Corona Borealis#Deep sky objects

Covering 179 square degrees and hence 0.433% of the sky, Corona Borealis ranks 73rd of the IAU designated constellations by area. Its position in the Northern Celestial Hemisphere means that the whole constellation is visible to observers north of 50°S.{{cite web| url=http://www.ianridpath.com/constellations1.html | title=Constellations: Andromeda–Indus | work= Star Tales |author=Ridpath, Ian|publisher=self-published | access-date= 9 September 2014| author-link=Ian Ridpath }}{{efn|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.}} It is bordered by Boötes to the north and west, Serpens Caput to the south, and Hercules to the east. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "CrB".{{cite journal | last=Russell | first=Henry Norris |author-link=Henry Norris Russell | title=The New International Symbols for the Constellations | journal=Popular Astronomy | volume=30 | page=469 | bibcode=1922PA.....30..469R | year=1922 }} The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of eight segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between {{RA|15|16.0}} and {{RA|16|25.1}}, while the declination coordinates are between 39.71° and 25.54°.{{Cite journal | title=Corona Borealis, Constellation Boundary | journal=The Constellations | publisher=International Astronomical Union | url=https://www.iau.org/public/themes/constellations/#crb | access-date=12 October 2013 }} It has a counterpart—Corona Australis—in the Southern Celestial Hemisphere.{{cite book|last=Cornelius|first=Geoffrey|title=Complete Guide to the Constellations: The Starwatcher's Essential Guide to the 88 Constellations, Their Myths and Symbols|publisher=Duncan Baird Publishers|location=London, United Kingdom|date=2005|pages=70–71|isbn=978-1-84483-103-6}}

{{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, Alpha Coronae Borealis. The other six stars are Theta, Beta, Gamma, Delta, Epsilon and Iota Coronae Borealis. The German cartographer Johann Bayer gave twenty stars in Corona Borealis Bayer designations from Alpha to Upsilon in his 1603 star atlas Uranometria. Zeta Coronae Borealis was noted to be a double star by later astronomers and its components designated Zeta¹ and 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.{{cite book | last = Wagman | first = Morton | year = 2003 | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others | publisher = The McDonald & Woodward Publishing Company | location = Blacksburg, Virginia | isbn = 978-0-939923-78-6 |pages=117–18}} Chinese astronomers deemed nine stars to make up the asterism, adding Pi and Rho Coronae Borealis.{{cite web| url=http://www.ianridpath.com/startales/coronaborealis.html#chinese | title=Corona Borealis |last1=Ridpath|first1=Ian|publisher=self-published |work=Star Tales | access-date= 24 November 2014}} Within the constellation's borders, there are 37 stars brighter than or equal to apparent magnitude 6.5.{{efn|1=Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.{{cite web|url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|title=The Bortle Dark-Sky Scale|last=Bortle|first=John E.|date=February 2001|work=Sky & Telescope|access-date=29 November 2014|archive-date=31 March 2014|archive-url=https://web.archive.org/web/20140331202746/http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|url-status=dead}}}}

File:CoronaBorealisCC.jpg

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.{{cite journal

| author=Johnson, H. L.

| author2=Iriarte, B.

| author3=Mitchell, R. I.

| author4=Wisniewskj, W. Z.

| title=UBVRIJKL photometry of the bright stars

| journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99

| date=1966

| bibcode=1966CoLPL...4...99J }} In fact, it is an Algol-type eclipsing binary that varies by 0.1 magnitude with a period of 17.4 days.{{sfn|Ridpath|Tirion|2001|pp=126–28}} The primary is a white main-sequence star of spectral type A0V that is 2.91 times the mass of the Sun ({{Solar mass|link=y}}) and 57 times as luminous ({{Solar luminosity|link=y}}), and is surrounded by a debris disk out to a radius of around 60 astronomical units (AU).{{cite journal|author1=Pawellek, Nicole |author2=Krivov, Alexander V. |author3=Marshall, Jonathan P. |author4=Montesinos, Benjamin |author5=Ábrahám, Péter |author6=Moór, Attila |author7=Bryden, Geoffrey |author8=Eiroa, Carlos |date=2014|title=Disk Radii and Grain Sizes in Herschel-resolved Debris Disks|journal=The Astrophysical Journal|volume=792|issue=1|id=65|pages=19|bibcode=2014ApJ...792...65P | doi=10.1088/0004-637X/792/1/65|arxiv = 1407.4579 |s2cid=119282523 }} The secondary companion is a yellow main-sequence star of spectral type G5V that is a little smaller (0.9 times) the diameter of the Sun.{{cite journal |author1=Güdel, M. |author2=Arzner, K. |author3=Audard, M. |author4=Mewe, R. | title=Tomography of a Stellar X-ray Corona: Alpha Coronae Borealis | journal=Astronomy and Astrophysics | volume=403 | pages=155–71 |date=2003 | doi=10.1051/0004-6361:20030257 | bibcode=2003A&A...403..155G| doi-access=free | url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A53864/datastream/PDF/G%C3%BCdel-2003-Tomography_of_a_stellar_X-ray_corona-%28published_version%29.pdf }} Lying 75±0.5 light-years from Earth,{{cite journal | first=F. | last=van Leeuwen | title=Validation of the New Hipparcos Reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–64 | date=2007 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | arxiv=0708.1752| s2cid=18759600 }} Alphecca is believed to be a member of the Ursa Major Moving Group of stars that have a common motion through space.{{cite journal |author1=King, Jeremy R. |author2=Villarreal, Adam R. |author3=Soderblom, David R. |author4=Gulliver, Austin F. |author5=Adelman, Saul J. | title=Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group | journal=The Astronomical Journal | volume=125 | issue=4 | pages=1980–2017 |date=2003 | doi=10.1086/368241 | bibcode=2003AJ....125.1980K| doi-access=free | url=https://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=1248&context=physastro_pubs | url-access=subscription }}

Located 112±3 light-years away, Beta Coronae Borealis or Nusakan is a spectroscopic binary system whose two components are separated by 10 AU and orbit each other every 10.5 years.{{cite web| first1=James B. | last1=Kaler | title=Nusakan | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/nusakan.html | access-date=12 November 2014}} The brighter component is a rapidly oscillating Ap star,{{cite journal|author1=Bruntt, H. |author2=Kervella, P. |author3=Mérand, A. |author4=Brandão, I.M. |author5=Bedding, T.R. |author6=ten Brummelaar, T.A. |author7=Coudé du Foresto, V. |author8=Cunha, M. S. |author9=Farrington, C. |author10=Goldfinger, P.J. |author11=Kiss, L.L. |author12=McAlister, H.A. |author13=Ridgway, S.T. |author14=Sturmann, J. |author15=Sturmann, L. |author16=Turner, N. |author17=Tuthill, P.G. |date=2010|title=The radius and effective temperature of the binary Ap star β CrB from CHARA/FLUOR and VLT/NACO observations|journal=Astronomy and Astrophysics|volume=512|pages=7|id=A55|bibcode=2010A&A...512A..55B|doi=10.1051/0004-6361/200913405|arxiv = 0912.3215 |s2cid=14468327 }} pulsating with a period of 16.2 minutes. Of spectral type A5V with a surface temperature of around 7980 K, it has around {{Solar mass|2.1|link=y}}, 2.6 solar radii ({{Solar radius|link=y}}), and {{Solar luminosity|25.3|link=y}}. The smaller star is of spectral type F2V with a surface temperature of around 6750 K, and has around {{Solar mass|1.4}}, {{Solar radius|1.56}}, and between 4 and {{Solar luminosity|5}}. Near Nusakan is Theta Coronae Borealis, a binary system that shines with a combined magnitude of 4.13 located 380±20 light-years distant. 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.{{cite web| first1=James B. | last1=Kaler | title=Theta Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/thetacrb.html | access-date=12 November 2014}}

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.{{cite web| first1=James B. | last1=Kaler | title=Gamma Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/gammacrb.html | access-date=18 November 2014 | date = 25 July 2008}} The brighter component has been classed as a Delta Scuti variable star,{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=+Gamma+Coronae+Borealis&submit=SIMBAD+search |title = Gamma Coronae Borealis |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 21 November 2014}} though this view is not universal. The components are main sequence stars of spectral types B9V and A3V.{{cite journal|author1=Malkov, O. Yu. |author2=Tamazian, V.S. |author3=Docobo, J. A. |author4=Chulkov, D. A. |date=2012|title=Dynamical Masses of a Selected Sample of Orbital Binaries |journal=Astronomy & Astrophysics |volume=546|id=A69 |pages=5|doi=10.1051/0004-6361/201219774 | bibcode =2012A&A...546A..69M|doi-access=free }} Located 170±2 light-years away, 4.06-magnitude Delta Coronae Borealis is a yellow giant star of spectral type G3.5III that is around {{Solar mass|2.4}} and has swollen to {{Solar radius|7.4}}. It has a surface temperature of 5180 K.{{cite journal|last=Gondoin|first=P.|date=2005|title=The X-ray activity of the slowly rotating G giant δ CrB|journal=Astronomy & Astrophysics|volume=431|issue=3|pages=1027–35| doi= 10.1051/0004-6361:20041991 | bibcode = 2005A&A...431.1027G

|doi-access=free}} 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.{{cite web| first1=James B. | last1=Kaler | title=Delta Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/deltacrb.html | access-date=21 November 2014}}

Zeta Coronae Borealis is a double star with two blue-white components 6.3 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.{{cite book|author1=Kepple, George Robert |author2=Sanner, Glen W. |title=The Night Sky Observers Guide: Spring & summer|publisher=Willmann-Bell|location=Richmond, Virginia|date=1998|pages=111|isbn=978-0-943396-60-6}} 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.{{cite web| first1=James B. | last1=Kaler | title=Nu Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/nucrb.html | access-date=13 November 2014|date=31 August 2007}} The primary, Nu¹ Coronae Borealis, is a red giant of spectral type M2III and magnitude 5.2, lying 640±30 light-years distant,{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+147749&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Nu1 Coronae Borealis |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 13 November 2014}} 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.{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+147767&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Nu2 Coronae Borealis |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 13 November 2014}} Sigma Coronae Borealis, on the other hand, is a true multiple star system divisible by small amateur telescopes.{{sfn|Ridpath|Tirion|2001|pp=126–28}} 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.{{cite journal|author1=Raghavan, Deepak |author2=McAlister, Harold A. |author3=Torres, Guillermo |author4=Latham, David W. |author5=Mason, Brian D. |author6=Boyajian, Tabetha S. |author7=Baines, Ellyn K. |author8=Williams, Stephen J. |author9=ten Brummelaar, Theo A. |author10=Farrington, Chris D. |author11=Ridgway, Stephen T. |author12=Sturmann, Laszlo |author13=Sturmann, Judit |author14=Turner, Nils H. |date=2009|title= The Visual Orbit of the 1.1 Day Spectroscopic Binary σ2 Coronae Borealis from Interferometry at the Chara Array|journal=The Astrophysical Journal|volume=690|issue=1|pages=394–406|doi=10.1088/0004-637X/690/1/394 | bibcode=2009ApJ...690..394R|arxiv = 0808.4015 |s2cid=14638405 }} ADS 9731 is an even rarer multiple system in the constellation, composed of six stars, two of which are spectroscopic binaries.{{cite journal|bibcode=1998AstL...24..795T|title=ADS 9731: A new sextuple system|last1=Tokovinin |first1=A.A.|last2=Shatskii|first2=N.I.|last3=Magnitskii|first3=A.K.|volume=24|issue=6|year=1998|pages=795–801|journal=Astronomy Letters}}{{efn|1=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.}}

Corona Borealis is home to two remarkable variable stars.{{cite book|last=Levy|first=David H.|title=Observing Variable Stars: A Guide for the Beginner|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=1998|pages=142–43|isbn=978-0-521-62755-9|url=https://books.google.com/books?id=5-O2cd937FMC&pg=PA142}} T Coronae Borealis is a cataclysmic variable star also known as the Blaze Star.{{sfn|Ridpath|Tirion|2001|pp=126–128}} 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 T Pyxidis and U Scorpii. An outburst of T Coronae Borealis was first recorded in 1866; its second recorded outburst was in February 1946.{{Cite journal|last=Schaefer |first=Bradley E.

|title=Comprehensive Photometric Histories of All Known Galactic Recurrent Novae

|journal=The Astrophysical Journal Supplement Series

|volume=187

|issue=2

|pages=275–373

|year=2010

|arxiv=0912.4426 |doi=10.1088/0067-0049/187/2/275

|bibcode = 2010ApJS..187..275S |s2cid=119294221

}}{{cite journal

|last=Sanford |first=Roscoe F.

|title=High-Dispersion Spectrograms of T Coronae Borealis.

|journal=Astrophysical Journal

|volume=109 |pages=81 |year=1949

|doi=10.1086/145106

|bibcode=1949ApJ...109...81S|doi-access=

}} 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 was initially expected to go nova at any time between March and September, 2024.{{Cite news

| first = Mia

| last = Taylor

| author-link =

| author =

| author2 =

| title = Move over, solar eclipse: Scientists predict a once-in-a-lifetime nova explosion in the coming months

| url = https://www.bbc.com/future/article/20240322-visible-nova-explosion-is-coming#_msocom_1

| format =

| work =

| publisher = BBC

| pages =

| page =

| date = March 22, 2024

| access-date = March 23, 2024

| language = English

| quote = There's another sign that T CrB is getting ready to blow also, Cooke says. 'We know that before it goes nova it dims for about a year, and T Coronae Borealis started dimming back in March 2023, so that's why we think it's going to go nova between now and the end of September.' As of March 2025, the star has not yet gone nova.

}} 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.{{cite book | last = Levy | first = David H. | year = 2005 | title = Deep Sky Objects | pages = [https://archive.org/details/deepskyobjects00davi/page/70 70–71] | publisher = Prometheus Books | location = Amherst, New York | isbn = 978-1-59102-361-6 | url = https://archive.org/details/deepskyobjects00davi/page/70 }} 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.{{cite web| author=Davis, Kate|date= January 2000 |url=http://www.aavso.org/vsots_rcrb |title= R Coronae Borealis | work=Variable star of the season | publisher= American Association of Variable Star Observers (AAVSO) |access-date=14 March 2015}} 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.{{cite journal|author1=Jeffers, S. V. |author2=Min, M. |author3=Waters, L. B. F. M. |author4=Canovas, H. |author5=Rodenhuis, M. |author6=de Juan Ovelar, M. |author7=Chies-Santos, A. L. |author8=Keller, C. U. |date=2012|title=Direct imaging of a massive dust cloud around R Coronae Borealis|journal=Astronomy & Astrophysics|volume=539|issue=A56|pages=A56|bibcode=2012A&A...539A..56J |doi=10.1051/0004-6361/201117138|arxiv = 1203.1265 |s2cid=55589182 }}

There are several other variables of reasonable brightness for amateur astronomer to observe, including three Mira-type long period variables: S Coronae Borealis ranges between magnitudes 5.8 and 14.1 over a period of 360 days.{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10601 |title=S Coronae Borealis|author=Watson, Christopher|date=4 January 2010|work=The International Variable Star Index|publisher=American Association of Variable Star Observers |access-date=25 September 2014}} 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.{{cite journal|author=McDonald, I.|author2=Zijlstra, A. A.|author3=Boyer, M.L.|date=2012|title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars|journal=Monthly Notices of the Royal Astronomical Society|volume=427|issue=1|pages=343–57|bibcode=2012MNRAS.427..343M|doi=10.1111/j.1365-2966.2012.21873.x|doi-access=free |arxiv = 1208.2037 |s2cid=118665352}} One of the reddest stars in the sky, 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. Varying between magnitudes 6.9 and 12.6 over a period of 357 days,{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10604 |title=V Coronae Borealis|author=Watson, Christopher|date=4 January 2010|work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=13 November 2014}} it is located near the junction of the border of Corona Borealis with Hercules and Bootes. 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.{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10605 |title=W Coronae Borealis|author=Watson, Christopher|date=4 January 2010|work=The International Variable Star Index|publisher=American Association of Variable Star Observers|access-date=9 March 2015}} 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.{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10609 |title=RR Coronae Borealis|author =Otero, Sebastian Alberto |date=15 August 2011 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=25 September 2014}} RS Coronae Borealis is yet another semiregular variable red giant, which ranges between magnitudes 8.7 to 11.6 over 332 days.{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10610 |title=RS Coronae Borealis|author =Watson, Christopher |date=4 January 2010 |work=The International Variable Star Index|publisher=American Association of Variable Star Observers|access-date=25 July 2015}} It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).{{cite journal|author1=Jiménez-Esteban, F. M. |author2=Caballero, J. A. |author3=Dorda, R. |author4=Miles-Páez, P. A. |author5=Solano, E. |date=2012|title=Identification of red high proper-motion objects in Tycho-2 and 2MASS catalogues using Virtual Observatory tools|journal=Astronomy & Astrophysics|volume=539|pages=12|doi=10.1051/0004-6361/201118375 |bibcode=2012A&A...539A..86J|arxiv = 1201.5315 |s2cid=53404166 }} 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{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10603 |title=U Coronae Borealis|author=Watson, Christopher |date=4 January 2010|work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=10 March 2015}}

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.{{cite journal|author1=Romero, A. D. |author2=Córsico, A. H. |author3=Althaus, L. G. |author4-link=Kepler de Souza Oliveira |author4=Kepler, S. O. |author5=Castanheira, B. G. |author6=Miller Bertolami, M. M. |date=2012|title=Toward ensemble asteroseismology of ZZ Ceti stars with fully evolutionary models|journal=Monthly Notices of the Royal Astronomical Society|volume=420|issue=2|pages=1462–80| doi=10.1111/j.1365-2966.2011.20134.x |doi-access=free |bibcode=2012MNRAS.420.1462R|arxiv = 1109.6682 |s2cid=55018129 }} 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.{{cite journal|author1=Mason, Paul A. |author2=Robinson, Edward L. |author3=Bayless, Amanda J. |author4=Hakala, Pasi J. |date=2012|title=Long-term Optical Observations of Two LMXBS: UW CrB (=MS 1603+260) and V1408 Aql (=4U 1957+115)|journal=The Astronomical Journal|volume=144|issue=4|pages=108 |doi=10.1088/0004-6256/144/4/108 |bibcode=2012AJ....144..108M|hdl=2152/34339 |s2cid=122184568 |hdl-access=free }}

Extrasolar planets have been confirmed in five star systems, four of which were found by the radial velocity method. The spectrum of Epsilon Coronae Borealis was analysed for seven years from 2005 to 2012, revealing a planet around 6.7 times as massive as Jupiter ({{Jupiter mass|link=y}}) orbiting every 418 days at an average distance of around 1.3 AU.{{cite journal|author1=Lee, B.-C. |author2=Han, I. |author3=Park, M.-G. |author4=Mkrtichian, D. E. |author5=Kim, K.-M. |date=2012|title=A planetary companion around the K giant ɛ Corona Borealis|journal=Astronomy & Astrophysics|volume=546|id=A5|pages=5|bibcode=2012A&A...546A...5L|doi=10.1051/0004-6361/201219347|arxiv = 1209.1187 |s2cid=55260442 }} Epsilon itself is a {{Solar mass|1.7}} orange giant of spectral type K2III that has swollen to {{Solar radius|21}} and {{Solar luminosity|151}}.{{cite journal | last1=Massarotti | first1=Alessandro | last2=Latham | first2=David W. | last3=Stefanik | first3=Robert P. | last4=Fogel | first4=Jeffrey | s2cid=121883397 | title=Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity | journal=The Astronomical Journal | volume=135 | issue=1 | pages=209–31 |date=January 2008 | doi=10.1088/0004-6256/135/1/209 | bibcode=2008AJ....135..209M | doi-access=free }} Kappa Coronae Borealis is a spectral type K1IV orange subgiant nearly twice as massive as the Sun; around it lies a dust debris disk, and one planet with a period of 3.4 years.{{cite journal |journal=Publications of the Astronomical Society of Japan | volume = 64 |issue = 6 |id=135 |pages= 14 |title=Substellar Companions to Seven Evolved Intermediate-Mass Stars |arxiv=1207.3141 |year=2012 |author1=Sato, Bun'ei |author2=Omiya, Masashi |author3=Harakawa, Hiroki |author4=Izumiura, Hideyuki |author5=Kambe, Eiji |author6=Takeda, Yoichi |author7=Yoshida, Michitoshi |author8=Itoh, Yoichi |author9=Ando, Hiroyasu |author10=Kokubo, Eiichiro |author11=Ida, Shigeru |bibcode = 2012PASJ...64..135S |doi = 10.1093/pasj/64.6.135| s2cid = 119197073 }} This planet's mass is estimated at {{Jupiter mass|2.5|link=y}}. The dimensions of the debris disk indicate it is likely there is a second substellar companion.{{cite journal |author1=Bonsor, Amy |author2=Kennedy, Grant M. |author3=Crepp, Justin R. |author4=Johnson, John A. |author5=Wyatt, Mark C. |author6=Sibthorpe, Bruce |author7=Su, Kate Y. L. |year=2013 |title=Spatially Resolved Images of Dust Belt(s) Around the Planet-hosting Subgiant κ CrB |journal=MNRAS |volume=431 |issue= 4|pages=3025–3035 |doi=10.1093/mnras/stt367 |doi-access=free |arxiv = 1302.7000 |bibcode = 2013MNRAS.431.3025B |s2cid=27703182 }} Omicron Coronae Borealis is a K-type clump giant with one confirmed planet with a mass of {{Jupiter mass|0.83}} that orbits every 187 days—one of the two least massive planets known around clump giants. HD 145457 is an orange giant of spectral type K0III found to have one planet of {{Jupiter mass|2.9}}. Discovered by the Doppler method in 2010, it takes 176 days to complete an orbit.{{cite journal|author1=Sato, Bun'ei |author2=Omiya, Masashi |author3=Liu, Yujuan |author4=Harakawa, Hiroki |author5=Izumiura, Hideyuki |author6=Kambe, Eiji |author7=Toyota, Eri |author8=Murata, Daisuke |author9=Lee, Byeong-Cheol |author10=Masuda, Seiji |author11=Takeda, Yoichi |author12=Yoshida, Michitoshi |author13=Itoh, Yoichi |author14=Ando, Hiroyasu |author15=Kokubo, Eiichiro |author16=Ida, Shigeru |author17=Zhao, Gang |author18=Han, Inwoo |date=2010|title=Substellar Companions to Evolved Intermediate-Mass Stars: HD 145457 and HD 180314|journal=Publications of the Astronomical Society of Japan|volume=62|issue=4|pages=1063–69|bibcode=2010PASJ...62.1063S|doi=10.1093/pasj/62.4.1063|arxiv = 1005.2860 |s2cid=119113950 }} XO-1 is a magnitude 11 yellow main-sequence star located approximately {{convert|172|pc|ly|disp=output number only}} light-years away,{{cite journal | title=Improved Parameters for Extrasolar Transiting Planets | last1=Torres | first1=Guillermo | last2=Winn | first2=Joshua N. | last3=Holman | first3=Matthew J. | journal=The Astrophysical Journal | volume=677 | issue=2 | pages=1324–42 | year=2008 | arxiv=0801.1841 | bibcode=2008ApJ...677.1324T | doi=10.1086/529429 | s2cid=12899134 }} of spectral type G1V with a mass and radius similar to the Sun. In 2006 the hot Jupiter exoplanet XO-1b was discovered orbiting XO-1 by the transit method using the XO Telescope. Roughly the size of Jupiter, it completes an orbit around its star every three days.{{cite journal | title=A Transiting Planet of a Sun-like Star | last1=McCullough | first1=P. R. | last2=Stys | first2=J. E. | last3=Valenti | first3=Jeff A. | last4=Johns-krull | first4=C. M. | last5=Janes | first5=K.A. | last6=Heasley | first6=J. N. | last7=Bye | first7=B. A. | last8=Dodd | first8=C. | last9=Fleming | first9=S. W. | last10=Pinnick | first10=A. | last11=Bissinger | first11=R. | last12=Gary | first12=B. L. | last13=Howell | first13=P. J. | last14=Vanmunster | first14=T. | journal=The Astrophysical Journal | volume=648 | issue=2 | pages=1228–38 | year=2006 | arxiv=astro-ph/0605414 | bibcode=2006ApJ...648.1228M | doi=10.1086/505651| s2cid=8100425 }}

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 Solar analog of spectral type G0V,{{cite journal | author=van Belle, Gerard T. | author2=von Braun, Kaspar | title=Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars | journal=The Astrophysical Journal | volume=694 | issue=2 | date=2009 | pages=1085–98| doi=10.1088/0004-637X/694/2/1085 | bibcode=2009ApJ...694.1085V|arxiv = 0901.1206 | s2cid=18370219 }} around 57 light-years distant from Earth.{{cite journal|author1=Noyes, Robert W. |author2=Jha, Saurabh |author3=Korzennik, Sylvain G. |author4=Krockenberger, Martin |author5=Nisenson, Peter |author6=Brown, Timothy M. |author7=Kennelly, Edward J. |author8=Horner, Scott D. |title=A Planet Orbiting the Star ρ Coronae Borealis|year=1997|journal=The Astrophysical Journal|volume=483|issue=2|pages=L111–14|doi=10.1086/310754|bibcode=1997ApJ...483L.111N|arxiv = astro-ph/9704248 |s2cid=115606006 }} More accurate measurement of data from the Hipparcos satellite subsequently showed it instead to be a low-mass star somewhere between 100 and 200 times the mass of Jupiter.{{cite journal|author1=Reffert, S. |author2=Quirrenbach, A. |title=Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: nine confirmed planets and two confirmed brown dwarfs|year=2011|journal=Astronomy & Astrophysics|volume=527|pages=A140|doi=10.1051/0004-6361/201015861|bibcode=2011A&A...527A.140R|arxiv=1101.2227|s2cid=54986291 }} Possible stable planetary orbits in the habitable zone were calculated for the binary star Eta Coronae Borealis,{{cite journal|last=Benest|first=D.|date=1996|title= Planetary orbits in the elliptic restricted problem. III. The η Coronae Borealis system.|journal=Astronomy and Astrophysics|volume=314|pages=983–88|bibcode=1996A&A...314..983B}} 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.{{cite web| first1=James B. | last1=Kaler | title=Eta Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/etacrb.html | date =22 June 2012 | access-date=16 March 2015}} 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.{{cite journal | title=Brown Dwarf Companions to G-Type Stars. I. Gliese 417B and Gliese 584C | journal=The Astronomical Journal | volume=121 | issue=6 | pages=3235–3253 |author1=Kirkpatrick, J. Davy |author2=Dahn, Conard C. |author3=Monet, David G. |author4=Reid, I. Neill |author5=Gizis, John E. |author6=Liebert, James |author7=Burgasser, Adam J. | year=2001 | arxiv=astro-ph/0103218 |bibcode=2001AJ....121.3235K |doi = 10.1086/321085 | s2cid=18515414 }}

File:Abell2142 chandra xray.jpg]]

Corona Borealis contains few galaxies observable with amateur telescopes.{{cite book|last=Luginbuhl|first=Christian B. |author2=Skiff, Brian A. |title=Observing Handbook and Catalogue of Deep-Sky Objects|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=1998|pages=92|isbn=978-0-521-62556-2|url=https://books.google.com/books?id=MwCyjQpGU7UC&pg=PA92}} NGC 6085 and 6086 are a faint spiral and elliptical galaxy respectively close enough to each other to be seen in the same visual field through a telescope.{{cite book|last=Rumistrzewicz|first=Stefan |title=A Visual Astronomer's Photographic Guide to the Deep Sky: A Pocket Field Guide|publisher=Springer Science & Business Media|location=New York, New York|date=2010|pages=158|isbn=978-1-4419-7242-2|url=https://books.google.com/books?id=Vhjn3DEJpyIC&pg=PA158}} Abell 2142 is a huge (six million light-year diameter), X-ray luminous galaxy cluster that is the result of an ongoing merger between two galaxy clusters. It has a redshift of 0.0909 (meaning it is moving away from us at 27,250 km/s) and a visual magnitude of 16.0. It is about 1.2 billion light-years away.{{efn|1=Distance calculated from redshift.}}{{cite web | title= NASA/IPAC Extragalactic Database | work= Results for Abell 2142 | url= http://nedwww.ipac.caltech.edu/ | access-date = 11 Nov 2008 | archive-url= https://web.archive.org/web/20081216032441/http://nedwww.ipac.caltech.edu/| archive-date= 16 December 2008 | url-status= live}} Another galaxy cluster in the constellation, RX J1532.9+3021, is approximately 3.9 billion light-years from Earth.{{cite web | url =http://chandra.harvard.edu/photo/2014/rxj1532/| title =RX J1532.9+3021: Extreme Power of Black Hole Revealed |publisher =Chandra X-ray Center|date=January 23, 2014| access-date =27 January 2014 }} At the cluster's center is a large elliptical galaxy containing one of the most massive and most powerful supermassive black holes yet discovered. 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.{{sfn|Ridpath|Tirion|2001|pp=126–128}} 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.{{cite journal |title=The dynamics of the Corona Borealis supercluster |author1=Postman, M. |author2=Geller, M. J. |author3=Huchra, J. P. |journal=Astronomical Journal | volume= 95 |year= 1988 |pages= 267–83 |doi=10.1086/114635 |bibcode=1988AJ.....95..267P}} Another galaxy cluster, Abell 2162, is a member of the Hercules Superclusters.{{cite journal|author1=Kopylova, F. G. |author2=Kopylov, A. I. |date=2013|title=Investigation of properties of galaxy clusters in the Hercules supercluster region|journal=Astronomy Letters|volume=39|issue=1|pages=1–16|doi=10.1134/S1063773712120043 | bibcode= 2013AstL...39....1K |s2cid=120136802 }}{{Clear}}

File:Sidney Hall - Urania's Mirror - Hercules and Corona Borealis.jpg and Corona Borealis, as depicted in Urania's Mirror ({{circa|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.{{sfn|Ridpath|Tirion|2001|pp=126–128}} 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. {{lang|la|De astronomia}}, attributed to 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. Its proximity to the constellations Hercules (which {{lang|la|De astronomia}} reports was once attributed to Theseus, among others) and Lyra (Theseus' lyre in one account) could indicate that the three constellations were invented as a group.{{cite book | translator-first=Robin | translator-last=Hard | chapter=Hercules, originally known as Engonasin, the Kneeler | title=Constellation Myths | year=2015 | isbn=9780191026539 | publisher=Oxford University Press }} Corona Borealis was one of the 48 constellations mentioned in the Almagest of classical astronomer Ptolemy.

In Mesopotamia, Corona Borealis was associated with the goddess Nanaya.M. Stol, Nanaja [in:] [http://publikationen.badw.de/en/rla/index Reallexikon der Assyriologie und vorderasiatischen Archäologie] vol 9, 1998, p. 147

In Welsh mythology, it was called Caer Arianrhod, "the Castle of the Silver Circle", and was the heavenly abode of the Lady Arianrhod.{{cite book| last1 = Squire | first1 = Charles L. |pages=154–55 | year = 2000 | title = The Mythology of the British Islands | publisher = Wordsworth Editions Ltd |location = Ware, United Kingdom | isbn = 978-1-84022-500-6}} To the ancient Balts, Corona Borealis was known as Darželis, the "flower garden".{{cite journal | title=The Cosmology of the Ancient Balts |author1=Straižys, V. |author2=Klimka, L. | journal=Journal for the History of Astronomy, Archaeoastronomy Supplement | volume= 28|issue=22 |page=S57 |bibcode=1997JHAS...28...57S | doi=10.1177/002182869702802207|year=1997 |s2cid=117470993 }}

The Arabs called the constellation Alphecca (a name later given to Alpha Coronae Borealis), which means "separated" or "broken up" ({{lang|ar|الفكة}} {{Transliteration|ar|al-Fakkah}}), a reference to the resemblance of the stars of Corona Borealis to a loose string of jewels.{{cite book|author1=Kunitzch, Paul |author2=Smart, Tim | title=A Dictionary of Modern Star Names: A Short Guide to 254 Star Names and Their Derivations |page=30 |year=2006 | publisher=Sky Publishing Corporation |location=Cambridge, Massachusetts |isbn=978-1-931559-44-7 | orig-year=1986}} This was also interpreted as a broken dish.{{cite book|last=Raymo|first=Chet |title=Three Hundred and Sixty Five Starry Nights: An Introduction to Astronomy for Every Night of the Year|publisher=Simon and Schuster|location=New York, New York|date=1990|orig-year=1982|page=101|isbn=978-0-671-76606-1|url=https://books.google.com/books?id=rTe5HaRsAS4C&pg=PA101}} Among the Bedouins, the constellation was known as {{Transliteration|ar|DIN|qaṣʿat al-masākīn}} ({{lang|ar|قصعة المساكين}}), or "the dish/bowl of the poor people".{{cite book|title=An Eleventh-Century Egyptian Guide to the Universe: The Book of Curiosities, Edited with an Annotated Translation|url=https://books.google.com/books?id=ERJMAgAAQBAJ&pg=PA622|author1=Rapoport, Yossef |author2=Savage-Smith, Emilie | publisher=BRILL|location= Leiden, Netherlands|isbn=978-90-04-25699-6|page=622|date=2013}}

The Skidi people of Native Americans saw the stars of Corona Borealis representing a council of stars whose chief was Polaris.{{cite journal|last=Hall|first=Robert L.|date=2005|title=Contradictions as a Source of Historical Perspective: Camp Circles and Sacred Poles|journal=Ontario Archaeology|issue=79/80|pages=115–26 [122]|url=http://www.ontarioarchaeology.on.ca/publications/pdf/oa_79-80hall.pdf |archive-url=https://web.archive.org/web/20150227150425/http://www.ontarioarchaeology.on.ca/publications/pdf/oa_79-80hall.pdf |archive-date=2015-02-27 |url-status=live}} 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.{{cite book|last=Chamberlain|first=Von Del|title=Archaeoastronomy in the New World: American Primitive Astronomy : Proceedings of an International Conference Held at Oxford University, September, 1981|editor=Anthony F. Aveni|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=1982|pages=184|chapter=Earth Lodge as Observatory|isbn=978-0-521-24731-3}} 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. The Mi'kmaq of eastern Canada saw Corona Borealis as Mskegwǒm, the den of the celestial bear (Alpha, Beta, Gamma and Delta Ursae Majoris).{{cite journal|last=Hagar|first=Stansbury |date=1900|title=The Celestial Bear|journal=The Journal of American Folklore|volume=13|issue=49|pages=92–103|jstor=533799|doi=10.2307/533799}}

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.{{cite book| last = Makemson | first = Maud Worcester |page=282| year = 1941 | publisher = Yale University Press |location = New Haven, Connecticut | title = The Morning Star Rises: an account of Polynesian astronomy| bibcode = 1941msra.book.....M }}

In Australian Aboriginal astronomy, the constellation is called womera ("the boomerang") due to the shape of the stars.{{cite book| page= 151 |url=https://books.google.com/books?id=TIatz2DGXQwC |title=Star Lore: Myths, Legends, and Facts|author=Olcott, William Tyler |location= New York, New York |publisher = Dover Publication Inc.|isbn=978-0-486-43581-7|year= 2004}} 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.{{cite book|last=Ridley|first=William|title=Kámilarói, and other Australian languages|publisher=T. Richards, government printer|location=Sydney, New South Wales|year=1875|edition=2nd|pages=141–42}} 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.{{cite book | last1 = Harney | first1 = Bill Yidumduma | last2 = Cairns | first2 = Hugh C. | title = Dark Sparklers | publisher = Hugh C. Cairns | location = Merimbula, New South Wales |pages=98, 105 | year = 2004 | orig-year = 2003 | edition = Revised | isbn = 0-9750908-0-1}}

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.{{cite book | first=Nick | last=Kanas | date=2007 | title=Star maps: history, artistry, and cartography | pages=207–09 |url=https://books.google.com/books?id=bae3LP4tfP4C&pg=PA208 | publisher=Springer |location=New York, New York | isbn=978-0-387-71668-8 }} The constellation was featured as a main plot ingredient in the short story "Hypnos" by H. P. Lovecraft, published in 1923; it is the object of fear of one of the protagonists in the short story.{{cite book|last=Smith|first=Don G. |title=H.P. Lovecraft in Popular Culture: The Works and Their Adaptations in Film, Television, Comics, Music and Games|publisher=McFarland|location=Jefferson, North Carolina|date=2005|pages=16|isbn=0-7864-2091-X|url=https://books.google.com/books?id=3jTFK9HTZaUC&pg=PA16}} Finnish band Cadacross released an album titled Corona Borealis in 2002.{{cite web|url=http://www.allmusic.com/album/corona-borealis-mw0000335058|title=Cadacross Corona Borealis|work=Allmusic|date=2015|publisher=All Media Network|access-date=14 March 2015}}

• Corona Borealis (Chinese astronomy)

{{notelist}}

{{reflist}}

• {{cite book | last1 = Ridpath | first1 = Ian | last2 = Tirion | first2 = Wil | year = 2001 | title = Stars and Planets Guide | publisher = Princeton University Press |location = Princeton, New Jersey | isbn = 978-0-691-08913-3 }}

• {{Commons-inline}}
• [https://iconographic.warburg.sas.ac.uk/category/vpc-taxonomy-017043 Warburg Institute Iconographic Database (ca 160 medieval and early modern images of Corona Borealis)]

{{Stars of Corona Borealis}}

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Category:Ariadne

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Category:Northern constellations

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