17 Aquarii

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17 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  21h 22m 56.25866s[1]
Declination −09° 19′ 09.5823″[1]
Apparent magnitude (V) 5.99[2]
Spectral type K4/5 III[3]
B−V color index 1.516±0.008[2]
Radial velocity (Rv)18.2±2.9[4] km/s
Proper motion (μ) RA: −29.659[1] mas/yr
Dec.: −29.022[1] mas/yr
Parallax (π)4.9125 ± 0.1260[1] mas
Distance660 ± 20 ly
(204 ± 5 pc)
Absolute magnitude (MV)−0.73[2]
Period (P)7,290 d
Eccentricity (e)0.4
17 Aqr A
Luminosity495.46[2] L
Surface gravity (log g)1.74±0.14[6] cgs
Temperature3,951±14[6] K
Metallicity [Fe/H]−0.10±0.06[6] dex
Other designations
BD−09° 5728, FK5 3705, HD 203525, HIP 105574, HR 8175, SAO 145351[7]
Database references

17 Aquarii, abbreviated 17 Aqr, is a spectroscopic binary[5] star system in the constellation of Aquarius. 17 Aquarii is the Flamsteed designation. It appears to the naked eye as a faint sixth magnitude star, having a combined apparent visual magnitude of 5.99.[2] The distance to 17 Aqr can be estimated from its annual parallax shift of 4.9 mas,[1] which yields a separation of around 660 light years. It is moving further away with a heliocentric radial velocity of 18 km/s.[4]

A preliminary orbit for the pair gives a period of 20 years and an eccentricity of 0.4.[5] The primary component is an aging giant star with a stellar classification of K4/5 III,[3] it is radiating 495[2] times the Sun's luminosity from its photosphere at an effective temperature of 3,951 K.[6]


  1. ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. ^ a b c d e f 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.
  3. ^ a b Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
  4. ^ a b Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  5. ^ a b c Famaey, B.; et al. (2009). "Spectroscopic binaries among Hipparcos M giants,. I. Data, orbits, and intrinsic variations". Astronomy and Astrophysics. 498 (2): 627–640. arXiv:0901.0934. Bibcode:2009A&A...498..627F. doi:10.1051/0004-6361/200810698.
  6. ^ a b c d Wu, Yue; et al. (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014.
  7. ^ "17 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 22, 2018.