101 Aquarii

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101 Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Cercle rouge 100%.svg

Location of 101 Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 23h 33m 16.62300s[1]
Declination –20° 54′ 52.2155″[1]
Apparent magnitude (V) 4.71[2]
Spectral type A0 V[3]
U−B color index +0.00[2]
B−V color index +0.02[2]
Radial velocity (Rv) +15[4] km/s
Proper motion (μ) RA: –3.41[1] mas/yr
Dec.: +8.46[1] mas/yr
Parallax (π) 11.11 ± 0.67 mas
Distance 290 ± 20 ly
(90 ± 5 pc)
Rotational velocity (v sin i) 180[5] km/s
Other designations
b3 Aquarii, BD–21 6437, HD 221565, HIP 116247, HR 8939, SAO 191988.[6]
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

101 Aquarii or b3 Aquarii (101 Aqr) is the Flamsteed designation for a binary star[7] in the equatorial constellation of Aquarius. The combined apparent visual magnitude of the pair is 4.71,[2] which is bright enough to be seen with the naked eye from the suburbs. The distance of this star from Earth is estimated as 290 light-years (89 parsecs) based upon parallax measurements.[1]

The brighter member of this system has an apparent magnitude of 4.81. It is an A-type main sequence star with a stellar classification of A0 V.[3] This star is spinning rapidly with a projected rotational velocity of 1 km/s.[5] The fainter companion is a magnitude 7.43 star at an angular separation of 0.840 arcseconds.[7]


  1. ^ a b c d e 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. 
  2. ^ a b c d Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series 34: 1–49, Bibcode:1978A&AS...34....1N. 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H. 
  4. ^ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953QB901.W495...... 
  5. ^ a b Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224. 
  6. ^ "101 Aqr -- Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-03. 
  7. ^ a b 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. 

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