# 98 Aquarii

Observation data Epoch J2000      Equinox J2000 Constellation Location of 98 Aquarii (circled) Aquarius 23h 22m 58.22606s[1] –20° 06′ 02.0963″[1] +3.97[2] K0 III[3] +0.948[2] +1.089[2] Radial velocity (Rv) –6.5[4] km/s Proper motion (μ) RA: –121.28[1] mas/yr Dec.: –97.59[1] mas/yr Parallax (π) 19.96 ± 0.23[1] mas Distance 163 ± 2 ly (50.1 ± 0.6 pc) Mass 2.1[5] M☉ Radius 14[6] R☉ Surface gravity (log g) 2.4[5] cgs Temperature 4,630[5] K Metallicity [Fe/H] –0.30[5] dex BD–20 6587, FK5 1612, HD 220321, HIP 115438, HR 8892, SAO 191858.[7] SIMBAD data

98 Aquarii (abbreviated 98 Aqr) is a star in the equatorial constellation of Aquarius. 98 Aquarii is the Flamsteed designation, although it also bears the Bayer designation b1 Aquarii. It is visible to the naked eye with an apparent visual magnitude of +3.97.[2] The distance to this star, 163 light-years (50 parsecs), is known from parallax measurements made with the Hipparcos spacecraft.[1]

With over double the mass of the Sun,[5] this is an evolved giant star that has a stellar classification of K0 III.[3] The measured angular diameter of this star is 2.54 ± 0.13 mas.[8] At the estimated distance of 98 Aquarii,[1] this yields a physical size of about 14 times the radius of the Sun.[6] The expanded outer envelope has an effective temperature of 4,630 K,[5] giving it the orange glow of a K-type star.[9]

## References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:, 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, doi:10.1093/mnras/172.3.667.
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. ^ 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. Melo, C. H. F.; et al. (August 2005), "On the nature of lithium-rich giant stars. Constraints from beryllium abundances", Astronomy and Astrophysics, 439 (1): 227–235, arXiv:, Bibcode:2005A&A...439..227M, doi:10.1051/0004-6361:20041805.
6. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1.. The radius (R*) is given by:
{\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(50.1\cdot 2.54\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 27.4\cdot R_{\bigodot }\end{aligned}}}
7. ^ "* 98 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-05.
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.
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.