The Corona Australis constellation is a small constellation located in the southern celestial hemisphere. Its name comes from Latin, and it translates to “the southern crown”, being the southern counterpart of Corona Borealis, the northern crown.
Key Facts & Summary
- Corona Australis was among the first 48 constellations listed by the famous Greek-Roman astronomer, Ptolemy, in his 2nd century Almagest.
- In our era, Corona Australis is part of the 88 modern constellations, being the 80th largest constellation in the sky, stretching for around 128 square degrees.
- Corona Australis, the southern crown, is smaller, and fainter, than Corona Borealis, the northern crown.
- Corona Australis doesn’t host any Messier Objects, and it has only one meteor shower associated with it, the Corona Australids.
- The brightest star in this constellation is Meridiana / Alpha Coronae Australis, which has an apparent magnitude of 4.102.
- Meridiana is an A-type star, similar to Vega ( Alpha Lyrae – located in the constellation of Lyra).
- Currently, only two stars in Corona Australis have been confirmed to host exoplanets around them.
- There are many interesting stars located in Corona Australis, even though none of them are brighter than magnitude 3.00. Some of these stars are Alpha (Meridiana) and Beta Coronae Australis, which are the two brightest stars, Epsilon Coronae Australis, which is the brightest example of a W Ursae Majoris variable in the southern sky, the variable stars R and TY Coronae Australis, or Zeta and Gamma Coronae Borealis.
- Since Corona Australis lies alongside the Milky Way, it contains many eye-catching deep-sky objects, such as the dark nebula, known as the Corona Australis Molecular Cloud, which is among the closest star-forming regions to our Solar System, the reflection nebula NGC 6729, the Coronet Cluster, or the globular clusters NGC 6723, and NGC 6541, among many others.
Corona Australis Constellation
The constellation of Corona Australis is among the smallest constellations in the sky. Its name comes from Latin, and it translates to “the southern crown”, being the southern counterpart of Corona Borealis, the northern crown, which is brighter, and larger.
Corona Australis isn’t associated with any myths, and it usually represents the crown worn by the celestial centaur, represented by the zodiacal constellation of Sagittarius.
This constellation is also called Corona Austrina. The ancient Greeks viewed Corona Australis as a wreath rather than a crown. Other cultures associated this constellation with a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax.
The constellation of Corona Australis is located in the southern celestial hemisphere. Corona Australis spreads for around 128 square degrees, being the 80th largest constellation in the sky.
Corona Australis lies in the third quadrant of the southern hemisphere (SQ3), and it can be seen at latitudes between +40o and -90o.
- Right Ascension: 17h 58m 30.1113s
- Declination: -36.7785645o – 45.5163460o
- Visible: Between +40o and -90o
- Best Viewed: at 21:00 (9 p.m.) during August
The constellations surrounding Corona Australis are Ara, Sagittarius, Scorpius, and Telescopium. Corona Australis is part of the Hercules family of constellations, along with Aquila, Ara, Centaurus, Corvus, Crux, Cygnus, Hercules, Hydra, Lupus, Lyra, Ophiuchus, Sagitta, Scutum, Sextans, Serpens, Triangulum Australe, and Vulpecula.
Notable Stars in the Constellation of Corona Australis
There are many interesting stars located in Corona Australis, even though none of them are brighter than magnitude 3.00. Some of these stars are Alpha (Meridiana) and Beta Coronae Australis, which are the two brightest stars, Epsilon Coronae Australis, which is the brightest example of a W Ursae Majoris variable in the southern sky, the variable stars R and TY Coronae Australis, or Zeta and Gamma Coronae Borealis.
The brightest star in Corona Australis is Meridiana / Alpha Coronae Australis, which has an apparent magnitude of 4.102. Meridiana is an A-type star, similar to Vega / Alpha Lyrae which is the brightest star in the constellation of Lyra.
Meridiana, designated as Alpha Coronae Australis, or Alphekka Meridiana, is an A-type star located at around 125 light-years away from our Solar System.
It is a fast-spinning star, having a rotational velocity of 195 km / 121 mi per second. It is the brightest star in Corona Australis, having an apparent magnitude of 4.102, and an absolute magnitude of 1.11.
Meridiana is 31 times brighter than our Sun, having 230% of its mass, and radius, thus it is around five times bigger than our Sun. Meridiana is also hotter than our Sun, having temperatures of around 9,100 K, thus it is 50% hotter than our Sun.
This star is close to its breakup velocity, showing excess infrared radiation, which indicates the presence of a ring of dust and gas around it, most likely caused by its rotational velocity.
Beta Coronae Australis
Beta Coronae Australis is the second-brightest star in Corona Australis, having an apparent magnitude of 4.10. It is a faint orange-hued aging K-type giant star, located at around 470 light-years from Earth.
Beta Coronae Australis has an anomaly abundance of CN in its spectrum, and the star has also exhausted its hydrogen supplies. Due to its current evolutional stage, it has expanded its radius several times.
This star now has 4,107% of our Sun’s radius, and it is 693.5 times brighter than our Sun. It is thus, around 80 times bigger than our Sun, yet cooler, having temperatures of around 4,771 K.
Gamma Coronae Australis
Gamma Coronae Australis is a binary star system, being the third brightest object in Corona Australis. It is located at around 56.4 light-years from us, having an apparent magnitude of 4.20, and it is part of the Milky Way’s thin disk.
The two stars in this system are almost identical F-type main-sequence stars, and they are designated as Gamma Coronae Australis A and Gamma Coronae Australis B.
Gamma Coronae Australis A is the primary star, having 115% of our Sun’s mass, 147% of its radius, and temperatures of around 6,090 K. Both stars are almost three times bigger than our Sun.
Gamma Coronae Australis B is slightly smaller than the primary star, having 114% of our Sun’s mass, 142% of its radius, while it is also slightly hotter than the primary star, having temperatures of around 6,100 K. Both stars are hotter than our Sun.
Epsilon Coronae Australis
Epsilon Coronae Australis, also designated as HR 7152, or HD 175813, is an F4V dwarf star located at around 98.4 light-years away from us.
This star is the brightest W Ursae Majoris variable-type of star in the sky, having an apparent magnitude of +4.75, that varies to magnitude 5, within 14 hours.
It has a smaller companion that is situated within its Roche Limit. Epsilon Coronae Australis has 190% of our Sun’s mass, 216% of its radius, and it is hotter than our Sun, having temperatures of around 6,481 K. This star is also a fast spinner, having a rotational velocity of 148.5 km / 92.2 mi per second.
Eta1 and Eta2 Coronae Australis
Eta1 Coronae Australis is a suspected astrometric binary star, located at around 317 light-years away from us. It is an A-type main-sequence star that has an apparent magnitude of 5.456.
This star has around 220% of our Sun’s radius, being 57.72 times brighter, and it is also hotter than our Sun, with temperatures reaching 8,371 K. Eta1 Coronae Australis is also a fast-spinning star, having a rotational velocity of 122.3 km / 75.9 mi per second.
Eta2 Coronae Australis is a B-type subgiant star located at around 790 light-years away from us. It has an apparent magnitude of 5.587, being visible to the naked eye.
Eta2 Coronae Australis has 323% of our Sun’s mass, and it is 171 times brighter than our Sun. It has a rotational velocity of 30 km / 18.6 mi per second, and it is twice as hot as our Sun, having temperatures of around 10,940 K.
Zeta Coronae Australis
Zeta Coronae Australis is a B-type blue-white hued main-sequence star, located at around 193 light-years away from us. It has an apparent magnitude of +4.75 and an absolute magnitude of +0.76.
Zeta Coronae Australis has broad-spectrum absorption lines associated with its rapid rotation, as it has a rotational velocity of 308 km / 191.3 mi per second.
Due to its speed, the star is enveloped by a circumstellar disk of gas and dust, that has a temperature of 120 K, and stretches for 34 AU. This star has 292% of our Sun’s mass, 211% of its radius, and it is 51 times brighter than our Sun.
Zeta Coronae Australis is around four times bigger than our Sun, and it is more than twice as hot, having temperatures of around 12,039 K. This star is very young, being only 76 million years old.
Theta Coronae Australis
Theta Coronae Australis, also known as HR 6951, or HD 170845, is a giant G-type star, located at around 560 light-years away from us. It has an apparent magnitude of 4.64, and an absolute magnitude of -1.54.
Theta Coronae Australis has around 1,100% of our Sun’s radius, being 22 times bigger than our Sun, and it is also 497 times brighter. It has a usually high rotation rate for a giant star, estimated at 11.8 km / 7.3 mi per second. One possible explanation is that this star engulfed a giant planet, such as a hot Jupiter.
RX J1856.5-3754 is a neutron star, part of the Magnificent Seven group of neutron stars that are within 400 and 1,600 light-years away from Earth.
It has an apparent magnitude of 25.6, and it is estimated to be 1 million years old. RX J1856.5-3754 has 90% of our Sun’s mass and a radius between 19 to 41 km / 11.8 to 25.4 mi. This star moves through space with a speed of around 108 km / 67.1 mi per second.
R Coronae Australis
R Coronae Australis is a variable binary star system located at around 310 light-years away from us. It has a combined apparent magnitude of +11.91.
A small reflection nebula, designated as NGC 6729, extends from this star. Little is known about the stars near this nebula. The primary star is estimated to have around 350% of our Sun’s mass.
Deep-Sky Objects in the Constellation of Corona Australis
Corona Australis lies alongside the Milky Way, and it contains many interesting deep-sky objects, such as the dark nebula, known as the Corona Australis Molecular Cloud, which is among the closest star-forming regions to our Solar System, the reflection nebula NGC 6729, the Coronet Cluster, or the globular clusters NGC 6723, and NGC 6541, among many others. Corona Australis doesn’t have any Messier objects.
Corona Australis Nebula
The Corona Australis Nebula is a bright reflection nebula, located at around 420 light-years away from us. This nebula is formed by several bright stars that are caught up in a dark cloud of dust, and this cloud is also a star-forming region, with clusters of young stars embedded within it.
This nebula consists of three regions designated as NGC 6726, NGC 6727, and NGC 6729. The molecular cloud complex in the region is among the nearest areas with recent or ongoing intermediate and low-mass star formation to us.
NGC 6541, also designated as Caldwell 78, is a globular cluster located at around 20,000 light-years away from us. It has an apparent magnitude of 6.3, and it is estimated to be 12.9 billion years old.
NGC 6729, also known as Caldwell 68, is a reflection/emission nebula located at around 130 parsecs away from us. It is among the nearest star-forming regions.
The nebula is 7.5 degrees away from Zeta Corona Australis, and it lies between R Coronae Australis and T Coronae Australis.
The Coronet Cluster, also known as R CrA, after its best-known member, R Coronae Australis, is a small open cluster located at around 550 light-years away from us.
It has an apparent magnitude of 8, and it stretches for around 26 arcminutes. The Coronet Cluster has an estimated age between 0.5 to 2 million years, and it has a radius of around 2.1 light-years. It lies close to the edge of the Gould Belt.
Meteor Showers Associated with the Constellation of Corona Australis
There is only one meteor shower associated with the constellation of Corona Australis, the Corona Australids.
The Corona Australids meteor shower takes place between 14 and 18 March every year, peaking around 16 March. The meteor shower rate varier from year to year, with some showers having 4, while others around 45 meteors peaking per hour.
Did you know?
- The constellation of Corona Australis may have been recorded by the ancient Mesopotamians in the MUL.APIN, as a constellation called MA.GUR – the Bark.
- In the 3rd century BC, the Greek didactic poet, Aratus, wrote about Corona Australis, however, he did not name the constellation.
- Corona Australis is sometimes associated with the myth of Bacchus and Stimula. Jupiter had impregnated Stimula, causing Juno to become jealous. Juno thus convinced Stimula to ask Jupiter to appear in his full splendor, which the mortal woman could not handle, burning her to a crisp. After Bacchus, Stimula’s unborn child, became an adult and the god of wine, he honored his deceased mother by placing a wreath in the sky.
- In Chinese astronomy, the stars of Corona Australis are located within the Black Tortoise of the North – while the constellation itself is known as the Heavenly Turtle, and during the Western Zhou period, it marked the beginning of winter.
- The indigenous Boorong people of northwestern Victoria saw Corona Australis as “Won” – a boomerang thrown by Totyarguil – represented by the bright star Altair.