HD 180902
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]
| 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 |
| Distance | 342 ± 2 ly (104.9 ± 0.6 pc) |
| Absolute magnitude (MV) | 2.5 ± 0.3[4] |
| Orbit[5] | |
| Primary | HD 180902 A |
| Companion | HD 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] | |
| Mass | 1.52 ± 0.11 M☉ |
| Radius | 4.1 ± 0.1 R☉ |
| Luminosity | 9.4 ± 0.5 L☉ |
| Temperature | 5030 ± 44 K |
| Metallicity [Fe/H] | 0.04 ± 0.03 dex |
| Age | 2.8 ± 0.7 Gyr years |
| Other designations | |
| Database references | |
| SIMBAD | data |
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]
| 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
- 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.
- 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.
- 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.
- 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.
- 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.
- "HD 180902". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-21.