Omicron Coronae Borealis

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o Corona Borealis
Corona Borealis constellation map.svg
Red circle.svg
Location of o Corona Borealis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Corona Borealis
Right ascension 15h 20m 08.559s[1]
Declination +29° 36′ 58.35″[1]
Apparent magnitude (V) +5.53[2]
Spectral type K0 III[3]
U−B color index +0.786[2]
B−V color index +1.009[2]
Radial velocity (Rv) −54.15±0.20[4] km/s
Proper motion (μ) RA: −117.98±0.18[1] mas/yr
Dec.: −42.44±0.31[1] mas/yr
Parallax (π) 12.08 ± 0.44[1] mas
Distance 270 ± 10 ly
(83 ± 3 pc)
Absolute magnitude (MV) +0.92[3]
Mass 1.07±0.19 M
Radius 10.13±0.40 R
Luminosity 50.1 L
Surface gravity (log g) 2.70±0.06 cgs
Temperature 4,812±13 K
Metallicity [Fe/H] −0.24±0.01 dex
Rotational velocity (v sin i) 0.47±0.61 km/s
Age 5.54±2.79 Gyr
Other designations
o CrB, 1 Coronae Borealis, BD+30° 2647, HD 136512, HIP 75049, HR 5709, SAO 83768, WDS J15201+2937A
Database references
Exoplanet Archive data
Extrasolar Planets

Omicron Coronae Borealis, Latinized from o Coronae Borealis, is a star in the northern constellation of Corona Borealis. It is a faint star but visible to the naked eye on a dark night with an apparent visual magnitude of +5.53.[2] The annual parallax shift of the star as seen from Earth is 12.08 mas, which provides a distance estimate of around 270 light years. It is moving closer to the Sun with a radial velocity of −54 km/s.[4]

Based upon the spectrum of this star, it has a stellar classification of K0 III.[3] This indicates this is an evolved K-type giant star that has exhausted the hydrogen at its core and has left the main sequence. This is a red clump star, which means it is now generating energy through helium fusion at its core. It has 10% of the mass of the Sun and has expanded to over ten times the Sun's radius. The star is radiating 50 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,812 K.[5]

Omicron Coronae Borealis has one confirmed planet, believed to be, like HD 100655 b, one of the two least massive planets known around clump giants.[6] The planet was detected by measuring changes in radial velocity of the host star caused by gravitational perturbation of the orbiting object. It is orbiting with a period of 188 days, at a semimajor axis 83% of the mean separation between the Earth and the Sun, and an eccentricity of 0.19.[5]

The Omicron Coronae Borealis planetary system[5]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b >1.5 MJ 0.83 187.83 ± 0.54 0.191 ± 0.085


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c d Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172: 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667. 
  3. ^ a b c Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971Freely accessible, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. 
  4. ^ a b c Jofré, E; et al. (2015), "Stellar parameters and chemical abundances of 223 evolved stars with and without planets", Astronomy & Astrophysics, 574, Bibcode:2015A&A...574A..50J, doi:10.1051/0004-6361/201424474, A50. 
  5. ^ a b c Sato, Bun'ei; et al. (2012), "Substellar Companions to Seven Evolved Intermediate-Mass Stars", Publications of the Astronomical Society of Japan, 64 (6), 135, arXiv:1207.3141Freely accessible, Bibcode:2012PASJ...64..135S, doi:10.1093/pasj/64.6.135. 
  6. ^ Sato. Its m sin i is the least, but the true-mass depends on error and inclination.