and processed with PixInsight and Photoshop CS6.

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