First of all, what is a constellation?
Before we dive into the Corona Australis constellation, first we need to understand exactly what a constellation is.
Basically, it is a group of Stars. A constellation is an area on the celestial sphere (an imaginary sphere) where a group of visible stars are located.
These stars typically form a pattern or outline, which we perceive to represent an inanimate object, (like the Plough or Big Dipper); an animal (like Scorpius a mythical person (like Zeus, Semele and their son Dionysus from Greek mythology) or even a type of creature like Centaurus, the Centaur.
It is also an astronomy term that is often used to describe a variety of groups of stars that have been given a specific name such as – Scorpius, Sagittarius, Orion or Virgo. Constellations are constantly moving and move in the direction from East to West.
The Corona Australis Constellation – Facts in brief:
What is it? –
The Constellation Corona Australis is one of the fainter constellations seen in the Southern Hemisphere. The name ‘Corona Australis’ comes from the Latin language and means ‘the Southern Crown’. It is the southern counterpart of ‘Corona Borealis, which means ‘the Northern Crown’.
The Corona Australis Constellation is quite easy to recognize, if you join the dots and use your imagination. It resembles the outline of a wreath-type crown like the crown on the head of the Centaur that represents the nearby Constellation of Sagittarius.
In the 2nd century AD it was one of the 48 earlier Constellations listed by Ptolemy and is still considered as one of the 88 modern Constellations. It is sometimes called Corona Austrina.
Where is it located? –
The Corona Australis Constellation is positioned in the third quadrant of the Southern Hemisphere, south of the celestial equator. It is sometimes referred to being located in the SQ3 Quadrant.
The neighboring Constellations of Corona Australis includes,
- Sagittarius, Scorpius, Ara and Telescopium.
Where can it be seen?
Co-ordinates of a right ascension, or left ascension and their declination are used to locate all of the Constellations, like Corona Australis.
The bright Stars of Corona Australiscan be more easily observed from the Southern Hemisphere, in the Southern Sky.
Location In the Southern Hemisphere
The Corona Australis Constellation is found at around 17 hours, 58 minutes – 19 hours, 19 minutes right ascension, and a – 36.8 to – 45.5 degree declination in the Southern Celestial Sky.
Visibility from the Southern Hemisphere
It is visible in the Southern Hemisphere at latitudes between +40 degrees and – 90 degrees.
Constellation Corona Australis covers an area of 128 square degrees in the night sky. This makes it the 80th largest Constellation in size.
It is best seen in the southern sky in the summer months, particularly in the month of August.
Visibility from the Northern Hemisphere
The Constellation of Corona Australis is visible from the Northern Hemisphere in August.
At latitudes north of 50 degrees it is located completely below the horizon, this makes it difficult to see from certain parts of the Northern Hemisphere. For example it is not visible from the United Kingdom, but is visible in parts of Southern Europe.
How can you identify Corona Australis?
The simplest method for spotting any particular Constellation from Earth is to first of all locate the brightest star in that Constellation, and then look at the neighboring illuminations, to see if you can identify a recognizable pattern.
It can be spotted if you look towards the southern region of the southern celestial hemisphere night sky, between the Constellation of Sagittarius, the Constellation of Scorpius and the Constellations of Ara and Telescopium.
It is typically represented as the crown (or a horseshoe or wreath shape) in the night sky.
The Stars of Corona Australis
The star system of Corona Australis has:
- Only 1 formally main named Star, ‘Meridiana’, which is approved by the International Astronomical Union (IAU) – and it has a proper name ‘Alphekka Meridiana’, which is Latin for Alphekka South (or Alpecca South).
The brightest star in the Constellation, Meridiana (Alpha Coronae Australis, a CrA), has an apparent visual magnitude of 4.11, and is located around 125 light years from Earth.
The name Alpecca or Alpekka, is from the Arabic language meaning the ‘bright star of the broken ring of stars’
- The second brightest star Beta Coronae Australis has a very similar apparent magnitude to the alpha star so it is sometimes hard to identify which is the brightest Star of the two.
- The dimmest Star that can be seen by the naked eye is known as HD 179433 with an apparent magnitude of 5.91
- 2 Stars with known planets (the better known one is HD 166348 – a K-class Dwarf Star)
- 14 Bayer Flamsteed categorized Stars.
- It has 10 Stars that are known to host exoplanets, (the closest star to Earth with an exoplanet is HD 166724, and located around 138 light years away).
Exoplanets are being discovered all the time so this number could increase.
- There are No Messier objects .
It is the combined light of the various stars in this faint star system that produces enough light to give Meridiana the brightest star status in the Constellation of Corona Australis.
An apparent magnitude of 6.0 is believed to be dimmest level where it is still possible to see a Star by naked eye.
Spotting the Corona Australis in the night sky
The brightest Star, alpha Coronae Australis is one of 6 main stars located in the shape of the crown that is used to spot the Constellation Corona Australis.
This regal crown or ancient Greek wreath shape is sometimes represented as an ostrich nest, a tent or a turtle in other cultures.
This simple technique of trying to make identifiable patterns from the brighter Stars in the night sky can be used to spot other Constellation patterns too like the Goat (Capricornus).
The Location of the Constellation of Corona Australis
The Constellation of Corona Australis belongs to a family of constellations known as the ‘Hercules Family of Constellations’.
The ‘Hercules Family of Constellations” includes Aquila; Ara; Centaurus; Corvus; Crater; Crux; Cygnus; Hercules; Lupus; Lyra; Ophiuchus; Sagitta; Scutum; Sextans; Serpens; Triangulum Australe, and Vulpecula.
FACT: The ecliptic is an imaginary line tracing the route that The Sun, the Moon, and the Planets take across the sky each year. It usually refers to the route that the Earth takes around the Sun and this is the measure that the positions that the Constellations are based upon.
The Celestial Equator is the projection of the terrestrial equator into space.
As the Constellation of Corona Australis is made up of Stars in different locations and from a variety of distances it is not possible to simply go to one location and guarantee to see it.
The different locations of the Stars in the constellation of Corona Australis range from the furthest Star at a distance of almost 558 light years from Earth to the closest Star that is 56.4 light years away.
The closest Star to Earth in this Constellation is known as HIP 89211
The Constellation of Corona Australis is less visible from the Northern Hemisphere as it is located close to the horizon within the Southern Celestial Hemisphere.
The best time to spot it is in August at night, around 21.00
How is it formed and named?
The Constellation of Corona Australis is a small, faint constellation and ranks as the 80th largest in the Southern Celestial Sky out of the 88 listed. Corona Australis fills an area of 128 square degrees in the sky.
It has a simple and easy to identify shape, which we imagine today to represent a big horseshoe or a crown, whereas the ancient Greeks believed it represented a wreath, or a circlet of Stars.
The image is formed by the positions of its main Stars, which form a gently curved shape like a crown.
The 6 main stars forming the shape of the crown from top to bottom are:
- Epsilon Coronae Australis;
- Gamma Coronae Australis;
- Alpha Coronae Australis;
- Beta Coronae Australis;
- Delta Coronae Australis,
- Theta Coronae Australis.
Other close stars within the constellation but not forming the specific outline of the crown shape include:
- Kappa Coronae Australis;
- Lambda Coronae Australis;
- Mu Coronae Australis;
- Zeta Coronae Australis
- Eta Coronae Australis.
The International Astronomical Union (IAU), has defined the boundaries of the Constellation of Corona Australis as having several stars that are visible by the naked eye.
The name of the Constellation Corona Australis is often referred to by the abbreviation ‘CrA’.
The main Stars in Constellation Corona Australis
There are many different Stars within Corona Australis.
The main stars of Corona Australis are categorized by letters of the Greek alphabet, ranging in luminosity from the brightest Star, (the alpha star, the Alfecca Meridiana, also known as Alpha Coronae Australis) then in decreasing order of luminosity through the alphabet.
Corona Australis does not contain any Stars with an apparent magnitude less than 4.0.
(The lower the apparent magnitude value the brighter the Star, therefore with no Stars registering less that 4.0 it means that Corona Australis is one of the fainter Constellations in the southern sky).
- Alfecca Meridiana (Alpha Coronae Australis) the brightest Star in Corona Australis and the only Star with an actual name, meaning ‘the Southern Crown’.
It gets its name from a combination of the Arabic word (Alphekka) meaning ‘break’ as that represents the shape of both constellations Corona Australis and Corona Borealis, and a Latin word (Meridiana) for the ‘Southern’ aspect of the name.
Meridiana is a white main sequence Star located around 130 light years from Earth this supergiant has an apparent magnitude of 4.11. It is 31 times brighter than the Sun.
- Beta Coronae Australis is the second brightest Star in Corona Australis, and is an Orange Giant Star and is located around 510 light years from Earth with a visual magnitude of 4.12 (an apparent magnitude that is almost indistinguishable from the apparent magnitude of 4.11 of the Alpha Star). It is around 80% bigger and 694 times brighter than the Sun, but cooler.
- Gamma Coronae Australis is the third brightest Star and a Binary Star System in Corona Australis, that is a part of the thin disk of the Milky Way. It has a combined visual magnitude of 4.20 and it is located around 56 light years from Earth
- Delta Coronae Australis is an Orange Giant Star in Corona Australis. It has a visual magnitude of 4.58, and it is located around 174 light years from Earth
- Zeta Coronae Australis is a solitary Blue-White Sub dwarf Star in Corona Australis with a visual magnitude of 4.75, and it is located around 193 light years from Earth. This is a young Star that is around 4 times bigger and 2 times hotter than the Sun.
- Theta Coronae Australis is a Yellow giant G type Star in Corona Australis with a visual magnitude of 4.64, and it is located around 558 light years from Earth. It is 22 times bigger and around 497 times brighter than the Sun.
This Star is also known as HD 170845 or HR 6951.
Deep Sky Objects in the Corona Australis Constellation
There are many other objects of interest, although they are not visible to the naked eye, in the Constellation of Corona Australis.
They include Deep Sky Objects such as:
The Corona Australis Nebula
- The Corona Australis Nebula – a bright reflection nebula that is composed of bright Stars, and many young Stars, which are surrounded by dust and gas, and located around 420 light years from Earth.
NGC 6726, NGC 6727 and NGC 6729 are all blue reflection nebulae. Their bright stars are all caught up in in a large cloud of dust that reflects the blue light of the stars. They are located around 400-500 light years from Earth and form the 3 regions of the Corona Australis Nebula.
The Corona Australis Nebula is one of the closest and most active areas for ongoing Star formation that we know about.
The Coronet Cluster
- The Coronet Cluster – an open Star Cluster, also known by the name of one of its best-known members – R Coronae Australis (R CrA) – is a small open cluster at the heart of the Corona Australis region and is surrounded by dust and gas. It contains dozens of young stars at various stages of evolution which is of great research value to astronomers.
It is located around 550 light years from Earth.
Other NGCs in the Constellation include:
- NGC 6729 – (also known as Caldwell 68) is a reflection nebula /emissions nebula that is located close to the star Zeta Sagittarii.
- This reflection nebula is an extension of the Star R Coronae Australis (R CrA), an irregular variable Star System, with a combined apparent magnitude of 11.91 (not visible by the naked eye) and located around 310 light years from Earth.
- NGC 6541 – a global Star Cluster that’s around 129 billion years old. It has an apparent visual magnitude of 7.32 and is located around 20,000 light years from Earth.
- NGC 6496 – a globular cluster with an apparent magnitude of 9.96
How do the Bright Stars of the Corona Australis Constellation shape up?
The Stars of Corona Australis
If you look up and into the night sky you can imagine the recognizable outline of the Constellation of Corona Australis, by the 6 main Stars, which make up the outline of the crown.
Although it is fainter than its neighboring Constellations it has a total of 21 Stars that are visible to the naked eye within the Constellation.
Stars with Planets
Corona Australis has 2 Stars with known Planets, (one is called HD 166724 and is actually a K-class dwarf Star), orbiting around them in the solar system but they are unlikely to be able to support life forms.
Corona Australis has 1 Star with an exoplanet (extrasolar planets), or planets that are outside of the solar system.
Stars without Planets
Corona Australis has further cataloged Stars with no planets.
It also has 14 stellar members with the Bayer Flamsteed designations.
FACT: A Bayer Flamsteed designation for a Star is a combination of a number and the name of the Constellation it can be identified within by the naked eye from England in the United Kingdom.
They are named after John Flamsteed who designed this categorization for listing visible Stars in his ‘History Coelestis Britannica’ catalogue.
When was it first discovered? –
In 1603, Johann Bayer created a celestial atlas called Uranometria and listed the Corona Australis and Corona Borealis Constellations in it.
The ancient Greeks were the first ancient culture to name 88 Constellations in the sky.
The Constellation Corona Australis ranks the 80th largest in area and was one of the first 48 Constellations, named by the Greek astronomer Ptolemy.
They were each given 3-letter abbreviations to help identify them and the Stars within those Constellations are also referred to by those 3-letter codes.
When referring to a Star within a Constellation it is given the Latin genitive form of the Constellation name.
‘Coronae Australis’ is the Latin genitive form of Corona Australis.
FACT: In Latin, the genitive is the case of description.
The named Stars in Corona Australis
Within the Constellation Corona Australis, the Stars would be referred to by: the name or the letter from the Greek Alphabet, in order of brightness followed by ‘Coronae Australis’, (or their proper name) such as:
- Alpha Coronae Australis (Alfecca Meridiana) – is the brightest Star in the Constellation,
FACT: the brighter the luminosity of the star the lower the apparent magnitude number.
What is the purpose of Corona Australis –
In ancient times the dots, bright lights and perceived objects in the sky were of great interest and the makings of folklore to a great range of people from seamen to farmers.
From children to the elderly, we have had an ongoing fascination, with our solar system and star system. Perhaps it’s because the enormity and variety within it makes us realize just how large and exciting the universe is.
FACT: The Star System or Stellar System is a small number of stars that orbit around each other and are bound together by gravity.
When it becomes a large group of stars, again bound together in the same way, by gravity, it is known as a Galaxy or Star Cluster. Whether they contain small groups of stars or larger groups of stars they both come under the classification of ‘Star System’.
The star formations of the Constellations in the night sky were a useful navigation tool and guide as well as the subject of legends and myths, about characters like Zeus, Orion and other powerful gods.
42 of Constellations with their star formations have been named after animals with a story behind each name. Constellations change their positions throughout the year as the Earth rotates around the Sun.
This means our position in space is forever changing and as a result our view of what’s in space changes too, and will continue to do so.
Background & Facts:
The neighbors of Constellation Corona Australis
The Constellation of Corona Australis is neighbored by several constellations in the Southern Sky: and can be used as the guide point for finding the smaller constellation Corona Borealis in the night sky.
This small Constellation of Corona Australis is bordered by –
- Sagittarius – to the Northwest
- Scorpius to the East and Northeast
- Ara to the Southeast
- Telescopium to the Southwest
Within Constellation Corona Australis
The Constellation of Corona Australis is formed by of a number of different components.
The different components housed by the Constellation Corona Australis are mainly Stars, Deep Sky Objects and Galaxies.
The best time of year to see the Stars and Deep Sky Objects in Corona Australis is August.
The sky is home to various bright stars.
The brightness of a star is measured by a value called its magnitude and they come in different sizes, composition, mass and color. Their vast distance away from us is measured in light years from either the Earth or the Sun.
The lower the magnitude value the brighter the star appears in the night sky when viewed from Earth.
FACT: The Sun is considered to be the brightest star in the sky.
There are 2 stars known to host planets within the Constellation Corona Australis that have been officially approved by the International Astronomical Union (IAU):
As well as Stars, the Corona Australis Constellation also has deep sky objects and galaxies, galaxy clusters (or even globular clusters or open clusters), but no Messier objects.
Deep Sky Objects
FACT: A Deep Sky Object is an astronomical object, that is not a solar system object like the Sun, Moon, Comet or a Planet. An individual Star is not considered to be a Deep Sky Object.
Deep Sky Objects are faint objects that can still be observed by the naked eye in the night sky from Earth.
They include Galaxies, Star Clusters and Nebulae.
The most notable Deep Sky objects in the Constellation of Corona Australis are
- the Corona Australis Nebula and the Coronet Cluster.
Meteor showers in the Constellation of Corona Australis
There is one meteor shower associated with the Corona Australis Constellation – ‘The Corona Australid, which is visible in the month of March.
This meteor shower occurs between the days of March 14–18, with its peak on March 16.
Fact: Different galaxies located near the center of the Constellations were discovered and recorded by John Herschel, an English Astronomer, in the 1830s.
Messier Objects and Star Clusters
There are no Messier objects within the Constellation of Corona Australis.
What is a Star Cluster?
FACT: A star cluster is a large group of Stars, of which there are 2 different types:
- Globular Clusters:
A global cluster is a spherical collection of ‘Old Stars,’ numbering hundreds to millions, that are tightly bound by gravity and orbits a galactic core.
- Open Clusters:
An open Cluster is a looser formation of ‘Young Stars’ that generally has less than a few hundred Stars.
What is the Milky Way?
The Milky Way is a Spiral Galaxy, containing over 200 billion Stars, and actually forms part of the Constellation of Sagittarius. It is the Galaxy that contains our solar system and it gets its name from the fact that it looks like a hazy swirl or river of milk across the sky.
It is made up of Gas, Dust and Stars, with spiral arms wrapped around it, and a massive black hole in the center of the Galaxy. Not all of the Stars in the Universe are contained within the Milky Way.
It is at its brightest if looking towards the galactic center in the direction of Sagittarius. The Stars that make up the Milky Way are many light years away and cannot all be individually identified by the naked eye.
The Constellation of Corona Australis lies alongside the Milky Way. It contains one of the closest star formations to our solar system.
The area of this star formation area is called the Corona Australis Molecular Cloud and houses stars in the early part of their lifespans. The two variable Stars – r Coronae Australis and t y Corona Australis -provide part of the light emissions from this nebula. The light emission brightness is therefore variable. The Corona Australis Molecular Cloud is a dusty dark nebula that is located around 430 light years from Earth,
Historical significance: the legends, and myths surrounding Constellation Corona Australis
In many cultures the various Constellations in the sky generate both intrigue and mystery.
For thousands of years, various cultures around the world have identified and named the constellation we know and see in the night sky as the crown.
The Babylonians also recorded details of various bright stars within the constellations in their Babylonian star catalogues before 100BCE.
There are many Greek myths and legends surrounding the origin and names of the constellations from Zeus to mythical creatures and objects.
The Corona Australis, the Southern Crown, was considered by the ancient Greeks to be a wreath, not a traditional crown.
One Greek myth involves Dionysus.
Dionysus saved his mother Semele, from Hades the god of the underworld and as a reward had a crown placed in the sky for him, represented as the Southern Crown (Corona Australis in Latin).
The Southern Crown is located between Constellation Sagittarius and Constellation Scorpius.
This myth is also associated with the Northern Crown in the sky (the Corona Borealis).
It was Ptolemy, the Greek/Roman astronomer who first listed the Constellation of Corona Australis, in the 2nd century AD.
Previous to that the Constellation of Corona Australis was not considered to be a separate constellation. It was in fact considered to be a circlet of Stars situated at the feet of the Centaur representing the neighboring Constellation of Sagittarius.
The words Corona Australis is used in many cultures, with different names, and meanings:
- In Latin – the Romans called Corona Australis the ‘Golden Crown of Sagittarius’ ‘Parvum Coelum’, the Canopy or little sky.
- In French – Sertum Australe, the ‘Southern Garland’
- Greek Meaning – the Poet Aratus wrote of two crowns in relation to the skies.
- In Mesopotamian times – it was referred to as MUL.APIN or MA.GUR, meaning ‘the Bark’
- German language – Corolla, ‘Little Crown’.
- In Chinese – it is associated with the Black Tortoise of the North, and the Heavenly Turtle.
What is the difference between a constellation and an asterism?
An asterism is a group of stars that appear to form a pattern in the night sky but with no officially determined boundaries. It can make up part of a constellation or cross the boundaries of an official constellation or even a defunct constellation. An asterism is a more vague assembly of stars than a recognized constellation.
The meteor showers
The Corona Australis Constellation is associated with 1 meteor shower known as ‘The Austrinids’. The Austrinids meteor shower occurs in the month of March each year.
Quick Facts about Corona Australis and Constellations – Did you know that?
- The Constellation of Corona Australis is not one of the 12 constellations of the Zodiac.
- The Constellation Corona Australis is one of the original 48 constellations identified by the Greek Astronomer Ptolemy. Ptolemy originally listed 13 Stars in the Constellation of Corona Australis but later moved one into the neighboring Constellation Telescopium.
- Constellation Corona Australis ranks as the 80th largest Constellation in the night sky
- The small Constellation Corona Australis only occupies 0.31% of the night sky
- The proper astronomical name is Constellation Corona Australis, but is sometimes abbreviated to ‘CrA’.
- Corona Australis includes a Star (HD 166724) that hosts one of the 5 most eccentric planets
- Meridiana is a main sequence Star located near the top left hand side of the crown shape.
- It is 31 times brighter, around 50% hotter and around 5 times bigger than the Sun.
- The Constellations are not part of the solar system; they are groups of stars that appear to form shapes that are visible from Earth.
- The largest Constellation is called Hydra and the smallest Constellation is called Crux.
- The Sun does not belong to any constellation.
- A Constellation does not actually exist as a fixed object, it is a group of bright stars that happen to be in a random place and are light years apart and ever moving. We see the pattern of their presence.
- The center of a Galaxy does not contain a Giant Star it contains a massive Black Hole.
- Two Stars within the Constellation of Corona Australis are designated Eta, yet the Greek letter Iota is not used as a name for a Star in this constellation.
- A Red Dwarf is not a Dwarf Planet it is a Star. Most common Stars are Red Dwarf (cool Stars)
- Spiral Galaxies make up about two thirds of all the Galaxies in the Universe
Commonly Asked Questions
Q. What is the celestial sphere?
A. In astronomy and navigation terms, the celestial sphere is imaginary.
This virtual sphere has a large radius that is concentric with Earth.
We can imagine all objects in the night sky as being projected upon the inside of this celestial sphere, as if it was images placed inside a dome.
Q. What prevents us seeing the Stars and Constellations in the night sky?
A. Light pollution, fog, city lights and artificial lights all limit our visibility of the objects in the sky at night.
The best views come from outside of cities where light pollution is less. Camping in the countryside is one of the best ways to get a better view of what’s up there in Space.
Q. Will the Constellations change over time?
A. The Constellations are continually on the move.
The images we form in our imagination to make objects, shapes and patterns out of the constellations have already shifted over time.
As we view the night skies from Earth they are likely to continue to do so and possibly in time the images may look very different.