Corona Australis (the Southern Crown) is a small, faint constellation in the southern sky, known for its distinctive curved pattern of stars. It is the southern counterpart of Corona Borealis (the Northern Crown), although the two constellations are far apart in the sky. Despite having no stars brighter than fourth magnitude, Corona Australis contains one of the nearest regions of active star formation, where clouds of gas and dust are giving birth to new stars.
Where Is Corona Australis and When Can You See It?
Corona Australis is the 80th-largest of the 88 constellations, covering approximately 128 square degrees. It lies just south of Sagittarius, near the rich star fields of the Milky Way. The constellation is best seen during Southern Hemisphere winter, particularly from June through August. Its curved arrangement of stars resembles a small crown or horseshoe beneath the brighter stars of Sagittarius.
Corona Australis is bordered by Sagittarius, Scorpius, Ara, and Telescopium. It is difficult to observe from northern mid-latitudes because it lies so far south.
Corona Australis in Greek Mythology
Corona Australis was known to ancient Greek astronomers. The poet Aratus described a circlet of stars beneath the forefeet of the celestial Archer, Sagittarius, during the third century BC. The constellation was subsequently included among the 48 constellations cataloged by Ptolemy in the second century AD. Its ancient Greek name, Notios Stephanos, means Southern Crown.
Unlike Corona Borealis, which has a well-established association with Ariadne, Corona Australis has no single universally accepted myth. Some later traditions connected it with a wreath associated with Dionysus, but its principal historical identity was simply the southern crown.
Notable Stars in Corona Australis
Although none of its stars are particularly bright, Corona Australis contains several interesting stellar objects.
Image Credit: Torsten Bronger Alphekka Meridiana (Alpha Coronae Australis) is the constellation’s brightest star, shining at magnitude 4.1. Located approximately 125–130 light-years away, it is a blue-white star more massive and luminous than the Sun. Its name means Southern Alphecca, distinguishing it from Alphecca in Corona Borealis.
- Beta Coronae Australis is an orange giant of approximately magnitude 4.1, situated several hundred light-years away. It is considerably larger and more luminous than the Sun.
- Gamma Coronae Australis is a binary star system about 56 light-years away. Both components are similar yellow-white stars, and their orbital motion can be followed over many decades.
- R Coronae Australis is a young variable star embedded in the constellation’s molecular cloud. Its brightness changes irregularly as surrounding dust and gas obscure our view. The star illuminates nearby nebulosity, making it an important object for studying early stellar development.
A Nearby Neutron Star
Corona Australis also contains RX J1856.5−3754, one of the nearest known isolated neutron stars. Located roughly 400 light-years away, it belongs to a group of nearby neutron stars nicknamed the Magnificent Seven. These objects are studied primarily through their X-ray emission, which provides clues about the extreme conditions inside neutron stars. RX -J1856.5−3754 is far too faint to observe with ordinary amateur telescopes.
Deep-Sky Objects in Corona Australis
Corona Australis Molecular Cloud
The constellation’s most important deep-sky feature is the Corona Australis molecular cloud, a nearby star-forming region approximately 400–500 light-years away. This complex contains dark dust clouds, young stars, and beautiful reflection nebulae illuminated by nearby stellar light.
Among its best-known features are NGC 6729, a fan-shaped reflection nebula associated with R Coronae Australis, and the blue reflection nebulae NGC 6726 and NGC 6727.
The region is also home to the Coronet Cluster, a group of young stellar objects still surrounded by material left over from their formation.
The nearby globular cluster NGC 6723 appears in the same general area of sky but actually belongs to Sagittarius and lies much farther away.
NGC 6541 — A Bright Globular Cluster
NGC 6541 is a globular cluster located approximately 22,000 light-years from Earth. It contains a dense population of ancient stars and shines at around magnitude 6.3, making it a rewarding telescopic object for observers in the Southern Hemisphere. Under dark skies, binoculars can reveal it as a faint, fuzzy patch, while larger telescopes begin to resolve its outer stars.
Other Interesting Objects
Corona Australis also contains IC 1297, a small planetary nebula formed from gas expelled by an aging star, and several dark nebulae that obscure the rich background star fields of the Milky Way. Together, these objects make Corona Australis particularly interesting to astrophotographers, despite the constellation’s modest size and faint stars.
How to Find Corona Australis
To locate Corona Australis, begin with the brighter constellation Sagittarius, recognizable by its Teapot-shaped asterism. Look immediately south of Sagittarius for a small arc of relatively faint stars. This curved pattern forms the Southern Crown.
The constellation is best viewed from southern latitudes on clear winter evenings. Binoculars help reveal its stars, while telescopes and long-exposure photography bring out the surrounding nebulae and star-forming clouds.