91 Aquarii

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For other stars named Psi Aqr, see Psi Aquarii

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

Location of ψ1 Aquarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Aquarius
Right ascension 23h 15m 53.49482s[1]
Declination –9° 05′ 15.8546″[1]
Apparent magnitude (V) +4.248[2]
Spectral type K0 III[3]
U−B color index +1.035[2]
B−V color index +1.104[2]
R−I color index 0.56[4]
Radial velocity (Rv) 25.49±0.74[5] km/s
Proper motion (μ) RA: +368.78[1] mas/yr
Dec.: –17.16[1] mas/yr
Parallax (π) 21.77 ± 0.29[1] mas
Distance 150 ± 2 ly
(45.9 ± 0.6 pc)
Mass 1.74±0.35[6] M
Radius 10.16±0.45[6] R
Luminosity 49[5] L
Surface gravity (log g) 2.6[5] cgs
Temperature 4603[5] K
Metallicity [Fe/H] –0.14[5] dex
Rotational velocity (v sin i) 2.9[5] km/s
Age 1.25+0.16
[7] Gyr
Other designations
Psi1 Aquarii, ADS 16633, BD–09 6156, FK5 1608, Gl 893.2, HD 219449, HIP 114855, HR 8841, LTT 9437, SAO 146598.
Database references
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)
Database references

91 Aquarii, also known as Psi1 Aquarii1 Aqr, ψ1 Aquarii), is the Flamsteed designation for a triple star[8] system in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of +4.248.[2] Parallax measurements yield an estimated distance of around 150 light-years (46 parsecs) from Earth.[1] An extrasolar planet is known to orbit the main star.

Stellar system[edit]

91 Aquarii is a triple star system.[8] The primary component, 91 Aqr A, is a giant star with a stellar classification of K0 III.[3] This is an evolved star with 174% of the Sun's mass that has expanded to over 10 times the size of the Sun.[6] It is radiating 49[5] times the Sun's luminosity from its outer envelope at an effective temperature of 4,603 K.[5] This gives it the orange-hued glow of a K-type star.[9]

The primary shares a common proper motion with two others stars, 91 Aqr B and C, suggesting that they are physically connected.[10] The latter pair form a binary system located at an angular separation of 52 arcseconds from the primary.[3] They are 10th magnitude stars separated by 0.3 arcseconds from each other.

Component Apparent

A 4.22 K0 III
B 9.62 K3 V
C 10.10

Because it lies near the same line of sight, the binary star system CCDM J23159-0905DE was listed to belong to the 91 Aquarii system according to the CCDM catalogue. However, it is listed as physically unconnected in the WDS catalogue and the pair have a different proper motion than 91 Aquarii.[10] CCDM J23159-0905DE has two components, the 13th magnitude CCDM J23159-0905D 80.4 arcseconds from 91 Aquarii, and the 14th magnitude CCDM J23159-0905E 19.7 arcseconds from 91 Aquarii.

Planetary system[edit]

In 2003, the discovery of an extrasolar planet orbiting 91 Aquarii A was announced. Despite controversy, the exoplanet was confirmed again on Jan 03, 2011 by the Conference " Planetary Systems Beyond the Main Sequence", Bamberg 2010 (Quirrenbach et al.).[citation needed]

The 91 Aquarii planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b ≥ 2.9[11] MJ ≥ 0.3[11] 182[12] 0

See also[edit]


  1. ^ a b c d e f 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 Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.", Monthly Notices of the Royal Astronomical Society 172: 667–679, Bibcode:1975MNRAS.172..667J. 
  3. ^ a b c Buscombe, W. (1962), "Spectral classification of Southern fundamental stars", Mount Stromlo Observatory Mimeogram 4, Bibcode:1962MtSOM...4....1B. 
  4. ^ VizieR Detailed Page for HR 8841, retrieved 2009-11-28. 
  5. ^ a b c d e f g h Massarotti, Alessandro et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209. 
  6. ^ a b c Ghezzi, L. et al. (December 2010), "Metallicities of Planet-hosting Stars: A Sample of Giants and Subgiants", The Astrophysical Journal 725 (1): 721–733, arXiv:1008.3539, Bibcode:2010ApJ...725..721G, doi:10.1088/0004-637X/725/1/721. 
  7. ^ Chanamé, Julio; Ramírez, Iván (February 2012), "Toward Precise Ages for Single Stars in the Field. Gyrochronology Constraints at Several Gyr Using Wide Binaries. I. Ages for Initial Sample", The Astrophysical Journal 746 (1): 102, arXiv:1109.0013, Bibcode:2012ApJ...746..102C, doi:10.1088/0004-637X/746/1/102 
  8. ^ 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. 
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16. 
  10. ^ a b Roell, T.; Neuhäuser, R.; Seifahrt, A.; Mugrauer, M. (June 2012), "Extrasolar planets in stellar multiple systems", Astronomy & Astrophysics 542: A92, arXiv:1204.4833, Bibcode:2012A&A...542A..92R, doi:10.1051/0004-6361/201118051 
  11. ^ a b Raghavan, Deepak et al. (July 2006), "Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems", The Astrophysical Journal 646 (1): 523–542, arXiv:astro-ph/0603836, Bibcode:2006ApJ...646..523R, doi:10.1086/504823. 
  12. ^ Mitchell, D. S.; S. Frink; A. Quirrenbach; D. A. Fischer; G. W. Marcy; R. P. Butler (2004-01-05). "Four Substellar Companions Found Around K Giant Stars". Bulletin of the American Astronomical Society, 35#5; AAS 203rd Meeting; Session 17 Extra Solar Planets. Retrieved 2009-11-28. 

External links[edit]

Coordinates: Sky map 23h 15m 53.5s, −09° 05′ 16″