  | |
| Observation data Epoch J2000.0[1] Equinox J2000.0[1] | |
|---|---|
| Constellation | Eridanus[2] |
| Right ascension | 04h 50m 17.8614408264s[1] |
| Declination | −24° 22′ 07.833769068″[1] |
| Apparent magnitude (V) | 7.911[1][3] |
| Characteristics | |
| Evolutionary stage | Red-giant branch star[1] |
| Spectral type | K0III[1][3] |
| B−Vcolor index | 0.961[1][3] |
| Astrometry | |
| Radial velocity (Rv) | 35.71[1] km/s |
| Proper motion (μ) | RA: 18.469[1]mas/yr Dec.: −19.837[1]mas/yr |
| Parallax (π) | 7.5965±0.0179 mas[1] |
| Distance | 429 ± 1 ly (131.6 ± 0.3 pc) |
| Orbit[4] | |
| Primary | HD 30856 A |
| Companion | HD 30856 B |
| Semi-major axis (a) | 0.786″ |
| Details | |
| HD 30856 A | |
| Mass | 1.17[5] / 1.35[4] M☉ |
| Radius | 4.40[5] R☉ |
| Luminosity | 9.9±0.5[6] L☉ |
| Surface gravity (log g) | 3.20[5] cgs |
| Temperature | 4895[5] / 4982 ± 44[4] K |
| Metallicity [Fe/H] | −0.06±0.03[6] dex |
| Rotational velocity (v sin i) | 2.85[6] km/s |
| HD 30856 B | |
| Mass | 0.54±0.01[4] M☉ |
| Surface gravity (log g) | 4.7[4] cgs |
| Temperature | 3700–4150[4] K |
| Other designations | |
| CD−24 2616,Gaia DR3 4893980371818915456,HD 30856,HIP 22491,SAO 169805,TIC 612908,TYC 6466-1769-1,GSC 06466-01769,2MASS J04501787-2422077[1] | |
| Database references | |
| SIMBAD | data |
HD 30856 (proper nameMouhoun) is abinary system between HD 30856 A (often simply HD 30856[6][7]), aK-typegiant star, and HD 30856 B, ared dwarf companion, located in the constellation ofEridanus about 430light-years distant.[2][1] Asuper-Jupiterexoplanet, HD 30856 b (proper name Nakanbé), is known to orbit the primary star.[6]
HD 30856 A is an evolved star in thered-giant branch, with a spectral type of K0 III, a radius of 4.4R☉, and a mass of 1.17M☉. The surface temperature of HD 30856 is estimated to be about 4,895K, which gives it an orange color. The star is roughly 10 times as bright as theSun, which, combined with a distance of 429 light-years, places itsapparent magnitude at 7.91,[3][5][6] too dim to be visible fromEarth by the naked eye.[8] The star is aged approximately 3.8billion years,[6] making it younger than the Sun (4.6 billion years old[9]).
Through the use ofadaptive optics, observations at theKeck II telescope in Hawaii revealed the existence of another star, designated HD 30856 B, about 0.8arcseconds east-southeast of HD 30856.[4] HD 30856 B has a mass of 0.54M☉ and a temperature of 3700–4150 K,[4][a] typical for anM0V–M1V red dwarf.[10][11][12][b]
Since the star shares a very similarproper motion with HD 30856 A, the two stars are believed to be in a binary system. HD 30856 B revolves around the primary star (A) in a wide orbit, with asemi-major axis of 93 ± 8AU.[4]
In 2019, thePeople's Republic of Burkina Faso was assigned to giving the HD 30856 A system a proper name as part of theIAU100 NameExoWorlds Project,[2] planned to celebrate the hundredth anniversary of theInternational 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 theBlack 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 theWhite Volta, the second largest river in the nation with its source located in theSahel region.[7]
In 2011,radial-velocity observations made at theW. M. Keck Observatory revealed the existence of one exoplanet around HD 30856 A.[6] The planet, HD 30856 Ab, is thought to be agas giant at least 1.5 times the mass ofJupiter, which orbits its host star at a distance of 1.85AU once every 847 days (2.32 years).[5] Its orbit is nearly circular (i.e., with a loweccentricity),[5] similar to planets in theSolar System.[14]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| HD 30856 Ab (Nakanbé) | >1.547 MJ | 1.85 | 847.468 ± 19.811 | 0.061 ± 0.058 | — | 1.228 RJ |
| Stars |
| ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||||
| Nebulae |
| ||||||||||||
| Galaxies |
| ||||||||||||
| |||||||||||||
| |||||||||||||
2011 in space | ||
|---|---|---|
2012 » | ||
Space probe launches |
|   .jpg) |
| SelectedNEOs | ||
| Exoplanets |
| |
| Discoveries | ||
| Novae | ||
| Comets | ||
| Space exploration | ||
