102 Herculis

102 Herculis
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 18h 08m 45.49142s[1]
Declination +20° 48′ 52.4079″[1]
Apparent magnitude (V) 4.37[2]
Characteristics
Spectral type B2 IV[3][4] or B2 V[5][6]
B−V color index −0.164±0.013[2]
Astrometry
Radial velocity (Rv)−14.9±0.6[2] km/s
Proper motion (μ) RA: −1.92[1] mas/yr
Dec.: −5.89[1] mas/yr
Parallax (π)3.56±0.19 mas[1]
Distance920 ± 50 ly
(280 ± 10 pc)
Absolute magnitude (MV)−2.87[2]
Details
Mass9.7±0.2[4] M☉
Luminosity3,631.92[2] L☉
Surface gravity (log g)3.54[7] cgs
Temperature22,420±1,440[8] K
Rotational velocity (v sin i)41[9] km/s
Age20.0±1.4[4] Myr
Other designations
Ramus, 102 Her, BD+20°3674, FK5 3443, HD 166182, HIP 88886, HR 6787, SAO 85769, WDS J18088+2049[10]
Database references
SIMBADdata

102 Herculis, also named Ramus,[11] is a single[12] star in the northern constellation of Hercules. It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 4.37.[2] Based upon parallax measurements, it is located around 920 light years away from the Sun.[1] The star is moving closer to the Earth with a heliocentric radial velocity of −15 km/s.[2]

The stellar classification of this object matches a massive, early B-type star with a luminosity class of IV[3] or V,[5] corresponding to a subgiant or main sequence star, respectively. It is 20[4] million years old with nearly ten[4] times the mass of the Sun and is spinning with a projected rotational velocity of 41 km/s.[9] The strength of the stellar magnetic field has been measured at (209.5±135.4)×10−4 T.[6] The star is radiating 3,632[2] times the Sun's luminosity from its photosphere at an effective temperature of 22,420 K.[8]

Etymology

In Chinese, 帛度 (Bó Dù), meaning Textile Ruler, refers to an asterism consisting of 102 Herculis and 95 Herculis.[13] Consequently, 102 Herculis itself is known as 帛度二 (Bó Dù èr, English: the Second Star of Textile Ruler.)

This star, together with 93 Herculis, 95 Herculis, and 109 Herculis, formed the now obsolete constellation of Cerberus, which was sometimes combined with Ramus, the apple branch.[14] The IAU Working Group on Star Names approved the name Ramus for this star on 17 June 2025 and it is now so entered in the IAU Catalog of Star Names.[11] The WGSN avoided using the name Cerberus since it was already in use for the asteroid 1865 Cerberus.[15]

References

  1. ^ a b c d e f van Leeuwen, F. (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. ^ a b c d e f g h 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. ^ a b Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
  4. ^ a b c d e Tetzlaff, N.; et al. (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.
  5. ^ a b Eggen, Olin J. (1961), "Space motions and distribution of the apparently bright B-type stars", Royal Observatory Bulletins, 41: 245–287, Bibcode:1961RGOB...41..245E.
  6. ^ a b Bychkov, V. D.; et al. (August 2003), "Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars", Astronomy and Astrophysics, 407 (2): 631–642, arXiv:astro-ph/0307356, Bibcode:2003A&A...407..631B, doi:10.1051/0004-6361:20030741, S2CID 14184105.
  7. ^ Lyubimkov, L. S.; et al. (June 2004), "Surface abundances of light elements for a large sample of early B-type stars - III. An analysis of helium lines in spectra of 102 stars", Monthly Notices of the Royal Astronomical Society, 351 (2): 745–767, Bibcode:2004MNRAS.351..745L, doi:10.1111/j.1365-2966.2004.07825.x.
  8. ^ a b Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147, S2CID 14969137.
  9. ^ a b Simón-Díaz, S.; et al. (2017), "The IACOB project . III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars", Astronomy and Astrophysics, 597: A22, arXiv:1608.05508, Bibcode:2017A&A...597A..22S, doi:10.1051/0004-6361/201628541, S2CID 3478126.
  10. ^ "102 Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-17.
  11. ^ a b "IAU Catalog of Star Names". Retrieved 17 June 2025.
  12. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  13. ^ "Bodu (帛度)". All Skies Encyclopaedia. IAU Working Group on Star Names. Retrieved 17 June 2025.
  14. ^ Ian Ridpath's Star Tales - Cerberus
  15. ^ "Ramus". All Skies Encyclopaedia. IAU Working Group on Star Names. Retrieved 17 June 2025.
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