Eta Horologii

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Eta Horologii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Horologium
Right ascension 02h 37m 24.37297s[1]
Declination −52° 32′ 35.0855″[1]
Apparent magnitude (V) 5.31[2]
Spectral type A6 V + F0 V[3]
B−V color index +0.27[2]
Radial velocity (Rv) −3.0±7.4[4] km/s
Proper motion (μ) RA: +112.70[1] mas/yr
Dec.: +3.73[1] mas/yr
Parallax (π) 21.95 ± 1.10[1] mas
Distance 149 ± 7 ly
(46 ± 2 pc)
Absolute magnitude (MV) 2.13[5]
Period (P) 3.01±0.18 yr
Semi-major axis (a) 0.0231±0.0014
Eccentricity (e) 0.16±0.14
η Hor A
Mass 1.56[7] M
Luminosity 12.6[8] L
Surface gravity (log g) 4.21[7] cgs
Temperature 7,552±257[7] K
Rotational velocity (v sin i) 6.6±2.2[5] km/s
Age 474[7] Myr
Other designations
η Hor, CPD−53° 457, FK5 2182, HD 16555, HIP 12225, HR 778, SAO 232835[9]
Database references

Eta Horologii (η Horologii, η Hor) is an astrometric binary[3] star system in the southern constellation of Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 5.31.[2] Based upon an annual parallax shift of 21.95 mas as seen from Earth,[1] it is located around 149 light years from the Sun.

The orbit for this pair is not yet well constrained. They appear to have an orbital period of three years and an eccentricity of roughly 0.16.[6] As of 2012, the pair have an angular separation of 78.7 mas, which corresponds to a projected separation of 3.6 AU.[3] The primary member, component A, is an A-type main sequence star with a stellar classification of A6 V. The secondary, component B, has an inferred class of F0 V, which would indicate it is an F-type main sequence star.[3]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  3. ^ a b c d Marion, L.; et al. (October 2014), "Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey", Astronomy & Astrophysics, 570: 12, Bibcode:2014A&A...570A.127M, doi:10.1051/0004-6361/201424780, A127. 
  4. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, Bibcode:2012A&A...546A..61D, arXiv:1208.3048Freely accessible, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ a b Ammler-von Eiff, M.; Reiners, A. (2012), "New measurements of rotation and differential rotation in A-F stars: Are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724. 
  6. ^ a b Malkov, O. Yu.; et al. (2012), "Dynamical Masses of a Selected Sample of Orbital Binaries", Astronomy & Astrophysics, 546: 5, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774, A69. 
  7. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, Bibcode:2015ApJ...804..146D, arXiv:1501.03154Freely accessible, doi:10.1088/0004-637X/804/2/146. 
  8. ^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037Freely accessible, doi:10.1111/j.1365-2966.2012.21873.x 
  9. ^ "eta Hor -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-04-25.