HD 171238

HD 171238 is a star with an orbiting exoplanet in the southern constellation of Sagittarius. It is located at a distance of 145 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of 21 km/s. The star has an absolute magnitude of 5.15, but at the distance of this system it is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.61.

The spectrum of HD 171238 presents as an ordinary G-type main-sequence star with a stellar classification of G8 V. At an estimated age of around four billion years, it is spinning with a projected rotational velocity of 1.5 km/s. The metallicity of the star – the abundance of elements more massive than helium – is 48% higher than solar, based on the abundance of iron. There are indications of a significant level of magnetic activity in the chromosphere. The star has 99% of the mass of the Sun and 95% of the Sun's girth. It is radiating just 77% of the luminosity of the Sun from its photosphere at an effective temperature of 5,570 K.

Planetary system
In August 2009, it was announced that this star has a super-jovian exoplanet. Using astrometry from Gaia, astronomers were able to deduce the true mass of HD 171238 b as ; higher than the minimum mass estimated from Doppler spectroscopy.