Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Centaurus |
Right ascension | 13h 53m 52.06131s [1] |
Declination | −35° 18′ 51.6918″ [1] |
Apparent magnitude (V) | 6.17 [2] |
Characteristics | |
Evolutionary stage | giant star |
Spectral type | K0 III [3] |
B−V color index | 1.01 [4] |
Astrometry | |
Radial velocity (Rv) | 5.60±0.13 [1] km/s |
Proper motion (μ) |
RA: −295.304±0.040
mas/
yr
[1] Dec.: −68.458±0.058 mas/ yr [1] |
Parallax (π) | 15.6261 ± 0.0418 mas [1] |
Distance | 208.7 ± 0.6
ly (64.0 ± 0.2 pc) |
Absolute magnitude (MV) | +2.08 [5] |
Details | |
Mass | 1.60±0.18 [6] M☉ |
Radius | 5.72 [7] R☉ |
Luminosity | 15.8 [7] L☉ |
Surface gravity (log g) | 3.261±0.105 [2] cgs |
Temperature | 4,867±49 [2] K |
Metallicity | [Mg/H] 0.286±0.05 dex [2] |
Metallicity [Fe/H] | 0.020±0.031 [2] dex |
Rotational velocity (v sin i) | 2.38±0.51 [2] km/s |
Age | 5.46 [7] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
HD 121056, or HIP 67851, is an aging giant star with a pair of orbiting exoplanets located in the southern constellation of Centaurus. This star is dimly visible to the naked eye with an apparent visual magnitude of 6.17. [2] It is located at a distance of 209 light years from the Sun, based on parallax measurements, and is drifting further away with a radial velocity of 5.6 km/s. [1]
The spectrum of HD 121056 presents as an evolved K-type giant star with a stellar classification of K0 III. [9] It is presently ascending the red-giant branch, having exhausted the supply of hydrogen at its core. [4] The star is about 5.5 [7] billion years old and is spinning with a projected rotational velocity of 2.4 km/s. HD 121056’s concentration of heavy elements is similar to the Sun, with a metallicity Fe/H index of 0.020±0.031, although the star is enriched in lighter rock-forming elements like magnesium and aluminum. [2] It has 1.6 [6] 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 enlarged photosphere at an effective temperature of 4,867 K. [2]
In 2014, two planets orbiting HD 121056 were discovered by the radial velocity method, [4] and were confirmed a few months later. [9] The orbits of these planets are stable on astronomical timescales, [10] although the periods are not in orbital resonance. [11] In 2022, the inclination and true mass of HD 121056 c were measured via astrometry. [12]
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. [13]
Companion (in order from star) |
Mass |
Semimajor axis ( AU) |
Orbital period ( days) |
Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | ≥ 1.568+0.071 −0.072 MJ |
0.482+0.009 −0.010 |
88.9±0.1 | 0.063+0.031 −0.032 |
— | — |
c | 6.937+2.045 −0.518 MJ |
6.032+0.651 −0.362 |
3,923.7+617.5 −330.2 |
0.356+0.112 −0.085 |
89.863+28.378 −24.730 ° |
— |