| Discovery | |
|---|---|
| Discovered by | Vogt et al. |
| Discovery site |  California, United States |
| Discovery date | June 24, 2005 |
| Doppler spectroscopy | |
| Orbital characteristics[1] | |
| Apastron | 2.02 AU (302,000,000 km) |
| Periastron | 1.46 AU (218,000,000 km) |
| 1.740 ± 0.010 AU (260,300,000 ± 1,500,000 km) | |
| Eccentricity | 0.159±0.006 |
| 921.538 ± 1.15 d (2.52303 ± 0.00315 a) | |
Average orbital speed | 20.7 |
| Inclination | 55.950±14.553 |
| 229.392±14.473 | |
| 2449565.615±18.01 | |
| 15.445±6.87 | |
| Semi-amplitude | 74.799±1.497 |
| Star | HD 128311 |
| Physical characteristics[1] | |
| Mass | 3.789+0.924 −0.432 MJ |
HD 128311 c is an exoplanet located approximately 54 light-years away in the constellation of Boötes. This planet orbits in an eccentric orbit at 1.74 AU from its star (HD 128311). The planet has a minimum mass of 3.22 MJ,[2] and astrometric observations in 2014 revealed its true mass to be 3.789 MJ.[1]