R Coronae Australis Nebula

Part of a complex of reflection and emission nebulae in the northeastern corner of Corona Australis, very close to its border with Sagittarius. These nebulae lie southward of the prominent Milk Dipper formation within Sagittarius, though they are far too faint to be seen with the naked eye. The R Coronae Australis Nebula and its companions are significant as one of the closest star-forming regions to the Solar System, at a distance of some four hundred light years.

In the depths of the dark Corona Australis Molecular Cloud, a group of new stars have formed to fill a patch of the cloud with light. The energy from two of these stars creates a pair of intertwined blue-white clouds swirling with patterns, and these two nebulae, NGC 6726 and NGC 6727, form the backdrop to the R Coronae Australis Nebula.

In the foreground of these broad white nebulae lies the darker elongated shape of the R Coronae Australis Nebula itself, also designated Caldwell 68 or NGC 6729. This is an intricately detailed darker patch centred on a string of nebulous matter that runs from the star R Coronae Australis towards neighbouring T Corona Australis. This corridor of material is illuminated by the light of these two stars and others forming within the region. The surrounding area is filled with darker shapes, most notably an elliptical fan-shaped structure, the results of feathery tendrils of matter being stirred by newborn stars within the nebula.

Both R and T Coronae Australis are variable stars whose brightness can increase or decrease by up to three magnitudes. Because the R Coronae Australis Nebula is lit by these stars, their shifts in magnitude cause the nebula itself to change in brightness in an irregular pattern.