Tau² Aquarii

τ² Aquarii
	Location of τ1 Aquarii (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Aquarius
Right ascension	22h 49m 35.50157s
Declination	–13° 35′ 33.4767″
Apparent magnitude (V)	+4.042
Characteristics
Spectral type	K5 III
U−B color index	+1.948
B−V color index	+1.566
Astrometry
Radial velocity (Rv)	+1.0 km/s
Proper motion (μ)	RA: –13.71 mas/yr ; Dec.: –39.03 mas/yr
Parallax (π)	10.27 ± 0.29 mas
Distance	318 ± 9 ly ; (97 ± 3 pc)
Details
Radius	53 R☉
Other designations
	Tau Aquarii, 71 Aquarii, BD–14 6354, FK5 861, HD 216032, HIP 112716, HR 8679, NSV 14329, SAO 165321.

For other star systems with this Bayer designation, see Tau Aquarii.

Tau² Aquarii (τ² Aqr, τ² Aquarii) is the Bayer designation for a star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of +4.0.^[2] This is an orange-hued^[7] giant star with a stellar classification of K5 III.^[3] The measured angular diameter, after correction for limb darkening, is 5.12 ± 0.05 mas.^[8] At an estimated distance of 318 light-years (97 parsecs) based on parallax measurements,^[1] this yields a physical size of about 53 times the radius of the Sun.^[5]

References

^ ^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.
^ ^a ^b ^c ^d Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, vol. 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G.
^ ^a ^b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions, Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W.
^ ^a ^b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(97\cdot 5.12\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 107\cdot R_{\bigodot }\end{aligned}}$
^ "tau Aqr -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-08
^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16
^ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039

External links

Image τ² Aquarii

[aaa474_2_653-1] ^ ^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.

[sps1966-2] Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, vol. 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G.

[houk1978-3] Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.

[scfs-4] Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions, Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W.

[lang2006-5] Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(97\cdot 5.12\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 107\cdot R_{\bigodot }\end{aligned}}$

[SIMBAD-6] "tau Aqr -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-08

[csiro-7] "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16

[aaa431_773-8] Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039

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Observation data Epoch J2000 Equinox J2000
Location of τ¹ Aquarii (circled)
Constellation	Aquarius
Right ascension	22^h 49^m 35.50157^s^[1]
Declination	–13° 35′ 33.4767″^[1]
Apparent magnitude (V)	+4.042^[2]
Characteristics
Spectral type	K5 III^[3]
U−B color index	+1.948^[2]
B−V color index	+1.566^[2]
Astrometry

Radial velocity (R_v)	+1.0^[4] km/s
Proper motion (μ)	RA: –13.71^[1] mas/yr Dec.: –39.03^[1] mas/yr
Parallax (π)	10.27 ± 0.29 mas^[1]
Distance	318 ± 9 ly (97 ± 3 pc)

Details

Radius	53^[5] `R`_☉

Other designations
Tau Aquarii, 71 Aquarii, BD–14 6354, FK5 861, HD 216032, HIP 112716, HR 8679, NSV 14329, SAO 165321.^[6]