Northern Crown (Corona Borealis)

The Northern Crown, known in Latin as Corona Borealis, is a small but distinctive constellation located in the northern celestial hemisphere. Recognised since antiquity, it is notable for its semi-circular arrangement of stars resembling a jewelled crown. The constellation lies between Boötes to the west and Hercules to the east, forming a prominent arc that is easily identifiable in clear northern skies. Despite its modest size, Corona Borealis holds significant mythological, historical, and astronomical importance.

Astronomical Characteristics

Corona Borealis is a relatively small constellation covering an area of approximately 179 square degrees, ranking 73rd in size among the 88 modern constellations. It lies within the northern celestial hemisphere, with coordinates roughly between right ascension 15h 16m to 16h 25m and declination +26° to +40°. The constellation is best observed during late spring and summer in the Northern Hemisphere, particularly around June and July, when it reaches its highest point in the night sky.
The brightest star in Corona Borealis is Alphecca (also known as Gemma or Alpha Coronae Borealis), a binary star system located approximately 75 light years from Earth. Alphecca has an apparent magnitude of 2.21, making it easily visible to the naked eye. Its secondary component is a faint companion star, and together they form a spectroscopic binary. Other notable stars in the constellation include Nusakan (Beta Coronae Borealis), a chemically peculiar variable star, and Gamma Coronae Borealis, another binary system.

Mythological Background

In ancient Greek mythology, Corona Borealis is associated with the legend of Ariadne, the daughter of King Minos of Crete. After aiding Theseus in slaying the Minotaur and escaping the Labyrinth, Ariadne was abandoned by him on the island of Naxos. The god Dionysus (Bacchus) found her there, fell in love, and married her. According to myth, Dionysus placed her bridal crown among the stars as a symbol of his eternal affection, thus forming the Northern Crown.
The constellation has appeared in several ancient cultures under different interpretations. The Romans adopted the Greek association with Ariadne’s crown, while the Arab astronomers referred to it as “Alphecca,” meaning the bright one of the broken ring. The Chinese recognised its brightest stars as part of an asterism known as “The Twisted Jade Ornament.”

Observation and Visibility

Corona Borealis is best viewed from latitudes between +90° and -50°, being circumpolar for northern observers at high latitudes. Its signature semicircular pattern makes it easy to identify even in regions with moderate light pollution. The constellation culminates at midnight around mid-June, making it a highlight of summer night skies in Europe and North America.
For amateur astronomers, Alphecca serves as a useful reference point when locating nearby constellations such as Hercules, Boötes, and Serpens Caput. Binoculars or small telescopes can reveal several interesting variable and double stars, as well as deep-sky objects.

Deep-Sky Objects and Astronomical Phenomena

Though not rich in bright nebulae or galaxies, Corona Borealis hosts several interesting deep-sky objects. Among them, the Corona Borealis Galaxy Cluster (Abell 2065) stands out. It is located roughly 1 billion light years away and contains thousands of galaxies. The cluster is part of a larger supercluster structure within the Corona Borealis Supercluster, a region known for its high density of galaxies.
Additionally, the constellation is home to several variable stars of interest to astronomers:

• R Coronae Borealis, the prototype of a rare class of variable stars known as R Coronae Borealis variables, is famous for its unpredictable dimming events caused by dust formation around the star.
• T Coronae Borealis, nicknamed the “Blaze Star,” is a recurrent nova that has undergone dramatic outbursts, notably observed in 1866 and 1946, when it brightened significantly before fading again.

Historical and Cultural Significance

The Northern Crown has held symbolic meaning across civilisations for millennia. In ancient Greek and Roman societies, it symbolised victory, royalty, and divine love. In mediaeval star charts, the constellation was frequently depicted as a crown adorned with jewels, often worn by mythological figures or celestial personifications.
In Arabic astronomy, Corona Borealis’ stars were associated with agricultural and seasonal cycles. In the Native American traditions of the Plains and Great Lakes tribes, it was sometimes seen as a campfire circle or council ring, reflecting communal unity and cooperation.
The constellation was officially listed among the 88 modern constellations recognised by the International Astronomical Union (IAU) in 1922, cementing its place in modern celestial cartography.

Scientific Studies and Discoveries

Modern astrophysical studies of Corona Borealis have contributed significantly to the understanding of stellar evolution and galactic clustering. The R Coronae Borealis stars, for instance, have been studied to understand the late evolutionary stages of hydrogen-deficient supergiants and the mechanisms of dust ejection. Observations of the Corona Borealis Supercluster have provided valuable insights into large-scale cosmic structures and the distribution of dark matter.
The recurrent nova T Coronae Borealis continues to attract scientific interest due to its unpredictable eruptions, which provide an opportunity to study mass transfer in binary systems involving white dwarfs and red giants.