Sigma Coronae Borealis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 16h 14m 40.85557s[1] |
| Declination | +33° 51′ 30.9497″[1] |
| Apparent magnitude (V) | 5.64[1] |
| Astrometry | |
| Radial velocity (Rv) | -12.30 km/s |
| Proper motion (μ) | RA: -263.39 mas/yr Dec.: -92.67 mas/yr |
| Parallax (π) | 43.93 ± 0.10[2] mas |
| Distance | 74.2 ± 0.2 ly (22.76 ± 0.05 pc) |
| Other designations | |
Sigma Coronae Borealis is a quintuple star system in the constellation Corona Borealis, the main components of which are three sunlike stars.[3] Appearing as a single star of apparent magnitude 5.3 to the unaided eye, Sigma can be separated into 6.6-magnitude Sigma1 and 5.64-magnitude Sigma2 when observed with a telescope.[3] The two take 726 years to orbit each other.[4] The orbit of Sigma1 is eccentric, with an average distance of 128 AU, and a minimum of 31 AU and maximum of 225 AU.[3] Sigma1 is a yellow main sequence star of spectral type G1V and weighing around 1 solar mass.[4] Sigma2 is a spectroscopic binary system composed of two stars very close (6 solar radii) together that orbit each other every 1.14 days.[3] These stars are 1.14 and 1.09 times as massive as the Sun,[4] with spectral types F9V and G0V respectively.[3] Each has a diameter around 1.2 times that of the Sun.[4] They rotate each other very rapidly, and are very active as a result, with prominent star spots and are classed as RS Canum Venaticorum variables.[3] The system emits radio waves.[2] 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.[4] This pair has a combined apparent magnitude of 12.24.[4] Another pair of faint stars that appear nearby were found to be unrelated.[4]
The system is thought to be anywhere from 100 million to 3 billion years old, from measurement of lithium in its spectrum.[4] Its parallax was measured in 1999, yielding a distance of 74.2 light-years.[2]
References
- 1 2 3 "Sigma Coronae Borealis - Variable of RS CVn type". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 23 November 2014.
- 1 2 3 Lestrade, J.-F.; Preston, R. A.; Jones, D. L.; Phillips, R. B.; et al. (1999). "High-precision VLBI astrometry of radio-emitting stars". Astronomy and Astrophysics. 344: 1014–26. Bibcode:1999A&A...344.1014L.
- 1 2 3 4 5 6 Kaler, James B. "Sigma Coronae Borealis". Stars. University of Illinois. Retrieved 23 November 2014.
- 1 2 3 4 5 6 7 8 Raghavan, Deepak; McAlister, Harold A.; Torres, Guillermo; Latham, David W.; et al. (2009). "The Visual Orbit of the 1.1 Day Spectroscopic Binary σ2 Coronae Borealis from Interferometry at the Chara Array". The Astrophysical Journal. 690 (1): 394–406. arXiv:0808.4015
. Bibcode:2009ApJ...690..394R. doi:10.1088/0004-637X/690/1/394.