Astronomy:WASP-18
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Phoenix[1] |
| Right ascension | 01h 37m 25.03328s[2] |
| Declination | −45° 40′ 40.3747″[2] |
| Apparent magnitude (V) | 9.273[3] |
| Characteristics | |
| Spectral type | F6IV/V[4] + M6.5V[5] |
| Astrometry | |
| Radial velocity (Rv) | 3.47±0.34[2] km/s |
| Proper motion (μ) | RA: 25.404(10)[2] mas/yr Dec.: 20.479(11)[2] mas/yr |
| Parallax (π) | 8.1443 ± 0.0116[2] mas |
| Distance | 400.5 ± 0.6 ly (122.8 ± 0.2 pc) |
| Details[6] | |
| Mass | 1.294+0.063 −0.061 M☉ |
| Radius | 1.319+0.061 −0.062 R☉ |
| Luminosity | 2.68+0.28 −0.26 L☉ |
| Surface gravity (log g) | 4.310+0.036 −0.033 cgs |
| Temperature | 6432±48 K |
| Metallicity [Fe/H] | 0.107±0.080 dex |
| Rotational velocity (v sin i) | 11.9±1.2[7] km/s |
| Age | 1.57+1.4 −0.94 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | A |
| B | |
| Exoplanet Archive | data |
| Extrasolar Planets Encyclopaedia | data |
WASP-18 is a magnitude 9 star located 400 light-years (120 parsecs) away in the Phoenix constellation of the southern hemisphere.[1] It has a mass of 1.29 solar masses.[6]
The star, although similar to the Sun in terms of overall contents of heavy elements, is depleted in carbon. The carbon to oxygen molar ratio of 0.23±0.05 for WASP-18 is well below the solar ratio of 0.55.[9]
There is a red dwarf companion star at a separation of 3,519 AU.[5]
Planetary system
In 2009, the SuperWASP project announced the discovery of a large, hot Jupiter type exoplanet, WASP-18b, orbiting very close to this star. It has an orbital period of less than a day and a mass 10 times that of Jupiter.[4]
Observations from the Chandra X-ray Observatory failed to find any X-rays coming from WASP-18,[10] and it is thought that this is caused by WASP-18b disrupting the star's magnetic field by causing a reduction in convection in the star's atmosphere. Tidal forces from the planet may also explain the higher amounts of lithium measured in earlier optical studies of WASP-18.[11]
A 2019 study proposed a second candidate planet with a 2-day orbital period based on transit-timing variations,[12] but a 2020 study using data from both TESS and ground-based surveys ruled out the existence of a planet with the proposed properties, setting an upper limit of 10 Earth masses on any planet with this period.[6]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 10.20±0.35 MJ | 0.02024+0.00029 −0.00031 |
0.94145223(24) | 0.0051+0.0070 −0.0037 |
83.5+2.0 −1.6° |
1.240±0.079 RJ |
See also
- SuperWASP
- List of exoplanets
References
- ↑ 1.0 1.1 "WASP-18b". Exoplanet Transit Database. http://var2.astro.cz/ETD/etd.php?STARNAME=WASP-18&PLANET=b.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ Maxted, P. F. L. et al. (2011). "UBV(RI)C photometry of transiting planet hosting stars". Monthly Notices of the Royal Astronomical Society 418 (2): 1039–1042. doi:10.1111/j.1365-2966.2011.19554.x. Bibcode: 2011MNRAS.418.1039M.
- ↑ 4.0 4.1 Hellier, Coel et al. (2009). "An orbital period of 0.94days for the hot-Jupiter planet WASP-18b". Nature 460 (7259): 1098–1100. doi:10.1038/nature08245. PMID 19713926. Bibcode: 2009Natur.460.1098H. http://orbi.ulg.ac.be/bitstream/2268/28276/1/nature08245.pdf.
- ↑ 5.0 5.1 Csizmadia, Sz.; Hellard, H.; Smith, A. M. S. (March 2019). "An estimate of the k2 Love number of WASP-18Ab from its radial velocity measurements". Astronomy & Astrophysics 623: A45. doi:10.1051/0004-6361/201834376. Bibcode: 2019A&A...623A..45C.
- ↑ 6.0 6.1 6.2 6.3 Cortés-Zuleta, Pía et al. (April 2020). "TraMoS. V. Updated ephemeris and multi-epoch monitoring of the hot Jupiters WASP-18Ab, WASP-19b, and WASP-77Ab". Astronomy & Astrophysics 636: A98. doi:10.1051/0004-6361/201936279. Bibcode: 2020A&A...636A..98C.
- ↑ Torres, Guillermo et al. (2012). "Improved Spectroscopic Parameters for Transiting Planet Hosts". The Astrophysical Journal 757 (2): 161. doi:10.1088/0004-637X/757/2/161. Bibcode: 2012ApJ...757..161T.
- ↑ "WASP-18". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=WASP-18.
- ↑ Polanski, Alex S.; Crossfield, Ian J. M.; Howard, Andrew W.; Isaacson, Howard; Rice, Malena (2022), "Chemical Abundances for 25 JWST Exoplanet Host Stars with KeckSpec", Research Notes of the American Astronomical Society 6 (8): 155, doi:10.3847/2515-5172/ac8676, Bibcode: 2022RNAAS...6..155P
- ↑ Pillitteri, I. (July 2014). "No X-rays from WASP-18. Implications for its age, activity, and the influence of its massive hot Jupiter". Astronomy & Astrophysics 567: A128. doi:10.1051/0004-6361/201423579. Bibcode: 2014A&A...567A.128P. https://www.aanda.org/articles/aa/abs/2014/07/aa23579-14/aa23579-14.html.
- ↑ "NASA's Chandra X-ray Observatory Finds Planet That Makes Star Act Deceptively Old". http://chandra.harvard.edu/press/14_releases/press_091614.html.
- ↑ Pearson, Kyle A. (December 2019). "A Search for Multiplanet Systems with TESS Using a Bayesian N-body Retrieval and Machine Learning". The Astronomical Journal 158 (6): 243. doi:10.3847/1538-3881/ab4e1c. Bibcode: 2019AJ....158..243P.
Coordinates: 
01h 37m 25s, −45° 40′ 41″
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