Thursday, August 27, 2009

WASP-18b, the Red Hot Planet of Doom

WASP-18b as visualized in Celestia.

When first discovered, "Hot Jupiters", giant exoplanets that orbited their stars more closely than Mercury orbits the Sun, were a source of amazement. 373 planets and 149 Hot Jupiters later close orbiting planets are a bit ho-hum.

Not so WASP-18b. Discovered by the Wide Angle Search for Planets, this amazing planet screams around its sun, HD 10069, in just under an Earth day. From WASP-18b's surface HD 10069 would occupy 30% of its sky (if you could see the sky from its surface). At over 7 times more dense than Jupiter, it probably has a large rocky core.

But it is so massive, and so close to its sun that WASP-18b that it should raise a tidal bulge on its sun, which should slow the planet down and make it spiral into its sun.

And there's the rub. WASP-18b should come close enough to HD 10069 to be torn apart in around 650,000 years. The likelihood that we would come across a planet so close to its death dive is quite remote, either we have been extraordinarily lucky in coming across WASP-18b, or there is something wrong with our theories of tidal dissipation in extrasolar systems. Either way, WASP-18b is a planet that will keep astronomers talking for some time.

Other discussions of WASP-18b at Sky and Telescope and ScienceNow!

If you want to add WASP-18b to Celestia, cut and paste the parameters below to a file and save it as WASP18b.ssc it the extras folder of Celestia, or download WASP18b.ssc to the extras folder.
=====================8<=cut===================================
"b" "HD 10069"

# WASP-18b Closest known exoplanet to star
# Detected via transit as well as radial velocity methods; from transit
# duration, inclination is 86 degrees, so mass can be determined.
# From transit dimming, radius is estimated at 1.11 jupiters.

{
Texture "exo-class4.*"
NightTexture "exo-class4night.*"

Color [0 0.36 1]
Albedo 0.05

Mass 3274 # M.sin(i) = 10.3 jupiters
Radius 79070

InfoURL "http://vo.obspm.fr/exoplanetes/encyclo/star.php?st=HD+10069"

EllipticalOrbit {
Period 0.0026
SemiMajorAxis 0.02026
Eccentricity 0.0092
Inclination 86
ArgOfPericenter -96
}

Obliquity 82 # guess, to match inclination
#EquatorAscendingNode 96 # guess, to match ascending node

# likely to be in captured synchronous rotation
}

AltSurface "limit of knowledge" "HD 10069/b"
{
Texture "extrasolar-lok.*"
}
=====================8<=cut=================================== The original paper is An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b, Nature, August 27, 2009, by Coel Hellier, D. R. Anderson, A. Collier Cameron, M. Gillon,4, L. Hebb, P. F. L. Maxted1, D. Queloz, B. Smalley, A. H. M. J. Triaud, R. G. West, D. M. Wilson, S. J. Bentley, B. Enoch, K. Horne, J. Irwin, T. A. Lister, M. Mayor, N. Parley, F. Pepe, D. L. Pollacco, D. Segransan, S. Udry & P. J. Wheatley

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