Corona Borealis

Corona Borealis

Constellation
List of stars in Corona Borealis
Abbreviation	CrB
Genitive	Coronae Borealis
Pronunciation	/kəˈroʊnə ˌbɔːriˈælɪs, -ˌboʊ-, -ˈeɪlɪs/, genitive /kəˈroʊni/[1][2]
Symbolism	The Northern Crown
Right ascension	15h 16m 03.8205s–16h 25m 07.1526s[3]
Declination	39.7117195°–25.5380573°[3]
Area	179 sq. deg. (73rd)
Main stars	7
Bayer/Flamsteed stars	24
Stars with planets	5
Stars brighter than 3.00m	1
Stars within 10.00 pc (32.62 ly)	0
Brightest star	α CrB (Alphecca or Gemma) (2.21m)
Messier objects	0
Meteor showers	None
Bordering constellations	Hercules Boötes Serpens Caput
Visible at latitudes between +90° and −50°. Best visible at 21:00 (9 p.m.) during the month of July.

Corona Borealis is a small constellation in the Northern Celestial Hemisphere. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Its brightest stars form a semicircular arc. Its Latin name, inspired by its shape, means "northern crown". In classical mythology Corona Borealis generally represented the crown given by the god Dionysus to the Cretan princess Ariadne and set by her in the heavens. Other cultures likened the pattern to a circle of elders, an eagle's nest, a bear's den or a smokehole. Ptolemy also listed a southern counterpart, Corona Australis, with a similar pattern.

The brightest star is the magnitude 2.2 Alpha Coronae Borealis. The yellow supergiant R Coronae Borealis is the prototype of a rare class of giant stars—the R Coronae Borealis variables—that are extremely hydrogen deficient, and thought to result from the merger of two white dwarfs. T Coronae Borealis, also known as the Blaze Star, is another unusual type of variable star known as a recurrent nova. Normally of magnitude 10, it last flared up to magnitude 2 in 1946, and is predicted to do the same in 2024. ADS 9731 and Sigma Coronae Borealis are multiple star systems with six and five components respectively. Five star systems have been found to have Jupiter-sized exoplanets. Abell 2065 is a highly concentrated galaxy cluster one billion light-years from the Solar System containing more than 400 members, and is itself part of the larger Corona Borealis Supercluster.