Corona Borealis

Coordinates: Sky map 16h 00m 00s, +30° 00′ 00″
Source: Wikipedia, the free encyclopedia.
"Northern Crown" redirects here. For the d20 System game, see Northern Crown (roleplaying game).

Corona Borealis
Constellation
73rd)
Main stars7
Bayer/Flamsteed
stars		24
Stars with planets5
Stars brighter than 3.00m1
Stars within 10.00 pc (32.62 ly)0
Brightest starα CrB (Alphecca or Gemma) (2.21m)
Messier objects0
Meteor showersNone
Bordering
constellations
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

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

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
.

Characteristics

Covering 179 square degrees and hence 0.433% of the sky, Corona Borealis ranks 73rd of the

Southern Celestial Hemisphere.[8]

Features

Stars

See also: List of stars in Corona Borealis

The seven stars that make up the constellation's distinctive crown-shaped pattern are all 4th-magnitude stars except for the brightest of them,

Zeta2. John Flamsteed did likewise with Nu Coronae Borealis; classed by Bayer as a single star, it was noted to be two close stars by Flamsteed. He named them 20 and 21 Coronae Borealis in his catalogue, alongside the designations Nu1 and Nu2 respectively.[9] Chinese astronomers deemed nine stars to make up the asterism, adding Pi and Rho Coronae Borealis.[10] Within the constellation's borders, there are 37 stars brighter than or equal to apparent magnitude 6.5.[b][5]

The constellation Corona Borealis as it can be seen by the naked eye

Alpha Coronae Borealis (officially named Alphecca by the IAU, but sometimes also known as Gemma) appears as a blue-white star of magnitude 2.2.

Ursa Major Moving Group of stars that have a common motion through space.[17]

Located 112±3 light-years away,

spectroscopic binary system whose two components are separated by 10 AU and orbit each other every 10.5 years.[18] The brighter component is a rapidly oscillating Ap star,[19] pulsating with a period of 16.2 minutes. Of spectral type A5V with a surface temperature of around 7980 K, it has around 2.1 M☉, 2.6 solar radii (R☉), and 25.3 L☉. The smaller star is of spectral type F2V with a surface temperature of around 6750 K, and has around 1.4 M☉, 1.56 R☉, and between 4 and 5 L☉.[20] Near Nusakan is Theta Coronae Borealis, a binary system that shines with a combined magnitude of 4.13 located 380±20 light-years distant.[16] The brighter component, Theta Coronae Borealis A, is a blue-white star that spins extremely rapidly—at a rate of around 393 km per second. A Be star, it is surrounded by a debris disk.[21]

Flanking Alpha to the east is Gamma Coronae Borealis, yet another binary star system, whose components orbit each other every 92.94 years and are roughly as far apart from each other as the Sun and Neptune.[22] The brighter component has been classed as a Delta Scuti variable star,[23] though this view is not universal.[22] The components are main sequence stars of spectral types B9V and A3V.[24] Located 170±2 light-years away,[16] 4.06-magnitude Delta Coronae Borealis is a yellow giant star of spectral type G3.5III that is around 2.4 M☉ and has swollen to 7.4 R☉. It has a surface temperature of 5180 K.[25] For most of its existence, Delta Coronae Borealis was a blue-white main-sequence star of spectral type B before it ran out of hydrogen fuel in its core. Its luminosity and spectrum suggest it has just crossed the Hertzsprung gap, having finished burning core hydrogen and just begun burning hydrogen in a shell that surrounds the core.[26]

arcseconds apart that can be readily separated at 100x magnification. The primary is of magnitude 5.1 and the secondary is of magnitude 6.0.[27] Nu Coronae Borealis is an optical double, whose components are a similar distance from Earth but have different radial velocities, hence are assumed to be unrelated.[28] The primary, Nu1 Coronae Borealis, is a red giant of spectral type M2III and magnitude 5.2, lying 640±30 light-years distant,[16][29] and the secondary, Nu2 Coronae Borealis, is an orange-hued giant star of spectral type K5III and magnitude 5.4, estimated to be 590±30 light-years away.[16][30] Sigma Coronae Borealis, on the other hand, is a true multiple star system divisible by small amateur telescopes.[13] It is actually a complex system composed of two stars around as massive as the Sun that orbit each other every 1.14 days, orbited by a third Sun-like star every 726 years. The fourth and fifth components are a binary red dwarf system that is 14,000 AU distant from the other three stars.[31] ADS 9731 is an even rarer multiple system in the constellation, composed of six stars, two of which are spectroscopic binaries.[32][c]

Corona Borealis is home to two remarkable

recurrent novae, which include T Pyxidis and U Scorpii. An outburst of T Coronae Borealis was first recorded in 1866; its second recorded outburst was in February 1946.[35][36] T Coronae Borealis started dimming in March 2023 and it is known that before it goes nova it dims for about a year; for this reason it is expected to go nova at any time between March and September, 2024.[37] T Coronae Borealis is a binary star with a red-hued giant primary and a white dwarf secondary, the two stars orbiting each other over a period of approximately 8 months.[38] R Coronae Borealis is a yellow-hued variable supergiant star, over 7000 light-years from Earth, and prototype of a class of stars known as R Coronae Borealis variables. Normally of magnitude 6, its brightness periodically drops as low as magnitude 15 and then slowly increases over the next several months.[39] These declines in magnitude come about as dust that has been ejected from the star obscures it. Direct imaging with the Hubble Space Telescope shows extensive dust clouds out to a radius of around 2000 AU from the star, corresponding with a stream of fine dust (composed of grains 5 nm in diameter) associated with the star's stellar wind and coarser dust (composed of grains with a diameter of around 0.14 µm) ejected periodically.[40]

There are several other variables of reasonable brightness for amateur astronomer to observe, including three Mira-type long period variables:[33] S Coronae Borealis ranges between magnitudes 5.8 and 14.1 over a period of 360 days.[41] Located around 1946 light-years distant, it shines with a luminosity 16,643 times that of the Sun and has a surface temperature of 3033 K.[42] One of the reddest stars in the sky,[33] V Coronae Borealis is a cool star with a surface temperature of 2877 K that shines with a luminosity 102,831 times that of the Sun and is a remote 8810 light-years distant from Earth.[42] Varying between magnitudes 6.9 and 12.6 over a period of 357 days,[43] it is located near the junction of the border of Corona Borealis with Hercules and Bootes.[33] Located 1.5° northeast of Tau Coronae Borealis, W Coronae Borealis ranges between magnitudes 7.8 and 14.3 over a period of 238 days.[44] Another red giant, RR Coronae Borealis is a M3-type semiregular variable star that varies between magnitudes 7.3 and 8.2 over 60.8 days.[45] RS Coronae Borealis is yet another semiregular variable red giant, which ranges between magnitudes 8.7 to 11.6 over 332 days.[46] It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).[47] Meanwhile, U Coronae Borealis is an Algol-type eclipsing binary star system whose magnitude varies between 7.66 and 8.79 over a period of 3.45 days[48]

TY Coronae Borealis is a pulsating white dwarf (of ZZ Ceti) type, which is around 70% as massive as the Sun, yet has only 1.1% of its diameter.[49] Discovered in 1990, UW Coronae Borealis is a low-mass X-ray binary system composed of a star less massive than the Sun and a neutron star surrounded by an accretion disk that draws material from the companion star. It varies in brightness in an unusually complex manner: the two stars orbit each other every 111 minutes, yet there is another cycle of 112.6 minutes, which corresponds to the orbit of the disk around the degenerate star. The beat period of 5.5 days indicates the time the accretion disk—which is asymmetrical—takes to precess around the star.[50]

Extrasolar planetary systems

XO Telescope. Roughly the size of Jupiter, it completes an orbit around its star every three days.[57]

The discovery of a Jupiter-sized planetary companion was announced in 1997 via analysis of the radial velocity of Rho Coronae Borealis, a yellow main sequence star and

habitable zone were calculated for the binary star Eta Coronae Borealis,[61] which is composed of two stars—yellow main sequence stars of spectral type G1V and G3V respectively—similar in mass and spectrum to the Sun.[62] No planet has been found, but a brown dwarf companion about 63 times as massive as Jupiter with a spectral type of L8 was discovered at a distance of 3640 AU from the pair in 2001.[63]

Deep-sky objects

X-ray image of galaxy cluster Abell 2142

Corona Borealis contains few galaxies observable with amateur telescopes.

billion light-years away.[d][66] Another galaxy cluster in the constellation, RX J1532.9+3021, is approximately 3.9 billion light-years from Earth.[67] At the cluster's center is a large elliptical galaxy containing one of the most massive and most powerful supermassive black holes yet discovered.[67] Abell 2065 is a highly concentrated galaxy cluster containing more than 400 members, the brightest of which are 16th magnitude; the cluster is more than one billion light-years from Earth.[34] On a larger scale still, Abell 2065, along with Abell 2061, Abell 2067, Abell 2079, Abell 2089, and Abell 2092, make up the Corona Borealis Supercluster.[68] Another galaxy cluster, Abell 2162, is a member of the Hercules Superclusters.[69]

Mythology

Hercules and Corona Borealis, as depicted in Urania's Mirror (c. 1825)

In Greek mythology, Corona Borealis was linked to the legend of Theseus and the minotaur. It was generally considered 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 she wore the crown at her marriage to Dionysus, he placed it in the heavens to commemorate their wedding.[34] An alternative version has the besotted Dionysus give the crown to Ariadne, who in turn gives it to Theseus after he arrives in Crete to kill the minotaur that the Cretans have demanded tribute from Athens to feed. The hero uses the crown's light to escape the labyrinth after disposing of the creature, and Dionysus later sets it in the heavens. The Latin author Hyginus linked it to a crown or wreath worn by Bacchus (Dionysus) to disguise his appearance when first approaching Mount Olympus and revealing himself to the gods, having been previously hidden as yet another child of Jupiter's trysts with a mortal, in this case Semele. Corona Borealis was one of the 48 constellations mentioned in the Almagest of classical astronomer Ptolemy.[9]

In

Mesopotamia, Corona Borealis was associated with the goddess Nanaya.[70]

In Welsh mythology, it was called Caer Arianrhod, "the Castle of the Silver Circle", and was the heavenly abode of the Lady Arianrhod.[71] To the ancient Balts, Corona Borealis was known as Darželis, the "flower garden."[72]

The Arabs called the constellation Alphecca (a name later given to Alpha Coronae Borealis), which means "separated" or "broken up" (الفكة al-Fakkah), a reference to the resemblance of the stars of Corona Borealis to a loose string of jewels.

Bedouins, the constellation was known as qaṣʿat al-masākīn (قصعة المساكين), or "the dish/bowl of the poor people".[75]

The Skidi people of Native Americans saw the stars of Corona Borealis representing a council of stars whose chief was Polaris.[76] The constellation also symbolised the smokehole over a fireplace, which conveyed their messages to the gods, as well as how chiefs should come together to consider matters of importance.[77] The Shawnee people saw the stars as the Heavenly Sisters, who descended from the sky every night to dance on earth. Alphecca signifies the youngest and most comely sister, who was seized by a hunter who transformed into a field mouse to get close to her. They married though she later returned to the sky, with her heartbroken husband and son following later.[74] The Mi'kmaq of eastern Canada saw Corona Borealis as Mskegwǒm, the den of the celestial bear (Alpha, Beta, Gamma and Delta Ursae Majoris).[78]

Polynesian peoples often recognized Corona Borealis; the people of the Tuamotus named it Na Kaua-ki-tokerau and probably Te Hetu. The constellation was likely called Kaua-mea in Hawaii, Rangawhenua in New Zealand, and Te Wale-o-Awitu in the Cook Islands atoll of Pukapuka. Its name in Tonga was uncertain; it was either called Ao-o-Uvea or Kau-kupenga.[79]

In Australian Aboriginal astronomy, the constellation is called womera ("the boomerang") due to the shape of the stars.[80] The Wailwun people of northwestern New South Wales saw Corona Borealis as mullion wollai "eagle's nest", with Altair and Vega—each called mullion—the pair of eagles accompanying it.[81] The Wardaman people of northern Australia held the constellation to be a gathering point for Men's Law, Women's Law and Law of both sexes come together and consider matters of existence.[82]

Later references

Corona Borealis was renamed Corona Firmiana in honour of the Archbishop of Salzburg in the 1730 Atlas Mercurii Philosophicii Firmamentum Firminianum Descriptionem by Corbinianus Thomas, but this was not taken up by subsequent cartographers.

Corona Borealis in 2002.[85]

See also

  • Corona Borealis (Chinese astronomy)

Notes

  1. ^ While parts of the constellation technically rise above the horizon to observers between the 50°S and 64°S, stars within a few degrees of the horizon are to all intents and purposes unobservable.[5]
  2. ^ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[11]
  3. ^ The components are organised thus: Aa and Ab are yellow-white main sequence stars of spectral types F4V and F5V and 1.35 and 1.32 solar masses respectively, which orbit each other every 3.27 days. This pair is in a 450-year orbit with star B, a star of spectral type G4V that has around the same mass as the Sun. Star C is a yellow white star of spectral type F3V around 1.41 times as massive as the Sun, which has just started brightening and moving off the main sequence. It is in a 1000-year orbit with a pair of stars, Da and Db, a yellow-white main sequence star of spectral type F7V and a red dwarf of spectral type M3V. Da and Db take 14.28 days to orbit each other. Finally the system of stars C and Dab, and the system of stars Aab and B, take more than 20,000 years to orbit each other.[32]
  4. ^ Distance calculated from redshift.

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Cited texts

  • Ridpath, Ian; Tirion, Wil (2001). Stars and Planets Guide. Princeton, New Jersey: Princeton University Press.
    ISBN 978-0-691-08913-3
    .

External links


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