WASP-18b

Coordinates: Sky map 01h 37m 25s, −45° 40′ 41″
Source: Wikipedia, the free encyclopedia.
WASP-18b
SuperWASP)
Discovery dateAugust 27, 2009
Transit (including secondary eclipses)
Orbital characteristics[2]
0.02024 ± 0.00030 AU (3,028,000 ± 45,000 km)
Eccentricity0.0051+0.0070
−0.0037
0.94145223(24) d
22.59485352 h
Inclination83.5°+2.0°
−1.6°
−85°+72°
−96°
Semi-amplitude1814+23
−24 m/s
StarWASP-18
Physical characteristics[2]
Mean radius
1.240±0.079 RJ
Mass10.20±0.35 MJ
Mean density
6.6+1.2
−1.1 g/cm3
Temperature3,029±50 K (2,756 °C; 4,993 °F)[3]
2,781+25
−13 K (2,508 °C; 4,546 °F)[4]

WASP-18b is an exoplanet 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 toward and eventually merge with its host star, WASP-18, in less than a million years.[1] The planet is approximately 3.1 million km (1.9 million mi; 0.021 AU) from its star, which is about 400 light-years (120 parsecs) from Earth. A team led by Coel Hellier, a professor of astrophysics at Keele University in England, discovered the exoplanet in 2009.[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 planet's dayside temperature, as measured in 2020, is 3,029 ± 50 K (2,755.8 ± 50.0 °C; 4,992.5 ± 90.0 °F).[3] A 2023 study found an average dayside temperature of 2,781+25
−13 K (2,508 °C; 4,546 °F).[4]

A study in 2012, utilizing the Rossiter–McLaughlin effect, determined that the planetary orbit is well aligned with the equatorial plane of the star, with a misalignment equal to 13±7°.[9]

A 2017 study detected carbon monoxide in the planet's atmosphere, without signs of water vapor.[10][11] However, in 2023, the James Webb Space Telescope detected water vapor in the planet's atmosphere.[4][12]

Exoplanet WASP-18b − high carbon monoxide levels detected in stratosphere (artist concept)[11]

See also

  • SuperWASP

References

  1. ^
    S2CID 205217669
    .
  2. ^
    S2CID 241596186
    .
  3. ^
    S2CID 212717799
  4. ^
    PMID 37257843
    .
  5. S2CID 6247145
    .
  6. ^ Thompson, Andrea (2009-08-26). "Newfound Planet Might Be Near Death". Space.Com. Imaginova. Retrieved 2009-08-28.
  7. ^ Johnson, John Jr.; Astrophysicists puzzle over planet that's too close to its sun, Los Angeles Times (August 27, 2009).
  8. arXiv:0805.1454 [astro-ph
    ].
  9. S2CID 17174530
  10. doi:10.3847/2041-8213/aa9ae9
    .
  11. ^ a b Landau, Elizabeth; Zubritsky, Elizabeth (29 November 2017). "Exoplanet Has Smothering Stratosphere Without Water". NASA. Retrieved 29 November 2017.
  12. ^ "Webb telescope discovers traces of water in atmosphere of exoplanet with mass of 10 Jupiters". www.cbsnews.com. 2023-06-01. Retrieved 2023-06-12.

External links

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Media related to WASP-18b at Wikimedia Commons

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