Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Corona Borealis |
Right ascension | 15h 57m 35.25147s[1] |
Declination | +26° 52′ 40.3635″[1] |
Apparent magnitude (V) | 4.13[2] |
Characteristics | |
Spectral type | K2 III[2] |
U−B color index | +1.28[3] |
B−V color index | +1.235[3] |
Astrometry | |
Radial velocity (Rv) | –32.42[2] km/s |
Proper motion (μ) | RA: –77.07[1] mas/yr Dec.: –60.61[1] mas/yr |
Parallax (π) | 13.4922 ± 0.1023 mas[4] |
Distance | 242 ± 2 ly (74.1 ± 0.6 pc) |
Absolute magnitude (MV) | −0.02[5] |
Details | |
Mass | 1.44±0.18[6] M☉ |
Radius | 21[7] R☉ |
Luminosity (bolometric) | 151[2] L☉ |
Surface gravity (log g) | 1.94±0.15[6] cgs |
Temperature | 4,365±28[2] K |
Metallicity [Fe/H] | −0.22±0.03[6] dex |
Rotational velocity (v sin i) | 2.4[7] km/s |
Age | 4.13[2] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the constellation Corona Borealis located around 230 light-years from the Solar System. It shines with a combined apparent magnitude of 4.13,[8] meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations.[9] It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III,[10] which has exhausted its core fuel supply of hydrogen and swollen to 21 times the Sun's diameter and 151 times its luminosity.[7] That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit.[11] Its surface temperature has been calculated to be 4365 ± 9 K,[7] or 4406 ± 15 K.[10] It is thought to be around 1.74 billion years old.[10]
Epsilon Coronae Borealis B is a companion star thought to be an orange dwarf of spectral types K3V to K9V that orbits at a distance of 135 astronomical units, completing one orbit every 900 years.[11]
A faint (magnitude 11.5) star, 1.5 arc minutes away, has been called Epsilon Coronae Borealis C although it is only close by line of sight and is unrelated to the system.[11][12]
Epsilon Coronae Borealis lies one degree north of (and is used as a guide for) the variable T Coronae Borealis.[11]
The ε CrB star system's radial velocity was observed over seven years from January 2005 to January 2012, during which time a 'wobble' with a period of around 418 days was recorded. This has been calculated to be a planet around 6.7 times as massive as Jupiter orbiting at a distance of 1.3 astronomical units with an eccentricity of 0.11.[10]
Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | ≥6.7 ± 0.3 MJ | 1.3 | 417.9 ± 0.5 | 0.11 ± 0.03 | — | — |