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'''Sigma Coronae Borealis''' is a multiple star system in the constellation ], the main components of which are three sunlike stars.<ref name=kalersigma>{{cite web| first1=James B. | last1=Kaler | title=Sigma Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/sigmacrb.html | accessdate=23 November 2014}}</ref> Appearing as a single star of apparent magnitude 5.3 to the unaided eye, Sigma can be separated into 6.6-magnitude Sigma<sup>1</sup> and 5.64-magnitude Sigma<sup>2</sup> when observed with a telescope.<ref name=kalersigma/> The two take 726 years to orbit each other.<ref name="Raghavan 2009">{{cite journal|last=Raghavan, Deepak; McAlister, Harold A.; Torres, Guillermo; Latham, David W.; Mason, Brian D.; Boyajian, Tabetha S.; Baines, Ellyn K.; Williams, Stephen J.; ten Brummelaar, Theo A.; Farrington, Chris D.; Ridgway, Stephen T.; Sturmann, Laszlo; Sturmann, Judit; 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}}</ref> Sigma<sup>1</sup> is a yellow main sequence star of spectral type G1V and weighing around 1 ].<ref name="Raghavan 2009"/> Sigma<sup>2</sup> is a spectroscopic binary system composed of two stars very close (6 solar radii) together that orbit each other every 1.14 days.<ref name=kalersigma/> These stars are 1.14 and 1.09 times as massive as the Sun,<ref name="Raghavan 2009"/> with spectral types F9V and G0V respectively. They rotate each other very rapidly, and are very active as a result, with prominent star spots and are classed as ]s.<ref name=kalersigma/> The system emits radio waves.<ref name=Lestrade/> Much further away, at a distance of 14,000 astronomical units (AU), are a pair of red dwarf stars that take 52 years to rotate each other. This pair has an apparent magnitude of 12,24.<ref name="Raghavan 2009"/> |
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'''Sigma Coronae Borealis''' is a multiple star system in the constellation ], the main components of which are three sunlike stars.<ref name=kalersigma>{{cite web| first1=James B. | last1=Kaler | title=Sigma Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/sigmacrb.html | accessdate=23 November 2014}}</ref> Appearing as a single star of apparent magnitude 5.3 to the unaided eye, Sigma can be separated into 6.6-magnitude Sigma<sup>1</sup> and 5.64-magnitude Sigma<sup>2</sup> when observed with a telescope.<ref name=kalersigma/> The two take 726 years to orbit each other.<ref name="Raghavan 2009">{{cite journal|last=Raghavan, Deepak; McAlister, Harold A.; Torres, Guillermo; Latham, David W.; Mason, Brian D.; Boyajian, Tabetha S.; Baines, Ellyn K.; Williams, Stephen J.; ten Brummelaar, Theo A.; Farrington, Chris D.; Ridgway, Stephen T.; Sturmann, Laszlo; Sturmann, Judit; 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}}</ref> Sigma<sup>1</sup> is a yellow main sequence star of spectral type G1V and weighing around 1 ].<ref name="Raghavan 2009"/> Sigma<sup>2</sup> is a spectroscopic binary system composed of two stars very close (6 solar radii) together that orbit each other every 1.14 days.<ref name=kalersigma/> These stars are 1.14 and 1.09 times as massive as the Sun,<ref name="Raghavan 2009"/> with spectral types F9V and G0V respectively. They rotate each other very rapidly, and are very active as a result, with prominent star spots and are classed as ]s.<ref name=kalersigma/> The system emits radio waves.<ref name=Lestrade/> Much further away, at a distance of 14,000 astronomical units (AU), are a pair of red dwarf stars that take 52 years to rotate each other. This pair has an apparent magnitude of 12,24.<ref name="Raghavan 2009"/> |
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The system is thought to be anywhere from 100 million to 3 billion years old, from measurement of lithium in its spectrum.<ref name="Raghavan 2009"/> Its parallax was measured in 1999.<ref name=Lestrade/> |
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The system is thought to be anywhere from 100 million to 3 billion years old, from measurement of lithium in its spectrum.<ref name="Raghavan 2009"/> Its parallax was measured in 1999, yielding a distance of 74.2 light-years.<ref name=Lestrade/> |
