The Latin name “Corona Borealis” translates to “the northern crown”, which was inspired by the constellation’s brightest stars that form a semicircular arc. The Corona Borealis constellation is closely associated with the legend of Theseus and the Minotaur in Greek mythology and is thought to actually represent a crown.
Corona Borealis belongs to the Ursa Major family of constellations. The brightest star in Corona Borealis is the white main-sequence star Alphecca, and around 5 stars in Corona Borealis constellation have been discovered to host planets.
The other primary stars of Corona Borealis are Nusakan, Theta, Delta, Gamma, Epsilon and Iota Coronae Borealis. While there are many important stars in Corona Borealis and many interesting deep-sky objects, there are no Messier objects in Corona Borealis, and no meteor showers are associated with this constellation.
History and Mythology Of The Corona Borealis Constellation
Corona Borealis was one of the first 48 constellations listed by the Greco-Roman astronomer Ptolemy. It was was listed in the 2nd century Almagest, written by Ptolemy.
In Greek mythology, it is thought to represent a crown given by Dionysus to Ariadne, the daughter of Minos of Crete after she had been abandoned by the Athenian prince Theseus. When Ariadne wore this crown at her marriage to Dionysus, he placed it in the heavens to commemorate their wedding.
However, in another version of the tale, Dionysus gave the crown to Ariadne, who in turn gave it to Theseus after he arrived in Crete to kill the minotaur. He then used the crown’s light to escape the labyrinth after killing the minotaur. Dionysus later set the crown in the heavens to commemorate this achievement.
Location Of The Corona Borealis Constellation
As mentioned above, Corona Borealis is the 73rd largest constellation in the sky and is considered to be fairly small. It is located in the third quadrant of the northern hemisphere (NQ3) and stretches for around 179 square degrees.
It can be seen at latitudes between +90° and -50°. It’s best seen at 9pm, during July and its right ascension is 15h 16m 03s – 16h 25m 07s and its declination is 39.7117195° – 25.5380573°.
Corona Borealis belongs to the Ursa Major family of constellations, along with along with Coma Berenices, Bootes, Camelopardalis, Canes Venatici, Draco, Leo Minor, Lynx, Ursa Major and Ursa Minor. It is surrounded by the constellations of Bootes, Hercules and Serpens Caput.
The main primary stars of Corona Borealis are Alphecca, Nusakan, Theta, Delta, Gamma, Epsilon and Iota Coronae Borealis. The brightest star is the white main-sequence star Alphecca.
Around 5 stars in Corona Borealis constellation have been discovered to host planets.
Alphecca, also known as Alpha Coronae Borealis, is the brightest star in Corona Borealis and the 67th brightest star in the night sky. It is composed of two main sequence stars and is around 75 light years away from us. Alphecca is a fast-spinning star, having a rotational velocity of around 139 km/86.3 miles per second.
The two primary stars are Alphecca A and Alphecca B. Alphecca A is a white main-sequence star while Alphecca B is a yellowish main-sequence star. Together, they have a magnitude of 2.23, but the stars eclipse each other and this results in brightness variations that range from magnitude 2.21 to 2.32.
Alphecca A is enveloped by a circumstellar disk of gas and dust. It has had many names, such as Alphecca Gemma, Gnosia, and Asteroth, but Alphecca has remained the favorite.
Alphecca A has 258% of our Sun’s mass and its radius is between 289% to 304% of the Sun’s radius. It is 74 times brighter than our Sun. Alphecca B is smaller than our Sun, having only 92% of our Sun’s mass and 90% of its radius.
Alphecca is one of the 15 Behenian Fixed Stars. These stars were considered in medieval times to have magical attributes and were associated with stars and other objects. Alphecca is also associated with Venus and Mercury.
Nusakan, also known as Beta Coronae Borealis, is the second brightest star in Coronae Borealis and is located around 112 light years away from us. A binary star, it has an apparent magnitude of that varies from 3.65 to 3.72.
The two primary stars are Beta Coronae Borealis A and Beta Coronae Borealis B. Beta Coronae Borealis A is a rapidly oscillating Ap star and has 209% of our Sun’s mass. It also has 263% of its radius and it is 25.3 times brighter.
Beta Coronae Borealis B is a main-sequence star with around 140% of our Sun’s mass. It has 156% of its radius and is 4.5 times brighter.
Gamma Coronae Borealis
Gamma Coronae Borealis is located around 146 light years away from us. It is a binary star with an apparent magnitude of 3.83 that can vary. It has two main sequence stars, with the primary star having around 251% of our Sun’s mass.
The primary star is a fast spinner, with a rotational velocity of 182 km/113 mi per second. Its surface temperature is 7,649 K, making it hotter than our Sun and it is overall 59 times brighter than our Sun.
Theta Coronae Borealis
Theta Coronae Borealis is another binary star. It is located around 380 light years away from us. It has two main stars — Theta Coronae Borealis A and Theta Coronae Borealis B. Theta Coronae Borealis A is a blue-white star with a magnitude of 4.13 and Theta Coronae Borealis B is a white main-sequence star of magnitude 6.29. Therefore, Theta Coronae Borealis has a combined apparent magnitude of 4.13.
Theta Coronae Borealis A has 600% of our Sun’s mass and 400% of its radius. It has a temperature of 14,910 K, making it twice as hot and 538 times brighter than our Sun. It is also classified as a Be shell star because it spins so fast — 393 km/244.1 mi per second — and the fact it is enveloped by a gaseous disk.
Theta Coronae Borealis B has 250% of our Sun’s mass and is located at around 86 AU away from the primary star.
Delta Coronae Borealis
Delta Coronae Borealis is located around 165 light years away from Earth. It is a variable star and it’s magnitude varies regularly between magnitude 4.57 and 4.69. It is a yellow giant star that has around 240% of our Sun’s mass and 740% of its radius. Delta Coronae Borealis is also 34.3 times brighter than our Sun.
Epsilon Coronae Borealis
Epsilon Coronae Borealis is around 221 light years away from Earth. It is a multiple star system that has a combined apparent magnitude of 4.13. Epsilon Coronae Borealis lies one degree north of the variable star T Coronae Borealis, which we will go into more detail about further on.
Epsilon Coronae Borealis has a primary star that is an orange giant that has around 144% of our Sun’s mass and 2,100% of its radius. It is 151 times brighter than our Sun and has an exoplanet around 6.7 times as massive as Jupiter.
Iota Coronae Borealis
Iota Coronae Borealis is around 312 light years away from us. It is a binary star with an apparent magnitude of 4.96. The two stars in it’s system are a chemically peculiar mercury-manganese star and an A-type star.
The chemically peculiar star is the primary star and it has a temperature of 10,727 K, making it twice as hot as the Sun and 90 times brighter.
T Coronae Borealis
T Coronae Borealis is also known as the Blaze star and it is an unusual type of star known as a recurrent nova. It usually has a magnitude of 10.8, but during an outburst, it reaches a magnitude of 2.0.
T Coronae Borealis is located at around 806 parsecs away from us. It is a binary star with a red giant star and a white dwarf.
The red giant star has 112% of our Sun’s mass and 7,500% of its radius. It is 655 times brighter than our Sun. The white dwarf star has 137% of our Sun’s mass and it is around 100 times brighter.
Rho Coronae Borealis
Rho Coronae Borealis is a yellow dwarf star and is actually very similar to our Sun. It is located at around 56.2 light years away from Earth and has an apparent magnitude of 5.4.
This star has 91% of our Sun’s mass and 136% of its radius. It is 1.7 times brighter than our Sun, too. It is also older than our Sun — around 10.2 billion years old!
R Coronae Borealis
R Coronae Borealis is a yellow supergiant star that is located at around 1,400 parsecs and has an apparent magnitude that varies from 5.71 to 14.8. It is the prototype of the R Cor Bor class of variable stars, which fade by several magnitudes at irregular intervals.
R Coronae Borealis is made up of around 90% helium and less than 1% hydrogen. The remainder is mostly carbon. It has only 80% of our Sun’s mass and around 8,500% of its radius. It is also around 10,000 times brighter than our Sun.
Kappa Coronae Borealis
Kappa Coronae Borealis is a K-type orange subgiant star with an apparent magnitude of +4.79. It is situated around 98.1 light years away from Earth. Kappa Coronae Borealis has around 132% of our Sun’s mass and 477% of its radius. It is cooler than our Sun, with a temperature of around 4,870 K, but it is 11.6 times brighter than our Sun.
It is the first first subgiant discovered to host a disk of dust around it. The disk extends to around 120 AU. What’s more, a giant planet orbits Kappa Coronae Borealis, but is unknown which planet or it’s nature.
Deep Sky Objects
As well as the notable stars mentioned above, the Corona Borealis constellation also hosts some deep sky objects. There are no Messier objects in Corona Borealis and no meteor showers are associated with this constellation.
NGC 6085 is a member of the Abell 2162 galaxy cluster. It is a spiral galaxy that is located at around 454 million light years away from us. It has an apparent magnitude of 14.5 and stretches for around 226,700 light years, making it much bigger than our milky way.
NGC 6086 is a the brightest galaxy in the Abell 2162 galaxy cluster. With a magnitude of 12.7, it is an elliptical galaxy and a supermassive black hole has been discovered in it.
Abell 2142 is a huge x-ray luminous galaxy cluster. It is luminous because of a still ongoing merge between two galaxy clusters. It stretches for around six million light years and contains hundreds of galaxies and enough galaxies to make thousands more.
Abell 2065 is another galaxy cluster, however it is highly concentrated and contains over 400 galaxies. It is located at around one billion light years away from our Solar System.
Corona Borealis Supercluster
The Corona Borealis Supercluster is, as its name suggests, a supercluster. This galaxy contains the galaxy clusters Abell 2056, 2061, 2065, 2067, 2079, 2089 and 2092. It is the most prominent of its kind in the northern celestial hemisphere.
It is around 330 million light years wide and 130 million light years deep. This supercluster is located around 964 million light years away from Earth!
- The Arabs called Corona Borealis “Alphecca”. This is now the name of its brightest star and means “separated”.
- Corona Borealis was called Caer Aarinhod, “the Castle of the Silver Circle”, in Welsh Mythology.
- The Skidi people of Native Americans saw the stars of Corona Borealis as representing a council of stars whose chief was Polaris.
- The ancient Balts called Corona Borealis Darzelis, meaning “the flower garden”.
- Polynesian peoples often recognized Corona Borealis. The people of the Tuamotus named it “Na Kaua-ki-tokerau” and probably “Te Hetu”.
- In Australian Aboriginal astronomy, the constellation is called Womera — “the boomerang” — due to the shape of the stars.
- Corona Borealis 1 – http://www.astronomytrek.com/star-constellation-facts-corona-borealis/
- Alphecca – https://nineplanets.org/corona-borealis-constellation/
- T Coronae Borealis – https://skyandtelescope.org/observing/celestial-objects-to-watch/r-and-t-coronae-borealis-two-stellar-opposites/
- R Coronae Borealis – https://skyandtelescope.org/observing/variable-star-r-coronae-borealis-pluto-occults-star/
- Kappa Coronae Borealis – https://theskylive.com/sky/stars/kappa-coronae-borealis-star
- NGC 6085 – https://en.wikipedia.org/wiki/NGC_6085
- Abell 2142 – https://en.wikipedia.org/wiki/Abell_2142
- Abell 2065 – https://en.wikipedia.org/wiki/Abell_2065
- Corona Borealis Supercluster – http://www.atlasoftheuniverse.com/superc/cbo.html
- Some Images created with the NightVision app – https://www.nvastro.com/nvj.html
- Some Images created with the Stelvision Sky Map https://www.stelvision.com/en/sky-map/