Astronomy:HD 120084
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 13h 42m 39.20162s[1] |
| Declination | +78° 03′ 51.9800″[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(31)[1] mas/yr Dec.: 46.164(33)[1] mas/yr |
| Parallax (π) | 9.6277 ± 0.0258[1] mas |
| 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 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | 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] This planet has one of the most eccentric orbits discovered around an evolved star,[2] with published estimates of the eccentricity ranging from 0.48[7] to 0.73.[8] In 2022, the inclination and true mass of HD 120084 b were measured via astrometry,[8] with two more astrometric orbital solutions published in 2023.[9][7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 6.4+2.9 −1.9 MJ |
4.21+0.17 −0.19 |
5.864+0.024 −0.026 |
0.483+0.027 −0.029 |
38+22 −12 or 139+15 −29° |
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References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 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. doi:10.1093/pasj/65.4.85. Bibcode: 2013PASJ...65...85S. https://academic.oup.com/pasj/article/65/4/85/1531866/.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 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" (in en). The Astrophysical Journal Letters 971 (2): L50. doi:10.3847/2041-8213/ad6c49. ISSN 2041-8205. Bibcode: 2024ApJ...971L..50L.
- ↑ 4.0 4.1 4.2 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. doi:10.1051/0004-6361/201629967. Bibcode: 2017A&A...600A..69A.
- ↑ "HD 120084". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+120084.
- ↑ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y. Retrieved 2013-02-20.
- ↑ 7.0 7.1 7.2 Teng, Huan-Yu et al. (August 2023). "Revisiting planetary systems in the Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and a multiplicity-metallicity trend around evolved stars". Publications of the Astronomical Society of Japan 75 (6): 1030–1071. doi:10.1093/pasj/psad056. Bibcode: 2023PASJ...75.1030T.
- ↑ 8.0 8.1 Feng, Fabo et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series 262 (21): 21. doi:10.3847/1538-4365/ac7e57. Bibcode: 2022ApJS..262...21F.
- ↑ Xiao, Guang-Yao et al. (May 2023). "The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements". Research in Astronomy and Astrophysics 23 (5): 055022. doi:10.1088/1674-4527/accb7e. Bibcode: 2023RAA....23e5022X.
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