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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 148 light-years (45 parsecs) 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]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Corona Australis |
| Right ascension | 18h 13m 59.67590s[1] |
| Declination | –42° 34′ 31.3558″[1] |
| Apparent magnitude (V) | +9.33[2] |
| Characteristics | |
| Spectral type | K0IV/V[3] |
| B−V color index | 0.861±0.032[2] |
| Astrometry | |
| Radial velocity (Rv) | −17.51±0.20[1] km/s |
| Proper motion (μ) | RA: +36.061 mas/yr[1] Dec.: –80.180 mas/yr[1] |
| Parallax (π) | 22.0344 ± 0.0177 mas[1] |
| Distance | 148.0 ± 0.1 ly (45.38 ± 0.04 pc) |
| Absolute magnitude (MV) | 6.20[2] |
| Details[4] | |
| Mass | 0.81±0.02 M☉ |
| Radius | 0.80+0.01 −0.02[5] R☉ |
| Luminosity | 0.388±0.001[5] L☉ |
| Surface gravity (log g) | 4.43±0.08 cgs |
| Temperature | 5,101+50 −41[5] K |
| Metallicity [Fe/H] | −0.09±0.03 dex |
| Age | 4.0±3.8 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
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.[4] The age of the star is poorly constrained, but it is spinning slowly with a period of around 30 days.[4] It has 81% of the mass of the Sun and 80%[4] of the Sun's girth. The star is radiating 39%[5] of the luminosity of the Sun from its photosphere at an effective temperature of 5,101 K.[4]
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.[4] In 2023, the inclination and true mass of HD 166724 b were determined via astrometry.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 3.8+0.65 −0.29 MJ |
5.17+0.38 −0.49 |
13.0+1.4 −1.8 |
0.729+0.018 −0.017 |
68+15 −16 or 112+16 −15° |
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