HD 129116

HD 129116 is a binary star[10] in the northeastern part of Centaurus, east of Menkent. It is also known by its Bayer designation of b Centauri, while HD 129116 is the star's identifier in the Henry Draper catalogue. This object has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.01.[2] It is located at a distance of approximately 325 light years[11][5] from the Sun based on parallax, and has an absolute magnitude of −1.07.[2] The star is a probable (93% chance) member of the Sco OB2 moving group of stars.[12]

b Centauri

b Centauri imaged by VLT/SPHERE. The planet b Centauri b is indicated by an arrow.
Credit: ESO/Janson et al.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 14h 41m 57.59068s[1]
Declination −37° 47′ 36.5940″[1]
Apparent magnitude (V) +4.01[2]
Characteristics
Evolutionary stage Main sequence
Spectral type B3V[3]
B−V color index −0.157±0.002[2]
Variable type Constant[4]
Astrometry
Radial velocity (Rv)+2.6±1.5[2] km/s
Proper motion (μ) RA: −29.828±0.369[5] mas/yr
Dec.: −31.914±0.518[5] mas/yr
Parallax (π)10.0339 ± 0.3143[5] mas
Distance323.37±7.93 ly
(99.193±2.432 pc)
Absolute magnitude (MV)−1.07[2]
Details
Mass6.3±0.1[6] M☉
Radius2.93±0.12[7] R☉
Luminosity637.01[2] L☉
Surface gravity (log g)4.23±0.03[7] cgs
Temperature18,445±344[7] K
Rotational velocity (v sin i)129[8] km/s
Age18.4±1.5[6] Myr
Other designations
b Cen, CD−37°9618, FK5 2985, GC 19779, HD 129116, HIP 71865, HR 5471, SAO 205839[9]
Database references
SIMBADdata
This article is about b Centauri. Not to be confused with Alpha Centauri B. For B Centauri, see B Centauri. For β Centauri, see Beta Centauri.

This is a B-type main-sequence star with a stellar classification of B3V,[3] which indicates it is engaged in core hydrogen fusion to generate energy. The object has been used as a "standard star" in several photometric systems, and it appears to be non-variable.[4] It is an estimated 18[6] million years old with a high rate of spin, showing a projected rotational velocity of 129 km/s.[8] The star has 6.3[6] times the mass of the Sun and 2.9[7] times the Sun's radius. It is radiating 637[2] times the luminosity of the Sun from its photosphere at an effective temperature of 18,445 K.[7]

Planetary system
Artist's impression showing b Centauri and its giant planet b Centauri b.

In 2021, an exoplanet with a mass of 10.9 MJ was directly imaged in orbit around b Centauri by VLT/SPHERE.[10]

The b Centauri planetary system[10]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(years)		 Eccentricity Inclination Radius
b 10.9±1.6 MJ 556±17 2650–7170 <0.40 128–157° —

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  3. Hiltner, W. A.; et al. (July 1969), "MK Spectral Types for Bright Southern OB Stars", Astrophysical Journal, 157: 313–326, Bibcode:1969ApJ...157..313H, doi:10.1086/150069.
  4. Paunzen, E.; Rode-Paunzen, M. (2017). "BRITE photometry of seven B-type stars". Second Brite-Constellation Science Conference: Small Satellites – Big Science. 5: 180. arXiv:1612.04714. Bibcode:2017sbcs.conf..180P.
  5. European Space Agency. "Gaia EDR3". doi:10.5270/esa-1ugzkg7. Cite journal requires |journal= (help)
  6. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  7. Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal, 129 (3): 1642–1662, arXiv:astro-ph/0412542, Bibcode:2005AJ....129.1642F, doi:10.1086/427855, S2CID 119512018.
  8. Wolff, S. C.; Strom, S. E.; Dror, D.; Venn, K. (2007), "Rotational Velocities for B0-B3 Stars in Seven Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions", The Astronomical Journal, 133 (3): 1092–1103, arXiv:astro-ph/0702133, Bibcode:2007AJ....133.1092W, doi:10.1086/511002, S2CID 119074863.
  9. "b Cen". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-05.
  10. "ESO telescope images planet around most massive star pair to date". European Southern Observatory. 8 December 2021. Retrieved 8 December 2021. See also attached research paper.
  11. Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating Distances from Parallaxes. V. Geometric and Photogeometric Distances to 1.47 Billion Stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. doi:10.3847/1538-3881/abd806. ISSN 0004-6256.CS1 maint: date and year (link)
  12. Rizzuto, Aaron; et al. (October 2011), "Multidimensional Bayesian membership analysis of the Sco OB2 moving group", Monthly Notices of the Royal Astronomical Society, 416 (4): 3108–3117, arXiv:1106.2857, Bibcode:2011MNRAS.416.3108R, doi:10.1111/j.1365-2966.2011.19256.x, S2CID 54510608.
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