HD 30856

HD 30856 A is an evolved star in the red-giant branch, with a spectral type of K0 III, a radius of 4.4 R_☉, and a mass of 1.17 M_☉. The surface temperature of HD 30856 is estimated to be about 4,895 K, which gives it an orange color. The star is roughly 10 times as bright as the Sun, which, combined with a distance of 429 light-years, places its apparent magnitude at 7.91,^[3][5][6] too dim to be visible from Earth by the naked eye.^[8] The star is aged approximately 3.8 billion years,^[6] making it younger than the Sun (4.6 billion years old^[9]).

In 2019, the People's Republic of Burkina Faso was assigned to giving the HD 30856 A system a proper name as part of the IAU100 NameExoWorlds Project,^[2] planned to celebrate the hundredth anniversary of the International Astronomical Union (IAU), which grants the right to name an exoplanetary system to every state and territory in the world. Names were submitted and selected within Burkina Faso, which were then presented to the IAU to be officially recognized.^[13] On 17 December 2019, the IAU announced that HD 30856 A and its planet, b, were named Mouhoun and Nakanbé, respectively.^[7]

Mouhoun is named after the Black Volta (locally called Mouhoun), Burkina Faso's largest river that serves a crucial societal role in the western part of the country. Nakanbé is the native name for the White Volta, the second largest river in the nation with its source located in the Sahel region.^[7]

In 2011, radial-velocity observations made at the W. M. Keck Observatory revealed the existence of one exoplanet around HD 30856 A.^[6] The planet, HD 30856 Ab, is thought to be a gas giant at least 1.5 times the mass of Jupiter, which orbits its host star at a distance of 1.85 AU once every 847 days (2.32 years).^[5] Its orbit is nearly circular (i.e., with a low eccentricity),^[5] similar to planets in the Solar System.^[14]