Eta Ophiuchi

Eta Ophiuchi (Sabik)
Location of η Ophiuchi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 17h 10m 22.68689s[1]
Declination –15° 43′ 29.6639″[1]
Apparent magnitude (V) 2.43[2] (3.05/3.27)[3]
Characteristics
Spectral type A1 IV + A1 IV[3]
U−B color index +0.09[2]
B−V color index +0.05[2]
Astrometry
Radial velocity (Rv)–0.9[4] km/s
Proper motion (μ) RA: +40.13[1] mas/yr
Dec.: +99.17[1] mas/yr
Parallax (π)36.91 ± 0.80 mas[1]
Distance88 ± 2 ly
(27.1 ± 0.6 pc)
Orbit[3]
Period (P)87.58 ± 1.00 yr
Semi-major axis (a)1.396 ± 0.010″
Eccentricity (e)0.950 ± 0.020
Inclination (i)95.2 ± 2.0°
Longitude of the node (Ω)38.9 ± 1.0°
Periastron epoch (T)2024.68 ± 0.50
Argument of periastron (ω)
(secondary)		274.8 ± 2.0°
η Oph A
Mass2.966[3] M☉
Radius2.5[5] R☉
Luminosity35[5] L☉
Surface gravity (log g)3.74[6] cgs
Temperature8,900[5] K
Metallicity−0.01[6] dex
Rotational velocity (v sin i)23[7] km/s
η Oph B
Mass3.478[3] M☉
Radius2[5] R☉
Luminosity21[5] L☉
Temperature8,600[5] K
Other designations
35 Oph, BD–15°4467, GCTP 3895.00, Gl 656.1A/B, HD 155125, HIP 84012, HR 6378, SAO 160332, WDS J17104-1544AB.
Database references
SIMBADdata

Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. Based on parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years from the Sun.

Eta Ophiuchi is part of a multiple star system designated WDS J17104-1544. It itself is designated WDS J17104-1544AB and its two components WDS J17104-1544A (also called Sabik /ˈseɪbɪk/, the traditional name for the system)[8][9] and WDS J17104-1544B. The 'C' component is UCAC4 372-080717[10] and 'D' is UCAC2 26022336.[11]

  1. ^ a b c d e Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c Hoffleit, D.; Warren, W. H. Jr. (1991). "Entry for HR 2491". Bright Star Catalogue (5th revised (Preliminary Version) ed.). CDS. ID V/50.
  3. ^ a b c d e Cite error: The named reference aj133_4_1209 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference gcsrv was invoked but never defined (see the help page).
  5. ^ a b c d e f Sabik. stars.astro.illinois.edu. Retrieved July 1, 2024.
  6. ^ a b Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  7. ^ Cite error: The named reference aaa463_2_671 was invoked but never defined (see the help page).
  8. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  9. ^ "Naming Stars". IAU.org. Retrieved 27 February 2018.
  10. ^ "UCAC4 372-080717 -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2018-02-27
  11. ^ "UCAC2 26022336 -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2018-02-27