Kepler-18 is a star with a system of three exoplanets, positioned in the northern Constellation of Cygnus. It has an apparent visual magnitude of 14.0,[3] requiring a telescope to view. Based on parallax measurements, it is located at a distance of approximately 1,430 light-years (440 pc). It is drifting closer with a line of sight velocity component of −18.4 km/s.[4]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus[1] |
| Right ascension | 19h 52m 19.0688s[2] |
| Declination | +44° 44′ 46.808″[2] |
| Apparent magnitude (V) | 14.0[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | G7[citation needed] |
| Astrometry | |
| Radial velocity (Rv) | −18.40±0.02[4] km/s |
| Proper motion (μ) | RA: −1.436(14) mas/yr[2] Dec.: −20.341(14) mas/yr[2] |
| Parallax (π) | 2.2804±0.0168 mas[2] |
| Distance | 1,430 ± 10 ly (439 ± 3 pc) |
| Details[5] | |
| Mass | 0.972 ± 0.042 M☉ |
| Radius | 1.108 ± 0.051 R☉ |
| Luminosity | 0.93 L☉ |
| Surface gravity (log g) | 4.32 ± 0.12 cgs |
| Temperature | 5,383 ± 44 K |
| Metallicity [Fe/H] | 0.19 ± 0.06 dex |
| Rotational velocity (v sin i) | <4 km/s |
| Age | 10.0 ± 2.3 Gyr |
| Other designations | |
| KOI-137, KIC 8644288, 2MASS J19521906+4444467, Gaia DR2 2079295583282164992[6] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
This is an older star with an estimated age of around ten billion years. It has similar properties to the Sun with almost the same mass and a 10% larger radius. The star is radiating 93% of the Sun's luminosity from its photosphere at an effective temperature of 5,383 K.[5]
Planetary system
editThe star is orbited by 3 confirmed transiting planets, announced in 2011.[5] In 2021, it was found the orbital plane of Kepler-18d is slowly changing, likely under the gravitational influence of the additional giant planet.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination (°) |
Radius |
|---|---|---|---|---|---|---|
| b | 6.9 ± 3.4 M🜨 | 0.0447 ± 0.0006 | 3.504725 ± 0.000028 | — | 84.92 ± 0.26 | 2.00 ± 0.10 R🜨 |
| c | 17.3 ± 1.9 M🜨 | 0.0752 ± 0.0011 | 7.6415716 | — | 87.68 ± 0.22 | 5.49 ± 0.26 R🜨 |
| d | 16.4 ± 1.4 M🜨 | 0.1172 ± 0.0017 | 14.858941 | — | 88.07 ± 0.1 | 6.98 ± 0.33 R🜨 |
References
edit- ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
- 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- 1 2 Zacharias, N. (2012). The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). VizieR On-line Data Catalog. Vol. 1322. Bibcode:2012yCat.1322....0Z.
- 1 2 Jönsson, Henrik; et al. (August 17, 2020). "APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South". The Astronomical Journal. 160 (3). American Astronomical Society: 120. arXiv:2007.05537. Bibcode:2020AJ....160..120J. doi:10.3847/1538-3881/aba592. ISSN 0004-6256.
- 1 2 3 4 Cochran, William D.; et al. (2011). "Kepler 18-b, c, and d: A System Of Three Planets Confirmed by Transit Timing Variations, Lightcurve Validation, Spitzer Photometry and Radial Velocity Measurements". The Astrophysical Journal Supplement Series. 197 (1): 7. arXiv:1110.0820. Bibcode:2011ApJS..197....7C. doi:10.1088/0067-0049/197/1/7. S2CID 16505452.
- ↑ "Kepler-18". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 January 2018.
- ↑ Shahaf, Sahar; Mazeh, Tsevi; Zucker, Shay; Fabrycky, Daniel (2021), "Systematic search for long-term transit duration changes in Kepler transiting planets", Monthly Notices of the Royal Astronomical Society, 505 (1): 1293–1310, arXiv:2105.04318, Bibcode:2021MNRAS.505.1293S, doi:10.1093/mnras/stab1359
- ↑ Montet, Benjamin T.; Johnson, John Asher (2013), "Model-Independent Stellar and Planetary Masses from Multi-Transiting Exoplanetary Systems", The Astrophysical Journal, 762 (2): 112, arXiv:1211.4028v1, Bibcode:2013ApJ...762..112M, doi:10.1088/0004-637X/762/2/112, S2CID 29261765