31 Aquilae

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31 Aquilae
Diagram showing star positions and boundaries of the Aquila constellation and its surroundings
Cercle rouge 100%.svg
Location of 31 Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension  19h 24m 58.20027s[1]
Declination +11° 56′ 39.8862″[1]
Apparent magnitude (V) 5.16[2]
Spectral type G8 IV[2]
U−B color index +0.42[3]
B−V color index +0.77[2]
Radial velocity (Rv)–100.5[4] km/s
Proper motion (μ) RA: +721.02[1] mas/yr
Dec.: +642.49[1] mas/yr
Parallax (π)65.89 ± 0.26[1] mas
Distance49.5 ± 0.2 ly
(15.18 ± 0.06 pc)
Absolute bolometric
Mass1.16 ± 0.07[5] M
Radius1.379 ± 0.042[6] R
Luminosity1.904 ± 0.045[6] L
Surface gravity (log g)4.18 ± 0.03[5] cgs
Temperature5,510 ± 90[2] K
Metallicity [Fe/H]+0.37[7] dex
Age4.5 ± 0.2[5] Gyr
Other designations
BD+11 3833, FK5 1503, HD 182572, GJ 759, NLTT 47763, HIP 95447, HR 7373, LFT 1477, LHS 3463, LTT 15668, NSV 11994, SAO 104807.[8]
Database references

31 Aquilae (abbreviated 31 Aql) is a star in the equatorial constellation of Aquila. 31 Aquilae is its Flamsteed designation though it also bears the Bayer designation b Aquilae. This star has an apparent visual magnitude of 5.16 and is 49.5 light years from Earth. It has no known companions.


31 Aquilae has an apparent visual magnitude of 5.16,[2] making it bright enough to be seen with the naked eye in dark skies. The annual parallax shift of 65.89 mas[1] yields a distance estimate of 49.5 light-years (15.2 parsecs) from Earth. It is a variable star with a magnitude change of less than 0.02.[5]

With a stellar classification of G8 IV,[2] the luminosity class of IV indicates this is a subgiant star. Compared to the Sun, it has 116%[5] of the mass and 138%[6] of the radius. It is radiating nearly double[6] the luminosity of the Sun from its outer atmosphere at an effective temperature of 5,510 K,[2] giving it the yellow hue of a G-type star.[9] Its age is probably similar to NGC 188, the oldest open cluster known, which was calculated to be over 5 billion years. For its age, it is surprisingly rich in elements other than hydrogen or helium, contrary to common assumptions that the oldest stars should be metal-poor.

No certain substellar companion has been detected so far around 31 Aquilae. McDonald Observatory team has set limits to the presence of one or more planets [10] around 31 Aquilae with masses between 0.22 and 1.9 Jupiter masses and average separations spanning between 0.05 and 5.2 Astronomical Units.

Optical companions[edit]

The following stars are optical companions that are coincidentally aligned near the line of sight to 31 Aquilae.

Companion HD 231345 BD+11 3833C
Right ascension  19h 24m 51.8595s  19h 24m 50.8s
Declination +11° 57′ 14.692″ +11° 57′ 36″
Magnitude 8.56 10.6
Spectral type G0
Reference Simbad Simbad


  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 e f g Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M.
  3. ^ Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  4. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W.
  5. ^ a b c d e f Trevisan, M.; et al. (November 2011), "Analysis of old very metal rich stars in the solar neighbourhood", Astronomy & Astrophysics, 535: A42, arXiv:1109.6304, Bibcode:2011A&A...535A..42T, doi:10.1051/0004-6361/201016056. See Table 13.
  6. ^ a b c d Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101. See Table 10.
  7. ^ Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788.
  8. ^ "* b Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-22.
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16
  10. ^ Detection Limits from the McDonald Observatory Planet Search Program

External links[edit]