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]
| 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 |
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]
Planetary system
editIn 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° |
— |
References
edit- ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d e f g h i Hojjatpanah, S.; et al. (2019). "Catalog for the ESPRESSO blind radial velocity exoplanet survey". Astronomy & Astrophysics. 629: A80. arXiv:1908.04627. Bibcode:2019A&A...629A..80H. doi:10.1051/0004-6361/201834729. S2CID 199552090.
- ^ Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
- ^ a b c Jones, M. I.; et al. (2015). "A planetary system and a highly eccentric brown dwarf around the giant stars HIP 67851 and HIP 97233". Astronomy & Astrophysics. 573: A3. arXiv:1409.7429. Bibcode:2015A&A...573A...3J. doi:10.1051/0004-6361/201424771. S2CID 53638707.
- ^ Anderson, E.; Francis, Ch. (2012-05-01). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
- ^ a b Sousa, S. G.; et al. (2018). "SWEET-Cat updated". Astronomy & Astrophysics. 620: A58. arXiv:1810.08108. Bibcode:2018A&A...620A..58S. doi:10.1051/0004-6361/201833350. S2CID 119374557.
- ^ a b c d e f Soto, M. G.; et al. (2021). "SPECIES. II. Stellar parameters of the EXPRESS giant star sample". Astronomy and Astrophysics. 647: A157. arXiv:2009.03371. Bibcode:2021A&A...647A.157S. doi:10.1051/0004-6361/202039357. S2CID 221534230.
- ^ "HD 121056". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-05-13.
- ^ a b Wittenmyer, Robert A.; et al. (2015). "The Pan-Pacific Planet Search. Ii. Confirmation of a Two-Planet System Around Hd 121056". The Astrophysical Journal. 800 (1): 74. arXiv:1412.6889. Bibcode:2015ApJ...800...74W. doi:10.1088/0004-637X/800/1/74. S2CID 53684180.
- ^ Kane, Stephen R.; et al. (2019). "Predicting multiple planet stability and habitable zone companions in the TESS era". Monthly Notices of the Royal Astronomical Society. 485 (4): 4703–4725. arXiv:1901.11297. Bibcode:2019MNRAS.485.4703A. doi:10.1093/mnras/stz345.
- ^ Saillenfest, M.; et al. (2019). "Secular spin-axis dynamics of exoplanets". Astronomy & Astrophysics. 623: A4. arXiv:1901.02831. Bibcode:2019A&A...623A...4S. doi:10.1051/0004-6361/201834344. S2CID 119073661.
- ^ a b Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.
- ^ Martinache, Frantz; Ireland, Michael J. (2018). "Kernel-nulling for a robust direct interferometric detection of extrasolar planets". Astronomy & Astrophysics. 619: A87. arXiv:1802.06252. Bibcode:2018A&A...619A..87M. doi:10.1051/0004-6361/201832847. S2CID 118882482.