HD 20782
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Fornax
Right ascension 03h 20m 03.57776s[1]
Declination −28° 51′ 14.6604″[1]
Apparent magnitude (V) 7.38[2]
Characteristics
Spectral type G1.5 V[3]
B−V color index +0.65[2]
Astrometry
Radial velocity (Rv)40.7±0.99[4] km/s
Proper motion (μ) RA: +349.054 mas/yr[1]
Dec.: −65.305 mas/yr[1]
Parallax (π)27.8760 ± 0.0172 mas[1]
Distance117.00 ± 0.07 ly
(35.87 ± 0.02 pc)
Absolute magnitude (MV)+4.61[5]
Details
Mass0.96+0.02
−0.01[6] M☉
Radius1.17±0.03[7] R☉
Luminosity1.262+0.005
−0.006[1] L☉
Surface gravity (log g)4.35+0.05
−0.08[8] cgs
Temperature5,741±41[6] K
Metallicity [Fe/H]−0.06±0.02[9] dex
Rotational velocity (v sin i)3.0±0.6[10] km/s
Age8.5+2.5
−2.0[9] Gyr
Other designations
CD−29°1231, CPD−29°382, HD 20782, HIP 15527, SAO 168469, WDS J03201-2851A, LTT 1582, TIC 144503325[11]
Database references
SIMBADdata
Exoplanet Archivedata

HD 20782 (HIP 15527; LTT 1582) is the primary of a wide binary system located in the southern constellation Fornax. It has an apparent magnitude of 7.38,[2] making it readily visible in binoculars but not to the naked eye. The system is located relatively close at a distance of 117 light-years based on Gaia DR3 parallax measurements,[1] but it is receding with a heliocentric radial velocity of 40.7 km/s.[4] At its current distance, HD 20782's brightness is diminished by 0.12 magnitudes due to interstellar extinction[12] and it has an absolute magnitude of +4.61.[5]

Properties

HD 20782 has a stellar classification of G1.5 V,[3] indicating that it is an ordinary G-type main-sequence star like our Sun. It has also been given a cooler class of G3 V. It has 96% the mass of the Sun[6] and 1.17 times the radius of the Sun.[7] It radiates 1.262 times the luminosity of the Sun[1] from its photosphere at an effective temperature of 5,741 K,[6] which is 35 K cooler than the Sun's temperature. When viewed in the night sky. the star has a yellow hue. HD 20782 is slightly metal deficient with an iron abundance 87.1% that of the Sun's or [Fe/H] = −0.06,[9] and it is estimated to be 8.5 billion years old,[9] which is nearly twice of the Sun's age. It spins modestly with a projected rotational velocity of 3.0 km/s.[10]

Binary System

HD 20781 is a G or K-type main-sequence star with a very large angular separation of 252 arcsec, corresponding to 9080 AU at the distance of HD 20782.[13] In 2011, two Neptune-mass planets were announced around the nearby HD 20781, and initially they too were believed to be in eccentric orbits, but less so.[14] However, later more detailed observations on this system revealed not only two more possible planets but also that all the planets in this system, in stark contrast to HD 20782, were likely in low eccentricity orbits.[15]

Planetary system

An extremely eccentric extrasolar planet was announced around HD 20782 in 2006.[16][17] In 2009 this planet's orbit was narrowed down, and it was found to have the highest eccentricity of all known exoplanets; this distinction has stood since 2012.

The HD 20782 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥1.49±0.11[15] MJ 1.3649+0.0466
−0.0495[15]		 597.065±0.043[18] 0.956±0.004[18] — —

See also

References

  1. 1 2 3 4 5 6 7 8 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.
  2. 1 2 3 Cousins, A. W. J.; Stoy, R. H. (1962). "Photoelectric magnitudes and colours of Southern stars". Royal Greenwich Observatory Bulletins. 64: 103. Bibcode:1962RGOB...64..103C. S2CID 118805499.
  3. 1 2 Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2 June 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. eISSN 1538-3881. ISSN 0004-6256. S2CID 250741593.
  4. 1 2 Valenti, Jeff A.; Fischer, Debra A. (July 2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500. eISSN 1538-4365. ISSN 0067-0049. S2CID 121398064.
  5. 1 2 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  6. 1 2 3 4 Ramírez, I.; Fish, J. R.; Lambert, D. L.; Allende Prieto, C. (13 August 2012). "Lithium Abundances in nearby FGK Dwarf and Subgiant Stars: Internal Destruction, Galactic Chemical Evolution, and Exoplanets". The Astrophysical Journal. 756 (1): 46. arXiv:1207.0499. Bibcode:2012ApJ...756...46R. doi:10.1088/0004-637X/756/1/46. eISSN 1538-4357. ISSN 0004-637X. S2CID 119199829.
  7. 1 2 van Belle, Gerard T.; von Braun, Kaspar (March 23, 2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". The Astrophysical Journal. American Astronomical Society. 694 (2): 1085–1098. arXiv:0901.1206. Bibcode:2009ApJ...694.1085V. doi:10.1088/0004-637x/694/2/1085. ISSN 0004-637X. S2CID 18370219.
  8. ↑ Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
  9. 1 2 3 4 Ghezzi, L.; Cunha, K.; Smith, V. V.; de Araújo, F. X.; Schuler, S. C.; de la Reza, R. (19 August 2010). "Stellar Parameters and Metallicities of Stars Hosting Jovian and Neptunian Mass Planets: A Possible Dependence of Planetary Mass on Metallicity". The Astrophysical Journal. 720 (2): 1290–1302. arXiv:1007.2681. Bibcode:2010ApJ...720.1290G. doi:10.1088/0004-637X/720/2/1290. eISSN 1538-4357. ISSN 0004-637X.
  10. 1 2 Gonzalez, G.; Carlson, M. K.; Tobin, R. W. (April 11, 2010). "Parent stars of extrasolar planets - X. Lithium abundances and v sin i revisited". Monthly Notices of the Royal Astronomical Society. Oxford University Press (OUP). 403 (3): 1368–1380. arXiv:0912.1621. Bibcode:2010MNRAS.403.1368G. doi:10.1111/j.1365-2966.2009.16195.x. ISSN 0035-8711. S2CID 118520284.
  11. ↑ "HD 20782". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-08-15.
  12. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711. S2CID 118879856.
  13. ↑ Desidera, S.; Barbieri, M. (October 24, 2006). "Properties of planets in binary systems". Astronomy & Astrophysics. EDP Sciences. 462 (1): 345–353. arXiv:astro-ph/0610623. Bibcode:2007A&A...462..345D. doi:10.1051/0004-6361:20066319. ISSN 0004-6361. S2CID 13813761.
  14. ↑ Mayor, M.; Marmier, M.; Lovis, C.; Udry, S.; Ségransan, D.; Pepe, F.; Benz, W.; Bertaux, J. L.; Bouchy, F.; Dumusque, G.; Curto, Lo; Mordasini, C.; Queloz, D.; Santos, N. C.; et al. (2011). "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets". arXiv:1109.2497 [astro-ph].
  15. 1 2 3 Udry, S.; Dumusque, X.; et al. (2019). "The HARPS search for southern extra-solar planets". Astronomy & Astrophysics. 622: A37. arXiv:1705.05153. Bibcode:2019A&A...622A..37U. doi:10.1051/0004-6361/201731173. ISSN 0004-6361. S2CID 119095511.
  16. ↑ Jones, Hugh R. A.; et al. (2006). "High-eccentricity planets from the Anglo-Australian Planet Search". Monthly Notices of the Royal Astronomical Society. 369 (1): 249–256. arXiv:astro-ph/0603335. Bibcode:2006MNRAS.369..249J. doi:10.1111/j.1365-2966.2006.10298.x.
  17. ↑ Schneider, J. "Notes for HD 20782". Extrasolar Planets Encyclopaedia. Archived from the original on July 2, 2007.
  18. 1 2 Kane, Stephen R.; et al. (2016). "Evidence for Reflected Light from the Most Eccentric Exoplanet Known". The Astrophysical Journal. 821 (1). 65. arXiv:1511.08679. Bibcode:2016ApJ...821...65K. doi:10.3847/0004-637X/821/1/65.
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