WASP-18b
 Size comparison of WASP-18b with Jupiter. | |
| Discovery | |
|---|---|
| Discovered by | Hellier et al. (SuperWASP)[1] |
| Discovery date | August 27, 2009[1] |
| Transit[1] (including secondary eclipses) | |
| Orbital characteristics | |
| Apastron | 0.02045 AU (3,059,000 km) |
| Periastron | 0.02007 AU (3,002,000 km) |
| 0.02026 ± 0.00068 AU (3,031,000 ± 102,000 km)[2] | |
| Eccentricity | 0.0092 ± 0.0028[2] |
| 0.94145455+0.00000087 −0.00000132[3] d 22.59487 h | |
| Inclination | 86 ± 2.5[2] |
| 96 ± 10[2] | |
| Star | WASP-18 |
| Physical characteristics | |
| 1.106+0.072 −0.054[2] RJ | |
| Mass | 10.3 ± 0.69[2] MJ |
| Temperature | 2500±200[4] |
WASP-18b is an extrasolar planet that is notable for having an orbital period of less than one day. It has a mass equal to 10 Jupiter masses,[1] just below the boundary line between planets and brown dwarfs, about 13 Jupiter masses. Due to tidal deceleration, it is expected to spiral towards and eventually merge with its host star, WASP-18, in less than a million years.[1] The planet is approximately 3.1 million kilometres (1.9 million miles) from its star, which is about 410 light-years from Earth. It was discovered by a team led by Coel Hellier, a professor of astrophysics at Keele University in England.[1]
Scientists at Keele and at the University of Maryland are working to understand whether the discovery of this planet so shortly before its expected demise (with less than 0.1% of its lifetime remaining) was fortuitous, or whether tidal dissipation by WASP-18 is actually much less efficient than astrophysicists typically assume.[1][5] Observations made over the next decade should yield a measurement of the rate at which WASP-18b's orbit is decaying.[6]
The closest example of a similar situation in the Solar System is Mars' moon Phobos. Phobos orbits Mars at a distance of only about 9,000 km (5,600 mi), 40 times closer than the Moon is to the Earth,[7] and is expected to be destroyed in about eleven million years.[8]
The study in 2012, utilizing a Rossiter–McLaughlin effect, have determined the planetary orbit is well aligned with the equatorial plane of the star, misalignment equal to 13±7°.[9]
2020 CHEOPS observation
In 2020 scientists used CHEOPS space telescope to observe WASP-189 b as it passed behind its host star (occultation) and measured the planet’s brightness and constrained its temperature to a scorching 3200 Celsius degrees. This makes WASP-189 b one of the hottest and most extreme planets, and entirely unlike any of the planets of the Solar System. At such temperatures, even metals such as iron melt and turn to gas, making the planet a clearly uninhabitable one.
Next, Cheops watched as WASP-189 b passed in front of its star (transit). WASP-189 b was found to be larger than thought at almost 1.6 times the radius of Jupiter. Scientists saw that the star itself is larger and cooler at its equator than at the poles, making the poles of the star appear brighter. Adding to this asymmetry is the fact that WASP-189 b’s orbit is inclined; it doesn’t travel around the equator, but passes close to the star’s poles.[11][12]
See also
References
- ^ a b c d e f g Hellier, Coel; et al. (2009). "An orbital period of 0.94days for the hot-Jupiter planet WASP-18b" (PDF). Nature. 460 (7259): 1098–1100. Bibcode:2009Natur.460.1098H. doi:10.1038/nature08245. PMID 19713926.
- ^ a b c d e f "Notes for planet WASP-18b". The Extrasolar Planets Encyclopaedia. Retrieved 2009-09-15.
- ^ McDonald, I.; Kerins, E. (2018). "Pre-discovery transits of the exoplanets WASP-18b and WASP-33b from Hipparcos". Monthly Notices of the Royal Astronomical Society: Letters. 477 (1): L21 – L24. arXiv:1803.06187. Bibcode:2018MNRAS.477L..21M. doi:10.1093/mnrasl/sly045.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Zhou, G.; Bayliss, D. D. R.; Kedziora-Chudczer, L.; Tinney, C. G.; Bailey, J.; Salter, G.; Rodriguez, J. (2015). "Secondary eclipse observations for seven hot-Jupiters from the Anglo-Australian Telescope". Monthly Notices of the Royal Astronomical Society. 454 (3): 3002–3019. arXiv:1509.04147. Bibcode:2015MNRAS.454.3002Z. doi:10.1093/mnras/stv2138.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Hamilton, Douglas P. (2009-08-27). "Extrasolar planets: Secrets that only tides will tell". Nature. 460 (7259). Nature Publishing Group: 1086–1087. Bibcode:2009Natur.460.1086H. doi:10.1038/4601086a. PMID 19713920.
- ^ Thompson, Andrea (2009-08-26). "Newfound Planet Might Be Near Death". Space.Com. Imaginova. Retrieved 2009-08-28.
- ^ Johnson, John Jr.; Astrophysicists puzzle over planet that's too close to its sun, Los Angeles Times (August 27, 2009).
- ^ Sharma, Bijay Kumar (2008-05-10). "Theoretical Formulation of the Phobos, moon of Mars, rate of altitudinal loss". arXiv:0805.1454 [astro-ph].
- ^ Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments, 2012, arXiv:1206.6105
- ^ Landau, Elizabeth; Zubritsky, Elizabeth (29 November 2017). "Exoplanet Has Smothering Stratosphere Without Water". NASA. Retrieved 29 November 2017.
- ^ "First results from Cheops: ESA's exoplanet observer reveals extreme alien world". esa.int. Esa. Retrieved 28 September 2020.
- ^ University of Bern (28 September 2020). "First study with CHEOPS data describes one of the most extreme planets in the universe". EurekAlert!. Retrieved 28 September 2020.
External links
Media related to WASP-18b at Wikimedia Commons
