HD 181720

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HD 181720
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 19h 22m 52.99s[1]
Declination –32° 55′ 08.6″[1]
Apparent magnitude (V) 7.84[2]
Characteristics
Spectral type G1V[2]
Apparent magnitude (B) 8.44
Apparent magnitude (J) 6.652
Apparent magnitude (H) 6.346
Apparent magnitude (K) 6.294
V−R color index 0.599[2]
Astrometry
Radial velocity (Rv)-45.404 km/s
Proper motion (μ) RA: 88.154 mas/yr
Dec.: -415.038 mas/yr
Parallax (π)16.5816 ± 0.0664[3] mas
Distance196.7 ± 0.8 ly
(60.3 ± 0.2 pc)
Absolute magnitude (MV)4.10[2]
Details
Mass0.92[2] M☉
Radius1.39[2] R☉
Luminosity1.94[2] L☉
Surface gravity (log g)4.24 ± 0.15[2] cgs
Temperature5781 ± 18[2] K
Metallicity-0.53 ± 0.02[2]
Rotation47 days
Rotational velocity (v sin i)1.5[2] km/s
Other designations
CD–33°14164, GCRV 69331, HIP 95262, LTT 7666, NLTT 47718, PPM 298918, SAO 211218, 2MASS J19225298-3255079, Gaia DR2 6745589980571162752
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

HD 181720 is an 8th-magnitude G-type main sequence star located approximately 190 light-years away in the constellation Sagittarius. This star is larger, hotter, brighter and less massive than our Sun. Also its metal content is three-tenths as much as the Sun.

The star HD 181720 is named Sika. The name was selected in the NameExoWorlds campaign by Ghana, during the 100th anniversary of the IAU. Sika means gold in the Ewe language.[4][5]

Planetary system[]

In 2009, a gas giant planet was found in orbit around the star. It was named "Toge" in 2019. The planets around such metal-poor stars are rare (only two known similar cases are HD 111232 and HD 22781).[6]

The HD 181720 planetary system[2][7]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b (Toge) ≥0.37 MJ 1.78 956 ± 14 0.26 ± 0.06 — —

See also[]

References[]

  1. ^ a b van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. ^ a b c d e f g h i j k l Santos, Nuno C.; Mayor, Michel; Benz, Willy; Bouchy, François; et al. (2010). "The HARPS Search for Southern Extra-solar Planets XXI. Three New Giant Planets Orbiting the Metal-poor Stars HD 5388, HD 181720, and HD 190984". Astronomy and Astrophysics. 512 (A47): A47. arXiv:0912.3216. Bibcode:2010A&A...512A..47S. doi:10.1051/0004-6361/200913489. S2CID 118675798.
  3. ^ 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.
  4. ^ "Approved names". NameExoworlds. Retrieved 2020-01-02.
  5. ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2020-01-02.
  6. ^ Adibekyan, Vardan (2019), "Heavy Metal Rules. I. Exoplanet Incidence and Metallicity", Geosciences, 9 (3): 105, arXiv:1902.04493, Bibcode:2019Geosc...9..105A, doi:10.3390/geosciences9030105, S2CID 119089419
  7. ^ Santos, Nuno C.; Mayor, Michel; Bonfils, Xavier; Dumusque, Xavier; Bouchy, François; Figueira, Pedro; Lovis, Christophe; Melo, Claudio; Pepe, Francesco; Queloz, Didier; Ségransan, Damien; Sousa, Sérgio Gonçalves; Udry, Stéphane (2011), "The HARPS search for southern extrasolar planets XXV. Results from the metal-poor sample", Astronomy and Astrophysics, 526: A112, arXiv:1011.2094, Bibcode:2011A&A...526A.112S, doi:10.1051/0004-6361/201015494, S2CID 119106340

Coordinates: Sky map 19h 22m 52.9859s, −32° 55′ 08.595″

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