HD 20782

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Star in the constellation Fornax

title: "HD 20782" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["fornax", "g-type-main-sequence-stars", "henry-draper-catalogue-objects", "hipparcos-objects", "planetary-systems-with-one-confirmed-planet", "multi-star-planetary-systems", "durchmusterung-objects"] description: "Star in the constellation Fornax" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/HD_20782" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Star in the constellation Fornax ::

| name = HD 20782 | epoch = J2000.0 | constell = Fornax | ra = | dec = | appmag_v = 7.38 | class = G1.5 V | b-v = +0.65 | radial_v = 40.7 | prop_mo_ra = +349.054 | prop_mo_dec = −65.305 | pm_footnote = | parallax = 27.8760 | p_error = 0.0172 | parallax_footnote = | absmag_v = +4.61 | mass = 0.96 | radius = 1.17 | luminosity = 1.262 | gravity = 4.35 | temperature = 5,741 | metal_fe = −0.06 | rotational_velocity = 3.0 | age_gyr = 8.5 | names = | Simbad = HD+20782 | NSTED = HD-20782 | EPE = HD+20782 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, 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, but it is receding with a heliocentric radial velocity of . At its current distance, HD 20782's brightness is diminished by 0.12 magnitudes due to interstellar extinction and it has an absolute magnitude of +4.61.

Properties

HD 20782 has a stellar classification of G1.5 V, indicating that it is an ordinary G-type main-sequence star like the Sun. It has also been given a cooler class of G3 V. It has 96% the mass of the Sun and 1.17 times the radius of the Sun. It radiates 1.262 times the luminosity of the Sun from its photosphere at an effective temperature of , 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, and it is estimated to be 8.5 billion years old, which is nearly twice of the Sun's age. It spins modestly with a projected rotational velocity of .

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. 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. However, later more detailed observations on this system revealed not only two more planets but also that all the planets in this system, in stark contrast to HD 20782, are likely in low eccentricity orbits. The binary star system has a total of five known planets around both stars.

Planetary system

An extremely eccentric extrasolar planet was announced around HD 20782 in 2006. 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.

| table_ref = | exoplanet = b | mass = ≥1.49 | period = 597.065 | semimajor = 1.3649 | eccentricity = 0.956 | inclination =

References

References

  1. Schneider, J. "Notes for HD 20782".
  2. {{Cite DR3. 5060104351007433472
  3. (2006). "High-eccentricity planets from the Anglo-Australian Planet Search". Monthly Notices of the Royal Astronomical Society.
  4. Desidera, S.. (October 24, 2006). "Properties of planets in binary systems". EDP Sciences.
  5. (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.
  6. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society.
  7. (2016). "Evidence for Reflected Light from the Most Eccentric Exoplanet Known". The Astrophysical Journal.
  8. (2011). "The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets".
  9. (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.
  10. (1962). "Photoelectric magnitudes and colours of Southern stars.". Royal Greenwich Observatory Bulletins.
  11. "HD 20782".
  12. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters.
  13. (9 September 2019). "The Revised ''TESS'' Input Catalog and Candidate Target List". The Astronomical Journal.
  14. van Belle, Gerard T.. (March 23, 2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars". American Astronomical Society.
  15. (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.
  16. (2019). "The HARPS search for southern extra-solar planets". Astronomy & Astrophysics.
  17. (13 August 2012). "Lithium Abundances in nearby FGK Dwarf and Subgiant Stars: Internal Destruction, Galactic Chemical Evolution, and Exoplanets". The Astrophysical Journal.
  18. Gonzalez, G.. (April 11, 2010). "Parent stars of extrasolar planets - X. Lithium abundances and ''v'' sin ''i'' revisited". Oxford University Press (OUP).

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fornaxg-type-main-sequence-starshenry-draper-catalogue-objectshipparcos-objectsplanetary-systems-with-one-confirmed-planetmulti-star-planetary-systemsdurchmusterung-objects