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]

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]

Planetary system

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]

References