Tau Aquilae

Tau Aquilae
Location of τ Aquilae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Aquila
Right ascension 20h 04m 08.31506s[1]
Declination +07° 16′ 40.6705″[1]
Apparent magnitude (V) 5.6799±0.0009[2]
Characteristics
Spectral type K0 III[3]
U−B color index +0.86[4]
B−V color index +1.06[4]
Astrometry
Radial velocity (Rv)−29.27±0.13[1] km/s
Proper motion (μ) RA: +14.039[1] mas/yr
Dec.: +12.141[1] mas/yr
Parallax (π)5.9403 ± 0.0883 mas[1]
Distance549 ± 8 ly
(168 ± 3 pc)
Absolute magnitude (MV)−0.24[5]
Details
Radius21.24+0.84
−1.05[1] R☉
Luminosity207.9±3.8[1] L☉
Surface gravity (log g)2.69[3] cgs
Temperature4756+110
−92[1] K
Metallicity [Fe/H]–0.15[3] dex
Other designations
τ Aql, 63 Aquilae, BD+06 4416, FK5 1524, HD 190327, HIP 98823, HR 7669, SAO 125403[6]
Database references
SIMBADdata

Tau Aquilae, Latinized from τ Aquilae, is the Bayer designation for a star in the equatorial constellation of Aquila. The apparent visual magnitude of 5.7[2] indicates it is a faint star that is visible to the naked eye from suburban skies; at least according to the Bortle Dark-Sky Scale. The annual orbital motion of the Earth causes a parallax shift of 5.94 mas,[1] which means the distance to this star is approximately 549 light-years (168 parsecs). The magnitude of the star is diminished by 0.28 from extinction caused by interstellar gas and dust.[2] It is drifting closer to the Sun with a radial velocity of −29 km/s.[1]

The spectrum of Tau Aquilae matches a stellar classification of K0 III,[3] with the luminosity class of III suggesting this is an evolved giant star that has exhausted the supply of hydrogen at its core and left the main sequence of stars like the Sun. It has 21[1] times the girth of the Sun and is radiating 208 times the Sun's luminosity.[1] The outer envelope is radiating energy into space with an effective temperature of 4,660 K,[3] giving it the orange hued glow of a K-type star.[7]

References

  1. ^ a b c d e f g h i j k l m 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. Gaia DR2 record for this source at VizieR.
  2. ^ a b c Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
  3. ^ a b c d e McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
  4. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  5. ^ 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, S2CID 119257644.
  6. ^ "* tau Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-21.{{cite web}}: CS1 maint: postscript (link)
  7. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2021-02-20