| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Centaurus[1] |
| Right ascension | 13h 53m 52.06131s[2] |
| Declination | −35° 18′ 51.6918″[2] |
| Apparent magnitude (V) | 6.17[3] |
| Characteristics | |
| Evolutionary stage | red giant branch[2] |
| Spectral type | K0 III[4] |
| B−Vcolor index | 1.01[5] |
| Astrometry | |
| Radial velocity (Rv) | 5.60±0.13[2] km/s |
| Proper motion (μ) | RA: −295.304mas/yr[2] Dec.: −68.458mas/yr[2] |
| Parallax (π) | 15.6261±0.0418 mas[2] |
| Distance | 208.7 ± 0.6 ly (64.0 ± 0.2 pc) |
| Absolute magnitude (MV) | +2.08[1] |
| Details | |
| Mass | 1.394±0.052[6] M☉ |
| Radius | 5.948±0.077[6] R☉ |
| Luminosity | 18.2+2.0 −1.8[6] L☉ |
| Surface gravity (log g) | 3.034±0.005[6] cgs |
| Temperature | 4,867±49[3] K |
| Metallicity | [Mg/H]0.286±0.05 dex[3] |
| Metallicity[Fe/H] | 0.020±0.031[3] dex |
| Rotational velocity (v sin i) | 2.38±0.51[3] km/s |
| Age | 5.46[7] Gyr |
| Other designations | |
| CD−34 9223,GJ 532.1,HD 121056,HIP 67851,HR 5224,TYC 7287-1874-1,2MASS J13535209-3518517[8] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 121056, orHIP 67851, is an aginggiant star with a pair of orbitingexoplanets located in the southernconstellation ofCentaurus. This star is dimly visible to the naked eye with anapparent visual magnitude of 6.17.[3] It is located at a distance of 209 light-years from the Sun, based onparallax measurements, and is drifting further away with aradial velocity of 5.6 km/s.[2]
Thespectrum of HD 121056 presents as anevolvedK-typegiant star with astellar classification of K0 III.[9] It is presently ascending thered-giant branch, having exhausted the supply of hydrogen at itscore.[5] The star is about 5.5[7] billion years old and is spinning with aprojected rotational velocity of 2.4 km/s. HD 121056’s concentration of heavy elements is similar to theSun, with ametallicity Fe/H index of 0.020±0.031, although the star is enriched in lighter rock-forming elements like magnesium and aluminum.[3] It has 1.6[10] times the mass of the Sun and has expanded to 5.72 times the Sun's radius.[7] The star is radiating 15.8[7] times the luminosity of the Sun from its enlargedphotosphere at aneffective temperature of 4,867 K.[3]
In 2014, two planets orbiting HD 121056 were discovered by theradial velocity method,[5] and were confirmed a few months later.[9] The orbits of these planets are stable on astronomical timescales,[11] although the periods are not inorbital resonance.[12] In 2022, the inclination and true mass of HD 121056 c were measured viaastrometry, indicating a nearly edge-on orbit.[13] Subsequent studies have provided further updates to the planetary parameters.[6][14]
The planetary system configuration is favorable for direct imaging of exoplanets in the near future, being included in the top ten easiest targets in 2018.[15]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥1.15±0.04 MJ | 0.42±0.0002 | 89.23±0.06 | 0.13±0.04 | — | — |
| c | 4.97+0.22 −0.21 MJ | 4.55±0.05 | 3,128.41+52.09 −47.13 | 0.30±0.03 | 89.86+28.38 −24.73[13]° | — |
