Corona Australis
What is Corona Australis?
Constellations· Summer evenings · a small arc below Sagittarius. Corona Australis is the southern partner of the Northern Crown. Its fourth-magnitude stars trace a small arc beneath the feet of Sagittarius, beside a dark cloud where stars are still being born.
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Stars of the figure
| Star | Magnitude |
|---|---|
| Alfecca Meridiana | 4.1 |
| Beta Coronae Australis | 4.1 |
The 2 brightest of the 3 stars used in the figure (2 lines). Lower magnitude means brighter.
Constellation basics
| Season | Jul–Aug evenings, near the southern horizon; low from New York, barely clearing the horizon from London |
|---|---|
| Brightest star | α (Meridiana) and β, both mag 4.1 |
| How to find | a small arc right below the Sagittarius Teapot |
| Area rank | 80th of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
The Southern Crown's star names and East Asia's turtle
The alpha star of Corona Australis has the official name Meridiana, approved by the International Astronomical Union in 2017. Traditionally it was called Alfecca Meridiana. The first part, Alfecca, is borrowed from the name of the brightest star in the Northern Crown, and Meridiana means southern. So the two crowns are paired not only in shape but also in their star names.
East Asian skywatchers saw the same stars quite differently. Old Chinese astronomy read this arc not as a crown but as Bie, a soft-shelled turtle. It was pictured as a waterside animal sitting at the edge of the Milky Way, south of Sagittarius. The curve that Europe saw as a round crown, East Asia saw as a round shell.
The pictures differ from culture to culture, but they share something. In each case people read this small curve as one rounded object. Even without bright stars, its stars form an even, curved line, so it stood out clearly as a shape. It is an example of how people looking at the same sky drew pictures that fit their own lives and stories.
The constellation in depth
Corona Australis is a small constellation known since Ptolemy in the 2nd century. It is the partner of the Northern Crown in the northern sky, and in both the stars form a rounded arc. In old stories it is a crown dropped by the centaur of Sagittarius, or a wreath that Dionysus, the god of wine, placed in the sky for his mother Semele.
It has no bright stars, but its neat arc is easy to recognise once seen. The stars in the arc are not close together, though. Alpha is a white star about 125 light-years away, while Beta is an orange giant several times farther off. Stars at very different distances just happen to line up in an arc as seen from Earth.
The constellation contains a dark gas cloud called the Corona Australis molecular cloud. About 430 light-years away, it is one of the closer places where stars are being born. The newborn stars are buried in dust, so they barely show in ordinary light but shine in infrared. Nearby blue reflection nebulae, NGC 6726 and 6729, mark this star-forming region.
Corona Australis can be seen from mid-northern latitudes, low above the southern horizon on July and August nights. Find the Teapot shape made by the stars of Sagittarius and look right below it. You need an open southern view. In the Sky view, set a southern-hemisphere city on an August night to see the whole arc. From northern latitudes, the best time is a summer night when the southern sky is darkest.
Frequently asked
- When can I see Corona Australis?
- Corona Australis is best seen in Jul–Aug evenings, near the southern horizon; low from New York, barely clearing the horizon from London.
- How do I find Corona Australis?
- To find Corona Australis, look for a small arc right below the Sagittarius Teapot.
- What is the brightest star in Corona Australis?
- The brightest star in Corona Australis is Alfecca Meridiana, at magnitude 4.1.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.