Constellation of Corona Borealis star map

Abbreviation: CrB

Genitive: Coronae Borealis

English: The Northern Crown

Size Ranking: 73rd

Area: 179 square degrees

Fully Visible: 90°N-50°S

Corona Borealis-The Northern Crown is an ancient constellation, and represents the crown worn by Ariadne, the mythical Princess of Crete, when she married the god, Dionysius, more popularly known as Bacchus, the god of wine, who threw it into the sky, where its jewels turned into stars. This constellation consists of an arc of seven stars, all of which, except for one, are of fourth magnitude or higher. The brightest star in this constellation, αCrB, is called either Alphekka, derived from the Arabic name for the constellation, or, appropriately, Gemma, Latin for ‘jewel’. Corona Borealis contains a famous cluster of galaxies more than 1000 million light years away, being so distant that they are no brighter than 16th magnitude and thus far beyond the reach of amateur telescopes.

By imagining a line joining Arcturus, αBoo, and Vega, αLyr,  σCrB is close to the midpoint of this line and the Crown is up to the left.

Features of Interest:

αCrB, named Alphekka and/or Gemma, is a blue-white main-sequence star, magnitude 2.2 and 75ly away. It is an eclipsing binary of the  Algol type, but its variation every 17.4 days is only 0.1 magnitude, hence too slight to be noticeable to the naked eye.

βCrB, named Nusakan, is a yellow-white star, 58ly away and magnitude 3.7.

γCrB, is a blue-white star, magnitude 3.8 and 208ly distant.

δCrB, is a yellow star, 124 ly from Earth and magnitude 4.6.

εCrB, is a pair of orange stars, magitudes 4.2 and 12.6, separation 1.8”, PA 003° (try the new telescope on this one!).

ζCrB, 470 ly distant, is a pair of blue-white stars, magnitudes 5.0 and6.0, separation 6.3”, PA 305°.

ν¹,ν²CrB, is a wide binocular pair of red and orange giants of magnitudes 5.2 and 5.4, both about 550ly away but moving in different directions, so probably not a true binary.

σCrB, is apair of yellow stars of magnitudes 5.6 and 6.6, separation 7.0”, PA 234°. They form a genuine binary with an estimated orbital period of 1000 years.

TCrB, is a spectacular variable star, known as the ‘Blaze Star’. It is a recurrent nova,usually slumbering at around magnitude 11, but can suddenly and unpredictably brighten to magnitude 2. Its last recorded outburst was in 1946 and the previous one was 80 years before that. It is not known when it may erupt again.



1. Redshift 2 – Maris Multimedia

2. The Guiness Book of Astronomy – Patrick Moore

3. Stars and Planets – Ian Ridpath and Wil Tirion

4. Where the Stars Are – Orion.

5. Sky Charts – Cartes du Ciel V 2.75