WASP-18b

WASP-18b
Extrasolar planet List of extrasolar planets

Size comparison of WASP-18b with Jupiter.
Parent star
Star WASP-18
Constellation Phoenix[1]
Right ascension (α) 01h 37m 24.95s[1]
Declination (δ) -45° 40′ 40.8″[1]
Apparent magnitude (mV) 9.29[1]
Distance 330 ± 30 ly
(100 ± 10[2] pc)
Spectral type F9[2]
Mass (m) 1.25[3] M
Orbital elements
Semimajor axis (a) 0.02026 ± 0.00068[2] AU
Periastron (q) 0.02007 AU
Apastron (Q) 0.02045 AU
Eccentricity (e) 0.0092 ± 0.0028[2]
Orbital period (P) 0.94145299[1] d
    (22.59487 h)
Inclination (i) 86 ± 2.5[2]°
Argument of
periastron
(ω) 96 ± 10[2]°
Time of transit (Tt) 2454221.48163 ± 0.00038[2] JD
Physical characteristics
Minimum mass (m sin i) 10.3 ± 0.69[2] MJ
Radius (r) 1.106+0.072
−0.054
[2] RJ
Discovery information
Discovery date August 27, 2009[4]
Discoverer(s) Hellier et al. (SuperWASP)[4]
Detection method Transit[4]
Discovery status Published[4]
Other designations
HD 10069 b, HIP 7562 b
Database references
Extrasolar Planets
Encyclopaedia
data
SIMBAD data

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,[4] 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.[4] The planet is approximately 3.1 million kilometres (1.9 million miles) from its star, which is about 325 light years from Earth. It was discovered by Coel Hellier, a professor of astrophysics at Keele University in England.[5]

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.[4][6] Observations made over the next decade should yield a measurement of the rate at which WASP-18b's orbit is decaying.[7]

The closest example of a similar situation in our own 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 our moon is to the Earth,[8] and is expected to be destroyed in about eleven million years.[9]

See also

References

  1. ^ a b c d e "WASP-18b". Exoplanet Transit Database. http://var2.astro.cz/ETD/etd.php?STARNAME=WASP-18&PLANET=b. Retrieved 2009-08-29. 
  2. ^ a b c d e f g h i "Notes for planet WASP-18b". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/planet.php?p1=WASP-18&p2=b. Retrieved 2009-09-15. 
  3. ^ PlanetQuest: WASP-18 b
  4. ^ a b c d e f g Hellier, Coel; Anderson, D. R.; Cameron, A. Collier; Gillon, M.; Hebb, L.; Maxted, P. F. L.; Queloz, D.; Smalley, B.; Triaud, A. H. M. J.; West, R. G.; Wilson, D. M.; Bentley, S. J.; Enoch, B.; Horne, K. ; Irwin, J.; Lister, T. A.; Mayor, M.; Parley, N.; Pepe, F.; Pollacco, D. L.; Segransan, D.; Udry, S.; Wheatley, P. J. (2009-08-27). "An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b". Nature (Nature Publishing Group) 460 (7259): 1098–1100. Bibcode 2009Natur.460.1098H. doi:10.1038/nature08245. PMID 19713926. http://www.nature.com/nature/journal/v460/n7259/full/nature08245.html. Retrieved 2009-08-28. 
  5. ^ Suicidal planet seems on death spiral into star, breitbart.com, August 26, 2009
  6. ^ Hamilton, D. P. (2009-08-27). "Extrasolar planets: Secrets that only tides will tell". Nature (Nature Publishing Group) 460 (7259): 1086–1087. Bibcode 2009Natur.460.1086H. doi:10.1038/4601086a. PMID 19713920. http://www.nature.com/nature/journal/v460/n7259/full/4601086a.html. Retrieved 2009-08-28. 
  7. ^ Thompson, Andrea (2009-08-26). "Newfound Planet Might Be Near Death". Space.Com. Imaginova. http://www.space.com/scienceastronomy/090826-strange-planet.html. Retrieved 2009-08-28. 
  8. ^ Astrophysicists puzzle over planet that's too close to its sun, Los Angeles Times, August 27, 2009
  9. ^ Sharma, B. K. (2008-05-10). "Theoretical Formulation of the Phobos, moon of Mars, rate of altitudinal loss". arXiv:0805.1454 [astro-ph]. 

External links

Media related to [//commons.wikimedia.org/wiki/Category:WASP-18_b WASP-18b] at Wikimedia Commons

Coordinates: 01h 37m 25s, −45° 40′ 41″