HD 166724

HD 166724 is a star in the southern constellation of Corona Australis. It is invisible to the naked eye with an apparent visual magnitude of +9.33.[2] The star is located at a distance of 147 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −18 km/s.[1] It is predicted to come as close as 97.0 light-years in around 1.2 million years from now.[2] The star has an absolute magnitude of 6.20.[2]

HD 166724
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Corona Australis
Right ascension 18h 13m 59.67583s[1]
Declination –42° 34′ 31.3562″[1]
Apparent magnitude (V) +9.33[2]
Spectral type K0IV/V[3]
B−V color index 0.861±0.032[2]
Radial velocity (Rv)−17.84±0.65[1] km/s
Proper motion (μ) RA: +36.110[1] mas/yr
Dec.: –80.147[1] mas/yr
Parallax (π)22.1273 ± 0.0439[4] mas
Distance147.4 ± 0.3 ly
(45.19 ± 0.09 pc)
Absolute magnitude (MV)6.20[2]
Mass0.81±0.02 M
[1] R
Luminosity0.388±0.001[1] L
Surface gravity (log g)4.43±0.08 cgs
[1] K
Metallicity [Fe/H]−0.09±0.03 dex
Age4.0±3.8 Gyr
Other designations
CD–42° 13019, HD 166724, HIP 89354[6]
Database references
Exoplanet Archivedata
Extrasolar Planets

The stellar classification of HD 166724 is K0IV/V,[3] showing blended features of a K-type main-sequence star with a more evolved subgiant star. It is slightly active with chromospheric activity being demonstrated by an emission peak in the Ca II K absorption line.[5] The age of the star is poorly constrained, but it is spinning slowly with a period of around 30 days.[5] It has 81% of the mass of the Sun and 80%[5] of the Sun's girth. The star is radiating 39%[1] of the luminosity of the Sun from its photosphere at an effective temperature of 5,101 K.[5]

Planetary systemEdit

From 1998 to 2012, the star was under observance from "the CORALIE echelle spectrograph at La Silla Observatory". In 2012, a long-period, wide-orbiting exoplanet was deduced by radial velocity variations. This was published in November. The discoverers noted that HD 166724 b is among "the three most eccentric planets with a period larger than 5 years" alongside HD 98649 b and HD 219077 b; but unlike them, too dim as a candidate for direct imaging with current technology. The reason for this high orbital eccentricity is unknown.[5]

The HD 166724 planetary system[7]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b >3.53 ± 0.11 MJ 5.42 ± 0.43 5144+705
0.734 ± 0.020


  1. ^ a b c d e f g h i j 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 d e f 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.
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H
  4. ^ van Leeuwen, F. (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. S2CID 18759600.Vizier catalog entry
  5. ^ a b c d e f Marmier, M.; et al. (2013). "The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets". Astronomy and Astrophysics. 551. A90. arXiv:1211.6444. Bibcode:2013A&A...551A..90M. doi:10.1051/0004-6361/201219639. S2CID 59467665.
  6. ^ "HD 166724". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-03-21.
  7. ^ "hd_166724_b".