Epsilon Coronae Borealis
Epoch J2000 Equinox
|Right ascension||15h 57m 35.25147s |
|Declination||+26° 52′ 40.3635″ |
|Apparent magnitude (V)||4.13|
|Spectral type||K2III |
|Radial velocity (Rv)||–30.92 km/s|
|Proper motion (μ)||RA: -77.07 mas/yr
Dec.: -60.61 mas/yr
|Parallax (π)||13.97 ± 0.68 mas|
|Distance||230 ± 10 ly
(72 ± 3 pc)
|Luminosity (bolometric)||151 L☉|
|Temperature||4406 ± 15 K|
|Metallicity [Fe/H]||–0.094 ± 0.001 dex|
HD 143107, HR 5947, HIP 78159
Epsilon Coronae Borealis (ε CrB) 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, meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations. It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III, which has exhausted its core fuel supply of hydrogen and swollen to 21 times the Sun's diameter and 151 times its luminosity. That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit. Its surface temperature has been calculated to be 4365 ± 9 K, or 4406 ± 15 K. It is thought to be around 1.74 billion years old.
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.
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.
- SIMBAD, Epsilon Coronae Borealis (accessed 9 September 2012)
- Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 2013-02-20.
- Lee, B.-C.; Han, I.; Park, M.-G.; Mkrtichian, D. E.; Kim, K.-M. (2012). "A planetary companion around the K giant ɛ Corona Borealis". Astronomy & Astrophysics 546: 5. arXiv:1209.1187. Bibcode:2012A&A...546A...5L. doi:10.1051/0004-6361/201219347. A5.
- Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (January 2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal 135 (1): 209–31. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
- Kaler, James B. (19 August 2011). "Epsilon and T Coronae Borealis". Stars. University of Illinois. Retrieved 16 November 2014.
- SIMBAD, CCDM J15576+2652C -- Star in double system (accessed 16 November 2014)