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Created page with "{{Night Sky | image = | designation =Alphecca<br/>α Coronae Borealis<br/>5 Coronae Borealis | rightascension =15<sup>h</sup> 34<sup>m</sup> 41.2680<sup>s</sup>..."
{{Night Sky
| image =
| designation =Alphecca<br/>α Coronae Borealis<br/>5 Coronae Borealis
| rightascension =15<sup>h</sup> 34<sup>m</sup> 41.2680<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Alpha+Coronae+Borealis&submit=SIMBAD+search Alpha Coronae Borealis] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref><ref name=hip>
{{cite journal
|last1=van Leeuwen |first1=F.
|title=Validation of the new Hipparcos reduction
|journal=Astronomy & Astrophysics
|volume=474
|issue=2|page=653-664|date=2007
|doi=10.1051/0004-6361:20078357
|bibcode=2007A&A...474..653V
|ref=harv
}} {{arXiv|0708.1752}}
</ref>
| declination =+26° 42′ 52.8940″<ref name=simbad/><ref name=hip/>
| distance =75 ly<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/constellation-list/corona-borealis-constellation/|title=Corona Borealis Constellation|accessdate=2019-04-13|publisher=constellation-guide.com}}</ref>
| constellation =Corona Borealis
| type =Main sequence star
| dimensions =
| magnitude =Apparent Mag: +2.22<ref name=universeguide>{{cite web|url=https://www.universeguide.com/star/alphecca|title=Alphecca (Alpha Coronae Borealis, 5 Coronae Borealis)|accessdate=2019-04-13|publisher=universeguide.com}}</ref><br/>Absolute Mag: 0.41<ref name=universeguide/>
| redshift =
| radvelocity =1.7±0.9 km/s<ref name=simbad/><ref>Wilson, R. (1953). General catalogue of stellar radial velocities. ''Carnegie Institute Washington D.C. Publication''. [https://ui.adsabs.harvard.edu/#abs/1953GCRV..C......0W/abstract Bibcode:1953GCRV..C......0W]</ref>
| propmotion =RA: 120.27 mas/yr<ref name=simbad/><ref name=hip/><br/>Dec.: -89.58 mas/yr<ref name=simbad/><ref name=hip/>
| parallax =43.46±0.28 mas<ref name=simbad/><ref name=hip/>
}}
'''Alpha Coronae Borealis''' (Alphecca, α Coronae Borealis, α CrB, 5 Coronae Borealis) is a [[main sequence star]] in the [[constellation]] of [[Corona Borealis]], the Northern Crown.<ref name=constellation-guide/> The star is known by several names: Alphecca (which roughly translates as “the bright one of the broken ring” in [[Arabic]]), Gemma (“jewel” in [[Latin]]), Asteroth (“idols” in [[Hebrew]]), and Gnosia (short for “Gnosia stella coronae,” or “the star of the crown of Knossos” in Latin).<ref name=constellation-guide/> The star is in fact one star in a [[binary star|binary system]] of two stars. The brightest star in the Northern Crown, it was first catalogued in the 2nd century by the [[Ancient Greece|Greek]] astronomer, [[Ptolemy]].<ref name=osr>{{cite web|url=https://osr.org/blog/astronomy/alpha-coronae-borealis/|title=Alpha Coronae Borealis – Star Facts|accessdate=2019-04-13|publisher=osr.org|date=2016-06-01}}</ref> The star is bright enough to be seen with the unaided eye and is best observed in the mid-northern latitudes between April, May and June. It can be found by drawing an imaginairy line from [[Arcturus]] to [[Vega]].
Situated approximately 75 [[light year]]s from [[Earth]], Alpha Coronae Borealis a white star belonging to [[spectral type|spectral class]] A0V.<ref name=osr/> Its [[spectrum]] shows a large excess of [[infrared|infrared radiation]], thought to be caused by a disk of dust and other material surrounding the star. Such a disc may contain [[planet]]s. The star is 67 times more luminous than the [[Sun]] and possess a radius 2.7 times as large.<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/alphecca.html|title=ALPHECCA|accessdate=2019-04-13|publisher=stars.astro.illinois.edu|work=Stars|author=Jim Kaler}}</ref> Its mass is estimated at 2.7 [[solar mass]]es and it has a high surface temperature of 10,000 kelvin.<ref name=illinois/> The star rotates quickly, with a speed of 110 km/s, though other sources put it higher at 127-133&nsbp;km/s.<ref>
{{cite journal
|last1=Royer |first1=F.
|last2=Gerbaldi |first2=M.
|last3=Faraggiana |first3=R.
|last4=Gómez |first4=A. E.
|display-authors=3
|title=Rotational velocities of A-type stars. I. Measurement of v sin i in the southern hemisphere
|journal=Astronomy and Astrophysics
|volume=381
|page=105-121|date=2002
|doi=10.1051/0004-6361:20011422
|bibcode=2002A&A...381..105R
|ref=harv
}} {{arXiv|astro-ph/0205255}}
</ref><ref name=illinois/>
Alpha Coronae Borealis is part of a binary system and orbits its companion star every 17.3599 days.<ref name=constellation-guide/><ref>
{{cite journal
|last1=Schmitt |first1=J. H. M. M.
|last2=Schröder |first2=K.-P.
|last3=Rauw |first3=G.
|last4=Hempelmann |first4=A.
|last5=Mittag |first5=M.
|last6=González-Pérez |first6=J. N.
|last7=Czesla |first7=S.
|last8=Wolter |first8=U.
|last9=Jack |first9=D.
|display-authors=3
|title=The α CrB binary system: A new radial velocity curve, apsidal motion, and the alignment of rotation and orbit axes
|journal=Astronomy & Astrophysics
|volume=586
|issue=A104|page=13|date=2016
|doi=10.1051/0004-6361/201526662
|bibcode=2016A&A...586A.104S
|ref=harv
}}
</ref> Alpha Coronae Borealis is sometimes referred to as Alphecca-A to distinguish it from the system or the companion which is then designated Alphecca-B. The average separation between the stars is 0.20 [[AU]] (smaller than the distance between the Sun and [[Mercury]]), though the [[eccentricity]] of the [[orbit]] of ''e''=0.35 means it varies from 0.13&nsbp;AU up to 0.27&nsbp;AU.<ref name=illinois/><ref>Eccentricity computed using ''a''<sub>min</sub>=(1-''e'')''a'', with ''a''<sub>min</sub>=0.13&nsbp;AU, ''a''=0.2 AU.</ref> These two stars are believed to be part of the Ursa Major Moving Group, a collection of stars in [[Ursa Major]] that share a common motion through space.
Alphecca-B is a main sequence star with spectral class G5 and is an 8<sup>th</sup> magnitude star, too dim to be seen with the naked eye.<ref>{{cite web|url=http://www.constellationsofwords.com/stars/Alphecca.html|title=Alphecca|accessdate=2019-04-13|publisher=constellationsofwords.com}}</ref> The system is classified as an [[variable star|EA variable]], meaning the brightness of Alpha Coronae Borealis varies as it is eclipsed by its companion from +2.21 up to +2.32.<ref name=constellation-guide/> The companion star is smaller than Alpha Coronae Borealis with a mass of 0.92 [[solar mass]]es and radius of 0.9 that of Sol.<ref name=osr/> Alphecca-B is a powerful [[x-ray]] source, though to be caused by "solar-like magnetic activity".<ref name=illinois/>
Images taken by the [[Hubble Space Telescope]] have shown a disk of material that lies in the same plane as the [[orbit]] of the two stars.<ref>
{{cite journal
|last1=Kennedy |first1=G. M.
|last2=Wyatt |first2=M. C.
|last3=Sibthorpe |first3=B.
|last4=Phillips |first4=N. M.
|last5=Matthews |first5=B. C.
|last6=Greaves |first6=J. S.
|display-authors=3
|title=Coplanar Circumbinary Debris Disks
|journal=Monthly Notices of the Royal Astronomical Society
|volume=426
|issue=3|page=2115-2128|date=2012
|doi=10.1111/j.1365-2966.2012.21865.x
|bibcode=2012MNRAS.426.2115K
|ref=harv
}} {{arXiv|1208.1759}}
</ref>
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Stars]]
| image =
| designation =Alphecca<br/>α Coronae Borealis<br/>5 Coronae Borealis
| rightascension =15<sup>h</sup> 34<sup>m</sup> 41.2680<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Alpha+Coronae+Borealis&submit=SIMBAD+search Alpha Coronae Borealis] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref><ref name=hip>
{{cite journal
|last1=van Leeuwen |first1=F.
|title=Validation of the new Hipparcos reduction
|journal=Astronomy & Astrophysics
|volume=474
|issue=2|page=653-664|date=2007
|doi=10.1051/0004-6361:20078357
|bibcode=2007A&A...474..653V
|ref=harv
}} {{arXiv|0708.1752}}
</ref>
| declination =+26° 42′ 52.8940″<ref name=simbad/><ref name=hip/>
| distance =75 ly<ref name=constellation-guide>{{cite web|url=https://www.constellation-guide.com/constellation-list/corona-borealis-constellation/|title=Corona Borealis Constellation|accessdate=2019-04-13|publisher=constellation-guide.com}}</ref>
| constellation =Corona Borealis
| type =Main sequence star
| dimensions =
| magnitude =Apparent Mag: +2.22<ref name=universeguide>{{cite web|url=https://www.universeguide.com/star/alphecca|title=Alphecca (Alpha Coronae Borealis, 5 Coronae Borealis)|accessdate=2019-04-13|publisher=universeguide.com}}</ref><br/>Absolute Mag: 0.41<ref name=universeguide/>
| redshift =
| radvelocity =1.7±0.9 km/s<ref name=simbad/><ref>Wilson, R. (1953). General catalogue of stellar radial velocities. ''Carnegie Institute Washington D.C. Publication''. [https://ui.adsabs.harvard.edu/#abs/1953GCRV..C......0W/abstract Bibcode:1953GCRV..C......0W]</ref>
| propmotion =RA: 120.27 mas/yr<ref name=simbad/><ref name=hip/><br/>Dec.: -89.58 mas/yr<ref name=simbad/><ref name=hip/>
| parallax =43.46±0.28 mas<ref name=simbad/><ref name=hip/>
}}
'''Alpha Coronae Borealis''' (Alphecca, α Coronae Borealis, α CrB, 5 Coronae Borealis) is a [[main sequence star]] in the [[constellation]] of [[Corona Borealis]], the Northern Crown.<ref name=constellation-guide/> The star is known by several names: Alphecca (which roughly translates as “the bright one of the broken ring” in [[Arabic]]), Gemma (“jewel” in [[Latin]]), Asteroth (“idols” in [[Hebrew]]), and Gnosia (short for “Gnosia stella coronae,” or “the star of the crown of Knossos” in Latin).<ref name=constellation-guide/> The star is in fact one star in a [[binary star|binary system]] of two stars. The brightest star in the Northern Crown, it was first catalogued in the 2nd century by the [[Ancient Greece|Greek]] astronomer, [[Ptolemy]].<ref name=osr>{{cite web|url=https://osr.org/blog/astronomy/alpha-coronae-borealis/|title=Alpha Coronae Borealis – Star Facts|accessdate=2019-04-13|publisher=osr.org|date=2016-06-01}}</ref> The star is bright enough to be seen with the unaided eye and is best observed in the mid-northern latitudes between April, May and June. It can be found by drawing an imaginairy line from [[Arcturus]] to [[Vega]].
Situated approximately 75 [[light year]]s from [[Earth]], Alpha Coronae Borealis a white star belonging to [[spectral type|spectral class]] A0V.<ref name=osr/> Its [[spectrum]] shows a large excess of [[infrared|infrared radiation]], thought to be caused by a disk of dust and other material surrounding the star. Such a disc may contain [[planet]]s. The star is 67 times more luminous than the [[Sun]] and possess a radius 2.7 times as large.<ref name=illinois>{{cite web|url=http://stars.astro.illinois.edu/sow/alphecca.html|title=ALPHECCA|accessdate=2019-04-13|publisher=stars.astro.illinois.edu|work=Stars|author=Jim Kaler}}</ref> Its mass is estimated at 2.7 [[solar mass]]es and it has a high surface temperature of 10,000 kelvin.<ref name=illinois/> The star rotates quickly, with a speed of 110 km/s, though other sources put it higher at 127-133&nsbp;km/s.<ref>
{{cite journal
|last1=Royer |first1=F.
|last2=Gerbaldi |first2=M.
|last3=Faraggiana |first3=R.
|last4=Gómez |first4=A. E.
|display-authors=3
|title=Rotational velocities of A-type stars. I. Measurement of v sin i in the southern hemisphere
|journal=Astronomy and Astrophysics
|volume=381
|page=105-121|date=2002
|doi=10.1051/0004-6361:20011422
|bibcode=2002A&A...381..105R
|ref=harv
}} {{arXiv|astro-ph/0205255}}
</ref><ref name=illinois/>
Alpha Coronae Borealis is part of a binary system and orbits its companion star every 17.3599 days.<ref name=constellation-guide/><ref>
{{cite journal
|last1=Schmitt |first1=J. H. M. M.
|last2=Schröder |first2=K.-P.
|last3=Rauw |first3=G.
|last4=Hempelmann |first4=A.
|last5=Mittag |first5=M.
|last6=González-Pérez |first6=J. N.
|last7=Czesla |first7=S.
|last8=Wolter |first8=U.
|last9=Jack |first9=D.
|display-authors=3
|title=The α CrB binary system: A new radial velocity curve, apsidal motion, and the alignment of rotation and orbit axes
|journal=Astronomy & Astrophysics
|volume=586
|issue=A104|page=13|date=2016
|doi=10.1051/0004-6361/201526662
|bibcode=2016A&A...586A.104S
|ref=harv
}}
</ref> Alpha Coronae Borealis is sometimes referred to as Alphecca-A to distinguish it from the system or the companion which is then designated Alphecca-B. The average separation between the stars is 0.20 [[AU]] (smaller than the distance between the Sun and [[Mercury]]), though the [[eccentricity]] of the [[orbit]] of ''e''=0.35 means it varies from 0.13&nsbp;AU up to 0.27&nsbp;AU.<ref name=illinois/><ref>Eccentricity computed using ''a''<sub>min</sub>=(1-''e'')''a'', with ''a''<sub>min</sub>=0.13&nsbp;AU, ''a''=0.2 AU.</ref> These two stars are believed to be part of the Ursa Major Moving Group, a collection of stars in [[Ursa Major]] that share a common motion through space.
Alphecca-B is a main sequence star with spectral class G5 and is an 8<sup>th</sup> magnitude star, too dim to be seen with the naked eye.<ref>{{cite web|url=http://www.constellationsofwords.com/stars/Alphecca.html|title=Alphecca|accessdate=2019-04-13|publisher=constellationsofwords.com}}</ref> The system is classified as an [[variable star|EA variable]], meaning the brightness of Alpha Coronae Borealis varies as it is eclipsed by its companion from +2.21 up to +2.32.<ref name=constellation-guide/> The companion star is smaller than Alpha Coronae Borealis with a mass of 0.92 [[solar mass]]es and radius of 0.9 that of Sol.<ref name=osr/> Alphecca-B is a powerful [[x-ray]] source, though to be caused by "solar-like magnetic activity".<ref name=illinois/>
Images taken by the [[Hubble Space Telescope]] have shown a disk of material that lies in the same plane as the [[orbit]] of the two stars.<ref>
{{cite journal
|last1=Kennedy |first1=G. M.
|last2=Wyatt |first2=M. C.
|last3=Sibthorpe |first3=B.
|last4=Phillips |first4=N. M.
|last5=Matthews |first5=B. C.
|last6=Greaves |first6=J. S.
|display-authors=3
|title=Coplanar Circumbinary Debris Disks
|journal=Monthly Notices of the Royal Astronomical Society
|volume=426
|issue=3|page=2115-2128|date=2012
|doi=10.1111/j.1365-2966.2012.21865.x
|bibcode=2012MNRAS.426.2115K
|ref=harv
}} {{arXiv|1208.1759}}
</ref>
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Stars]]