Zeta Sagittarii

ζ Sagittarii
Location of ζ Sagittarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 19h 02m 36.73024s[1]
Declination –29° 52′ 48.2279″[1]
Apparent magnitude (V) +2.59[2] (3.27/3.48)[3]
Characteristics
Spectral type A2.5 Va[4]
U−B color index +0.05[2]
B−V color index +0.08[2]
Astrometry
Radial velocity (Rv)+22[5] km/s
Proper motion (μ) RA: +10.79[1] mas/yr
Dec.: +21.11[1] mas/yr
Parallax (π)36.98 ± 0.87 mas[1]
Distance88 ± 2 ly
(27.0 ± 0.6 pc)
Absolute magnitude (MV)1.11/1.32[3]
Orbit[6]
PrimaryAa
CompanionAb
Period (P)1 month
Semi-major axis (a)0.3 au
Orbit[3]
PrimaryA
CompanionB
Period (P)21.00 ± 0.01 years
Semi-major axis (a)0.489 ± 0.001"[3] (13.2 au)[6]
Eccentricity (e)0.211 ± 0.001
Inclination (i)111.1 ± 0.1°
Longitude of the node (Ω)74.0 ± 0.1°
Periastron epoch (T)2005.99 ± 0.03
Argument of periastron (ω)
(secondary)		7.2 ± 0.6°
Details[6]
Aa
Mass1.83 M☉
Radius1.9 R☉
Luminosity14.9[a] L☉
Surface gravity (log g)3.90[7] cgs
Temperature8,230 K
Rotational velocity (v sin i)77[8] km/s
Age700 Myr
Ab
Mass1.81 M☉
Radius1.9 R☉
Luminosity14.7[a] L☉
Temperature8,200 K
Age700 Myr
B
Mass2.03 M☉
Radius2.3 R☉
Luminosity24[a] L☉
Temperature8,460 K
Age700 Myr
Other designations
Ascella, ζ Sagittarii, ζ Sgr, Zeta Sgr, 38 Sagittarii, CCDM J19026-2953AB, CPD-30  5798, GC 26161, HD 176687, HIP 93506, HR 7194, IDS 18562-3001 AB, PPM 269230, SAO 187600, WDS J19026-2953AB
Database references
SIMBADdata

Zeta Sagittarii (ζ Sagittarii, abbreviated Zeta Sgr, ζ Sgr) is a triple star system and the third-brightest star in the constellation of Sagittarius after Kaus Australis and Nunki. Based upon parallax measurements, it is about 88 light-years (27 parsecs) from the Sun.[1]

The three components are designated Zeta Sagittarii Aa (officially named Ascella /əˈsɛlə/, the traditional name for the entire system),[9][10] Ab and B.[6] The Washington Double Star Catalog cites a component separated 72.3" from the system, but it is a background star unrelated to the pair.[6]

  1. ^ a b c d e f Cite error: The named reference hipparcos was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference clpl4 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference de_rosa_et_al_2011 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference gcsrv was invoked but never defined (see the help page).
  6. ^ a b c d e Cite error: The named reference waisberg was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference aj126_4_2048 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference rotvel was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Davis44 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference IAU-LSN was invoked but never defined (see the help page).


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