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HD 20003
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Hydrus
Right ascension	03h 07m 37.91875s
Declination	−72° 19′ 18.8010″
Apparent magnitude (V)	8.39
Characteristics
Spectral type	G8 V
B−V color index	0.771±0.015
Astrometry
Radial velocity (Rv)	−16.174±0.0005 km/s
Proper motion (μ)	RA: +71.893 mas/yr ; Dec.: −7.995 mas/yr
Parallax (π)	23.8764 ± 0.0283 mas
Distance	136.6 ± 0.2 ly ; (41.88 ± 0.05 pc)
Absolute magnitude (MV)	5.18
Details
Mass	0.942±0.046 M☉
Radius	0.92+0.05; −0.01 R☉
Luminosity	0.705+0.002; −0.001 L☉
Surface gravity (log g)	4.423±0.323 cgs
Temperature	5494±27 K
Metallicity [Fe/H]	+0.04±0.02 dex
Rotation	38.9±4 d
Rotational velocity (v sin i)	2.216±0.273 km/s
Age	5.3+2.8; −2.6 Gyr
Other designations
	CD−72°148, HD 20003, HIP 14530, SAO 255959, 2MASS J21281220-2143340
Database references
SIMBAD	data
Exoplanet Archive	data

HD 20003 is a star in the southern constellation Hydrus. With an apparent visual magnitude of 8.39,^[2] this yellow-hued star is much too faint to be visible to the naked eye. It is located at a distance of 136.6 light years from the Sun based on parallax. HD 20003 is drifting closer with a radial velocity of −16 km/s,^[1] and is predicted to come to within 97 light-years in around 1.4 million years from now.^[2]

This object is an ordinary, G-type main-sequence star with a stellar classification of G8 V.^[3] It is around five^[4] billion years old with a magnetic activity cycle lasting about ten years^[7] and a projected rotational velocity of 2.2 km/s.^[4] The star has 94%^[4] of the mass of the Sun and 92%^[1] of the Sun's radius. The metallicity of this star is similar to the Sun, if slightly higher.^[2] It is radiating 70.5% of the luminosity of the Sun from its photosphere at an effective temperature of 5,510 K.^[1]

The survey in 2015 have ruled out the existence of any stellar companions at projected distances above 18 astronomical units.^[8]

Planetary system

HD 20003 has two planets that are at least 12 and 13.4 times as massive as the Earth and have orbital periods of just under 12 and 34 days, respectively. These were detected by the HARPS survey in 2011,^[9] and the findings were confirmed using Spitzer in 2017.^[7]

Since 2017, a third planet HD 20003 d on roughly half-year orbit is suspected.^[5]

The HD 20003 planetary system^[9]
Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥0.0378±0.0031 $M$ _J	0.0974±0.0016	11.849±0.0028	0.4±0.08	—	—
c	≥0.0422±0.004 $M$ _J	0.1961±0.0032	33.823±0.0654	0.16±0.09	—	—

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c ^d ^e ^f Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
^ ^a ^b Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
^ ^a ^b ^c ^d ^e ^f ^g Soto, M. G.; Jenkins, J. S. (July 2018), "Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars (SPECIES). I. Code description and dwarf stars catalogue", Astronomy & Astrophysics, 615: 28, arXiv:1801.09698, Bibcode:2018A&A...615A..76S, doi:10.1051/0004-6361/201731533, S2CID 119107228, A76.
^ ^a ^b ^c ^d Udry, S.; Dumusque, X.; Lovis, C.; Ségransan, D.; Diaz, R. F.; Benz, W.; Bouchy, F.; Coffinet, A.; Lo Curto, G.; Mayor, M.; Mordasini, C.; Motalebi, F.; Pepe, F.; Queloz, D.; Santos, N. C.; Wyttenbach, A.; Alonso, R.; Collier Cameron, A.; Deleuil, M.; Figueira, P.; Gillon, M.; Moutou, C.; Pollacco, D.; Pompei, E. (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
^ "HD 20003". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-12-20.
^ ^a ^b Gillon, M.; et al. (May 2017), "The Spitzer search for the transits of HARPS low-mass planets. II. Null results for 19 planets", Astronomy & Astrophysics, 601: 23, arXiv:1701.01303, Bibcode:2017A&A...601A.117G, doi:10.1051/0004-6361/201629270, S2CID 86862862, A117.
^ Mugrauer, M.; Ginski, C. (12 May 2015). "High-contrast imaging search for stellar and substellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 450 (3): 3127–3136. Bibcode:2015MNRAS.450.3127M. doi:10.1093/mnras/stv771. hdl:1887/49340. Retrieved 19 June 2020.
^ ^a ^b Mayor, M.; 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.EP].

[GaiaDR2-1] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.

[Anderson2012-2] ^ ^a ^b ^c ^d ^e ^f Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.

[Houk1979-3] Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.

[Soto2018-4] ^ ^a ^b ^c ^d ^e ^f ^g Soto, M. G.; Jenkins, J. S. (July 2018), "Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars (SPECIES). I. Code description and dwarf stars catalogue", Astronomy & Astrophysics, 615: 28, arXiv:1801.09698, Bibcode:2018A&A...615A..76S, doi:10.1051/0004-6361/201731533, S2CID 119107228, A76.

[Udry2017-5] Udry, S.; Dumusque, X.; Lovis, C.; Ségransan, D.; Diaz, R. F.; Benz, W.; Bouchy, F.; Coffinet, A.; Lo Curto, G.; Mayor, M.; Mordasini, C.; Motalebi, F.; Pepe, F.; Queloz, D.; Santos, N. C.; Wyttenbach, A.; Alonso, R.; Collier Cameron, A.; Deleuil, M.; Figueira, P.; Gillon, M.; Moutou, C.; Pollacco, D.; Pompei, E. (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

[SIMBAD-6] "HD 20003". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-12-20.

[Gillon2017-7] Gillon, M.; et al. (May 2017), "The Spitzer search for the transits of HARPS low-mass planets. II. Null results for 19 planets", Astronomy & Astrophysics, 601: 23, arXiv:1701.01303, Bibcode:2017A&A...601A.117G, doi:10.1051/0004-6361/201629270, S2CID 86862862, A117.

[8] Mugrauer, M.; Ginski, C. (12 May 2015). "High-contrast imaging search for stellar and substellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 450 (3): 3127–3136. Bibcode:2015MNRAS.450.3127M. doi:10.1093/mnras/stv771. hdl:1887/49340. Retrieved 19 June 2020.

[Mayor2011-9] Mayor, M.; 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.EP].

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