HD 173416

HD 173416, also named Xihe, is a star with an orbiting exoplanet in the northern constellation of Lyra. It is located at a distance of approximately 433 light years based on parallax measurements, but is drifting closer to the Sun with a radial velocity of −61 km/s. It has a bright absolute magnitude of 0.406, but a much fainter apparent visual magnitude of 6.04. This indicates the star is dimly visible to the naked eye.

The spectrum of HD 173416 indicates this is an evolved G-type giant star with a stellar classification of G8 III. This means it has consumed the hydrogen at its stellar core and evolved off the main sequence. At an age of around two billion years, it has expanded to 13 times the radius of the Sun. The star has 1.8 times the mass of the Sun and is radiating 79 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,790 K. Based on the abundance of iron in the stellar atmosphere, it has a sub-solar metallicity.

The star HD 173416 is named Xihe (羲和). The name was selected in the NameExoWorlds campaign by Nanjing, during the 100th anniversary of the IAU. Xihe is the goddess of the sun in the Chinese mythology and also represents the earliest astronomers and developers of calendars in ancient China. The exoplanet is named Wangshu (望舒) after the goddess who drives the Moon across the sky in Chinese mythology.

Planetary system
In January 2009, an exoplanet of the star was discovered. This object was detected using the radial velocity method by search programs conducted from the Xinglong Station in China and the Okayama Astrophysical Observatory (OAO) in Japan. As the inclination of the orbital plane is unknown, only a lower bound on the mass can be determined. The mass of this object is at least 2.7 times the mass of Jupiter.