| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus[1] |
| Right ascension | 13h 55m 42.7120s[2] |
| Declination | −32° 09′ 34.616″[2] |
| Apparent magnitude (V) | 10.91[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | F7[4] |
| Apparent magnitude (B) | ~11.3[5] |
| Apparent magnitude (R) | ~11.0[5] |
| Apparent magnitude (J) | 9.956 ± 0.023[5] |
| Apparent magnitude (H) | 9.713 ± 0.025[5] |
| Apparent magnitude (K) | 9.693 ± 0.023[5] |
| Astrometry | |
| Radial velocity (Rv) | −2.42±0.43[2] km/s |
| Proper motion (μ) | RA: 8.723mas/yr[2] Dec.: −22.328mas/yr[2] |
| Parallax (π) | 3.4891±0.0176 mas[2] |
| Distance | 935 ± 5 ly (287 ± 1 pc) |
| Details[6] | |
| Mass | 1.18±0.12 M☉ |
| Radius | 1.477±0.072 R☉ |
| Luminosity | 3.09±0.34 L☉ |
| Surface gravity (log g) | 4.169±0.033 cgs |
| Temperature | 6300±100 K |
| Metallicity[Fe/H] | −0.17±0.11 dex |
| Rotational velocity (v sin i) | 4±2 km/s |
| Age | 3.9+2.8 −1.3 Gyr |
| Other designations | |
| Nyamien,CD−31 10766,TOI-820,TIC 111991770,WASP-15,TYC 7283-1162-1,2MASS J13554270-3209345[5] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
WASP-15, also namedNyamien, is amagnitude 11star located about 935light-years away in theconstellationCentaurus.[5] The star, which is more massive, larger, hotter, and more luminous than theSun, is also less metal-rich than the Sun. WASP-15 has one known planet in its orbit,WASP-15b; the planet is ahot Jupiter with an anomalously high radius, a phenomenon which may be explained by the presence of an internal heat source.[6] The star was first observed by theSuperWASP program in 2006; future measurements in 2007 and 2008, as well as follow-up observations and analysis, eventually led to the discovery of WASP-15b using thetransit method andDoppler spectroscopy.[6]
WASP-15 was first observed from theSouth African Astronomical Observatory, which hosts the planet-searchingSuperWASP program in the Southern Hemisphere (WASP-South), and was catalogued by its brightness and its coordinates in the sky. This information was captured first with one camera field between May 4, 2006 and July 17, 2006, and later again using two overlapping camera fields between January 31, 2007 to July 7, 2007 and from January 31, 2008 to May 29, 2008.[6]
Data processing led to the acquisition of 24,943 data points that suggested that some bodytransited, or crossed in front of (and briefly dimmed), WASP-15 every 3.7520 days. Approximately eleven transits, full and partial, were observed. Use of theEulerCAM photometer at theLa Silla Observatory's 1.2 mLeonhard Euler Telescope on March 29, 2008 provided further evidence for an exoplanet by better defining the transit's curve. Later, theCORALIE spectrograph (also on the Euler telescope) between March 6, 2008 and July 17, 2008 usedDoppler spectroscopy to collect 21 radial velocity measurements. Analysis confirmed the presence of a planet that was later designatedWASP-15b.[6]
WASP-15, and its planet WASP-15b, were chosen as part of the 2019NameExoWorlds campaign organised by theInternational Astronomical Union, which assigned each country a star and planet to be named. WASP-15 was assigned toIvory Coast. The winning proposal named the star Nyamien refers to the supreme creator deity ofAkan mythology, and the planet Asye refers to the Earth goddess of Akan mythology.[7][8][9]
WASP-15 is anF-type star with amass that is 1.18 times larger than the Sun, and aradius that is 1.477 bigger. It is, thus, larger, more massive, and more diffuse than the Sun. The star has aneffective temperature of 6300K, making it also hotter than the Sun.[10] With ametallicity of [Fe/H] = -0.17, WASP-15 has 0.676 times the amount of iron than the Sun, and has consistently lower levels of other metals, including sodium, magnesium, silicon, calcium, and scandium.[6] In addition, WASP-15 is most likely younger than the Sun, as it has an estimated age of 3.9 billion years.[10] WASP-15 is approximately 3.09 times moreluminous than the Sun.[6]
WASP-15 is located at a distance of approximately 287parsecs (940light-years),[2] and it has an estimatedapparent magnitude of 10.9. It is, thus, not visible from Earth with the unaided eye.[10]
WASP-15 is host to the planetWASP-15b. The planet, which is aHot Jupiter, orbits its host star at a distance of 0.0499AU every 3.7520656 days. WASP-15b was noted by its discoverers because of its anomalously high radius, which is 1.428 times that of Jupiter, compared to its mass, which is 0.542 times the size of Jupiter.[10] WASP-15b's large radius cannot be explained solely by its proximity to its star, suggesting that some form oftidal heating or other internal heating mechanism is also involved.[6]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Asye | 0.542+0.054 −0.053 MJ | 0.0499+0.0017 −0.0018 | 3.75209748(81) | <0.055 | 85.5±0.5° | 1.428±0.077 RJ |
