HD 180902

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HD 180902
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 19h 19m 17.7078s[1]
Declination −23° 33′ 29.3632″[1]
Apparent magnitude (V) 7.78[2]
Characteristics
Spectral type K0 III/IV[3]
B−V color index +0.94[4]
Astrometry
Proper motion (μ) RA: 37.839±0.097[1] mas/yr
Dec.: −20.148±0.079[1] mas/yr
Parallax (π)9.5339 ± 0.0521[1] mas
Distance342 ± 2 ly
(104.9 ± 0.6 pc)
Absolute magnitude (MV)2.5 ± 0.3[4]
Orbit[5]
PrimaryHD 180902 A
CompanionHD 180902 B
Period (P)5880±440 d
Semi-major axis (a)7.15±0.69 AU
Eccentricity (e)0.335±0.025
Periastron epoch (T)2441100±1200 JD
Argument of periastron (ω)
(secondary)		73.3±1.6°
Semi-amplitude (K1)
(primary)		898±28 km/s
Details[4]
Mass1.52 ± 0.11 M☉
Radius4.1 ± 0.1 R☉
Luminosity9.4 ± 0.5 L☉
Temperature5030 ± 44 K
Metallicity [Fe/H]0.04 ± 0.03 dex
Age2.8 ± 0.7 Gyr years
Other designations
CD−23° 15276, HD 180902, HIP 94951[6]
Database references
SIMBADdata

HD 180902 is a binary star approximately 342 light years away in the constellation Sagittarius. The primary is a K-type star while the nature of the secondary is unknown since it has only been detected by its effect on the radial velocity of the primary.[5][1]

It has one confirmed planet, HD 180902 b,[4] and one candidate planet.[5]

Planetary system[]

HD 180902 b was discovered using the Doppler spectroscopy method with observations taken at the W. M. Keck Observatory.[4] The radial velocities showed there a long term linear trend in the data indicating an additional companion of unknown nature with a longer period.[4] This was later shown due to a stellar binary companion.[5]

There is second unconfirmed planet with a mass twice that of Neptune and an orbital period of 15 days.[5]

The HD 180902 planetary system[5]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥1.685±0.041 MJ 1.40±0.11 510.9±1.5 0.107±0.022 — —
c (candidate) ≥0.099±0.014 MJ 0.139±0.011 15.9058±0.0055 0.28±0.13 — —

References[]

  1. ^ a b c d e f 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.
  2. ^ Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  3. ^ Houk, N.; Smith-Moore, M. (1988). "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. 4. Bibcode:1988mcts.book.....H.
  4. ^ a b c d e f Johnson, John Asher; et al. (2010). "Retired a Stars and Their Companions. IV. Seven Jovian Exoplanets from Keck Observatory". Publications of the Astronomical Society of the Pacific. 122 (892): 701–711. arXiv:1003.3445. Bibcode:2010PASP..122..701J. doi:10.1086/653809.
  5. ^ a b c d e f Luhn, Jacob K.; et al. (2019). "Retired A Stars and Their Companions. VIII. 15 New Planetary Signals around Subgiants and Transit Parameters for California Planet Search Planets with Subgiant Hosts". The Astronomical Journal. 157 (4). 149. arXiv:1811.03043. Bibcode:2019AJ....157..149L. doi:10.3847/1538-3881/aaf5d0. S2CID 102486961.
  6. ^ "HD 180902". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-21.


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