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'''Sigma Coronae Borealis''' is a quintuple 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|display-authors=4|author=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}}</ref> The orbit of Sigma<sup>1</sup> is eccentric, with an average distance of 128 AU, and a minimum of 31 AU and maximum of 225 AU.<ref name=kalersigma/> 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.<ref name=kalersigma/> Each has a diameter around 1.2 times that of the Sun.<ref name="Raghavan 2009"/> 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.<ref name="Raghavan 2009"/> This pair has a combined apparent magnitude of 12.24.<ref name="Raghavan 2009"/> Another pair of faint stars that appear nearby were found to be unrelated.<ref name="Raghavan 2009"/> |
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'''Sigma Coronae Borealis''' is a quintuple 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|display-authors=4|author=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 }}</ref> The orbit of Sigma<sup>1</sup> is eccentric, with an average distance of 128 AU, and a minimum of 31 AU and maximum of 225 AU.<ref name=kalersigma/> 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.<ref name=kalersigma/> Each has a diameter around 1.2 times that of the Sun.<ref name="Raghavan 2009"/> 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.<ref name="Raghavan 2009"/> This pair has a combined apparent magnitude of 12.24.<ref name="Raghavan 2009"/> Another pair of faint stars that appear nearby were found to be unrelated.<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, yielding a distance of 74.2 light-years.<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/> |