Eta Coronae Borealis
 A star chart of the constellation of Coronae Borealis showing the position of Eta Coronae Borealis (circled) |
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| Observation data Epoch J2000.0 Equinox J2000.0 |
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|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 23m 12.31s[1] |
| Declination | +30° 17′ 16.17″[1] |
| Apparent magnitude (V) | 5.02 |
| Characteristics | |
| Spectral type | G1V[2] / G3V[2] / L8 [3] |
| B−V color index | 0.56 |
| Astrometry | |
| Radial velocity (Rv) | -7.410 ± 0.054[4] km/s |
| Proper motion (μ) | RA: 116.83 ± 0.40[1] mas/yr Dec.: -171.37 ± 0.49[1] mas/yr |
| Parallax (π) | 55.98 ± 0.78[1] mas |
| Distance | 58.3 ± 0.8 ly (17.9 ± 0.2 pc) |
| Orbit[4] | |
| Primary | Eta Coronae Borealis A |
| Companion | Eta Coronae Borealis B |
| Period (P) | 15189.1 ± 2.9 days |
| Semi-major axis (a) | 0.860 ± 0.003" |
| Eccentricity (e) | 0.277 ± 0.001 |
| Inclination (i) | 58.7 ± 0.16° |
| Longitude of the node (Ω) | 22.9 ± 0.19° |
| Periastron epoch (T) | 1892.317 ± 0.031 |
| Argument of periastron (ω) (secondary) |
39.24 ± 0.37° |
| Argument of periastron (ω) (primary) |
219.2 ± 0.37° |
| Semi-amplitude (K1) (primary) |
4.709 ± 0.095 km/s |
| Semi-amplitude (K2) (secondary) |
5.276 ± 0.054 km/s |
| Position (relative to Eta Coronae Borealis AB)[3] | |
| Component | Eta Coronae Borealis C |
| Angular distance | 194″ |
| Position angle | 136° |
| Observed separation (projected) |
~3600 AU |
| Details | |
| Mass | 1.19 ± 0.071[4] / 1.05 ± 0.05[4] / 0.060 ± 0.015[3] M☉ |
| Metallicity [Fe/H] | -0.20[5] dex |
| Age | 1-2.5[3] Gyr |
| Other designations | |
|
2 Coronae Borealis, HD 137107/137108, HIP 75312, Gliese 584, HR 5727
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| Database references | |
| SIMBAD | data |
Eta Coronae Borealis (η Coronae Borealis, η CrB) is a stellar system that lies approximately 58 light-years away. The primary component is a mid-wide binary, while a brown dwarf component is located at a wide separation.
Components
Eta Coronae Borealis has been known since the late 18th century to be a moderate-separation binary. The orbit of the two components takes approximately 42 years, which when combined with the distance to the system makes the two stars fairly easily resolvable with a larger telescope. The two stars have similar physical parameters, though the secondary is slightly cooler than the primary and has approximately 90% of the primary's mass. Possible stable planetary orbits in the habitable zone were calculated for the system in 1996.[6]
A brown dwarf companion was detected in 2001. The source 2MASSW J1523226+301456 in the 2MASS catalogue was identified as having a similar proper motion to the AB binary, and subsequent observations confirmed its relationship to the system. The new component, Eta Coronae Borealis C, was found to have a spectral type of L8. The brown dwarf has a minimum separation of 3600 AU, and considering a cooling age of 1–2.5 gigayears, the brown dwarf has a mass of 0.060 ± 0.015 M☉, or 63 ± 16 MJ.[3]
See also
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 4.2 4.3 4.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
