HD 120084
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 13h 42m 39.201616s[1] |
| Declination | +78° 03′ 51.979994″[1] |
| Apparent magnitude (V) | 5.91[2] |
| Characteristics | |
| Evolutionary stage | Red clump[3] |
| Spectral type | G7III[2] |
| B−V color index | 1.000[2] |
| Astrometry | |
| Radial velocity (Rv) | −8.97±0.13[1] km/s |
| Proper motion (μ) | RA: −64.900±0.031 mas/yr[1] Dec.: 46.164±0.033 mas/yr[1] |
| Parallax (π) | 9.6277±0.0258 mas[1] |
| Distance | 338.8 ± 0.9 ly (103.9 ± 0.3 pc) |
| Absolute magnitude (MV) | +0.96[2] |
| Details | |
| Mass | 2.661±0.335[3] M☉ |
| Radius | 11.03±0.65[3] R☉ |
| Luminosity | 63+8 −7[3] L☉ |
| Surface gravity (log g) | 2.779±0.075[3] cgs |
| Temperature | 4,969±40[4] K |
| Metallicity [Fe/H] | 0.12±0.03[4] dex |
| Rotational velocity (v sin i) | 2.44[2] km/s |
| Other designations | |
| BD+78°466, FK5 3090, HIP 66903, SAO 7876[5] | |
| Database references | |
| SIMBAD | data |
HD 120084 is a star with an orbiting exoplanet[2] in the northern constellation of Ursa Minor. With an apparent magnitude of 5.91,[2] it is just visible to the naked eye in suburban skies.[6] The distance to this system is 339 light years based on parallax measurements, but it is drifting closer to the Sun with a radial velocity of −9 km/s.[1]
The spectrum of this star matches a type of G7III, indicating it is a G-type giant, an evolved star that used up its hydrogen fuel and has expanded.[2] After undergoing a helium flash, it is now in the red clump stage generating energy through the fusion of helium.[3] It has 2.7 times the mass of the Sun and a radius about 11 times the radius of the Sun. It radiates 60 times the Sun's luminosity from its photosphere at an effective temperature of around 4,969 K.[2][4]
Planetary system
A gas giant planet was discovered in 2013 using Doppler spectroscopy, named HD 120084 b.[2] With an orbital eccentricity of 0.73,[7] this planet has one of the most eccentric orbits discovered.[2] In 2022, the inclination and true mass of HD 120084 b were measured via astrometry.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 5.762+4.638 −0.285 MJ |
4.341+0.133 −0.155 |
5.709+0.057 −0.088 |
0.732±0.123 | 110.934+33.840 −60.717° |
— |
References
- ^ 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 j k Sato, Bun’ei; et al. (2013). "Planetary Companions to Three Evolved Intermediate-Mass Stars: HD 2952, HD 120084, and ω Serpentis". Publications of the Astronomical Society of Japan. 65 (4). 85. arXiv:1304.4328. Bibcode:2013PASJ...65...85S. doi:10.1093/pasj/65.4.85.
- ^ a b c d e f Lin, Wen-Xu; Qian, Sheng-Bang; Zhu, Li-Ying (2024-08-09). "Revealing the Fate of Exoplanet Systems: Asteroseismic Identification of Host Star in the Red Clump or Red Giant Branch". The Astrophysical Journal Letters. 971 (2): L50. arXiv:2408.04947. Bibcode:2024ApJ...971L..50L. doi:10.3847/2041-8213/ad6c49. ISSN 2041-8205.
- ^ a b c Andreasen, D. T.; et al. (2017). "SWEET-Cat update and FASMA A new minimization procedure for stellar parameters using high-quality spectra". Astronomy & Astrophysics. A69: 600. arXiv:1703.06671. Bibcode:2017A&A...600A..69A. doi:10.1051/0004-6361/201629967. S2CID 119534579.
- ^ "HD 120084". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-07.
- ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Archived from the original on 2014-03-31. Retrieved 2013-02-20.
- ^ a b c 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.
