List of stars in Corona Borealis
|Pronunciation||/ /, genitive //|
|Symbolism||The Northern Crown|
|Right ascension||16 h|
|Area||179 sq. deg. (73rd)|
|Stars with planets||4|
|Stars brighter than 3.00m||4|
|Stars within 10.00 pc (32.62 ly)||0|
|Brightest star||α CrB (Alphecca or Gemma) (2.21m)|
|Nearest star||HD 144579
(46.86 ly, 17.25 pc)
Corona Borealis (pron.: / /) is a small constellation in the northern sky. Its name is Latin for "northern crown", a name inspired by its shape; its main stars form a semicircular arc. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy and remains one of the 88 modern constellations.
Notable features 
The seven stars that make up the constellation's figure are all 4th-magnitude stars, except for the constellation's brightest star, Alpha Coronae Borealis. This blue-white main-sequence star, also called Alphekka and Gemma, is of magnitude 2.2, though it is an Algol-type eclipsing variable star. It varies by 0.1 magnitudes with a period of 17.4 days. Alphekka is 75 light-years from Earth.
Corona Borealis is home to several binary and double stars. Zeta Coronae Borealis is a double star divisible in small telescopes. It has two blue-white components, 470 light-years from Earth. The primary is of magnitude 5.0 and the secondary is of magnitude 6.0. Another double star is Nu Coronae Borealis; both components are 550 light-years from Earth but have different radial velocities and are assumed to be unrelated. The primary, Nu1 Coronae Borealis, is a red-hued giant star of magnitude 5.2; the secondary, Nu2 Coronae Borealis is an orange-hued giant star of magnitude 5.4. Sigma Coronae Borealis, on the other hand, is a true binary star. Both components are yellow and orbit each other every 1000 years. The system, 71 light-years from Earth, has a primary of magnitude 5.6 and a secondary of magnitude 6.6. Sigma Coronae Borealis is divisible by small amateur telescopes.
Corona Borealis is home to two remarkable variable stars. T Coronae Borealis is an exploding variable star also known as the Blaze Star. Normally placid around magnitude 10—it has a minimum of 10.2 and maximum of 9.9—it brightens to magnitude 2 in a period of hours, caused by a nuclear chain reaction and the subsequent explosion. T Coronae Borealis is one of a handful of stars called recurrent novae, which include RS Ophiuchi, T Pyxidis, V1017 Sagitarii, and U Scorpii. An outburst of T Coronae Borealis was first recorded in 1866; its most recent outburst was in February 1946. T Coronae Borealis is a binary star with a red-hued giant primary and a small blue secondary; its period is approximately 8 months. R Coronae Borealis is a yellow-hued variable supergiant star, over 7000 light-years from Earth. Normally of magnitude 6, its brightness periodically drops as low as magnitude 15 and then slowly increases over the next several months. Though small dips in brightness occur sporadically, extreme decreases happened most recently in 1962, 1972, and 1977. Small carbon particles building up in the stellar atmosphere may be responsible.
Named stars 
|Bayer||Name||Origin||Meaning The Northern Crown|
|α||Alphekka/Gemma||Arabic||"The broken" crown of stars|
|β||Nusakan||Arabic||The two series|
|T||Blaze Star||English||The star that blazes|
Deep sky objects 
Corona Borealis contains no bright deep sky objects. Abell 2065 is a highly concentrated galaxy cluster containing over 400 members, the brightest of which are 16th magnitude. The cluster is more than one billion light-years from Earth.
History and mythology 
In Greek mythology, Corona Borealis was sometimes considered to represent a crown that was given by Dionysus to Ariadne, the daughter of Minos of Crete. When she wore the crown to her wedding, where she married Dionysus, he placed her crown in the heavens to commemorate the wedding. In Welsh mythology, it was called Caer Arianrhod, "the Castle of the Silver Circle", and was the heavenly abode of the Lady Arianrhod (Squire, 2000:154–155). In Arabic mythology, the constellation was known as "the bowl of the poor people" from the Arabic name قصعة المساكين, since the stars form an unsymmetrical pattern with an indent in one side, similar to the bowl of the poor. The Arabs also called the constellation Alphecca (a name later given to Alpha Corona Borealis), which means separated or broken up since the stars of Corona Borealis resembles a loose string of jewels.
The Cheyenne nation of Native Americans called the main stars of this constellation the "Camp Circle" as they arranged their camps in a semicircle. Native Americans also used stars to make designs in the ground at the Medicine Wheel in Bighorn National Forest, Wyoming, USA
Polynesian peoples often recognized Corona Borealis, though only one name is known for its leading star, Gemma; it was likely called Te Hetu in the Tuamotus, whose people called the constellation Na Kaua-ki-tokerau. In Hawaii, the constellation was likely called Kaua-mea; it was called Rangawhenua in New Zealand. The figure of Corona Borealis was called Te Wale-o-Awitu in Pukapuka. Its name in Tonga was unsure; it was either called Ao-o-Uvea or Kau-kupenga.
See also 
- Ridpath & Tirion 2001, pp. 126–128.
- Levy 2005, pp. 70–71.
- Paul Kunitzch and Tom Smart, A Short Guide to Modern Star Names and their Derivations (Harrassowitz, 1986).
- p. 151, Star Lore: Myths, Legends, and Facts, William Tyler Olcott, New York, Dover Publication Inc., 2004
- (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 26 日
- Makemson 1941, p. 282.
- Levy, David H. (2005). Deep Sky Objects. Prometheus Books. ISBN 978-1-59102-361-6.
- Makemson, Maud Worcester (1941). The Morning Star Rises: an account of Polynesian astronomy. Yale University Press.
- Ridpath, Ian; Tirion, Wil (2001). Stars and Planets Guide. Princeton University Press. ISBN 978-0-691-08913-3.
- Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0-00-725120-9. Princeton University Press, Princeton. ISBN 978-0-691-13556-4.
- Squire, C. (2000). The mythology of the British Islands: an introduction to Celtic myth, legend, poetry and romance. London & Ware: UCL & Wordsworth Editions Ltd.
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