Analysis of data gathered by the Hubble and Spitzer space telescopes has revealed that the exoplanet WASP-18b, a hot Jupiter located about 325 light-years away from planet Earth, does not have water and has a stratosphere loaded with carbon monoxide. Exposure to too much carbon monoxide is potentially deadly for living organisms, including humans, on Earth.
Planetary Sunscreens Against Harmful Solar Radiations
On our home planet, ozone absorbs the UV in the stratosphere and protects Earth from most of the harmful radiation from the sun.
In a number of exoplanets with stratosphere, sunscreen-like molecules such as titanium oxide, a relative of the titanium dioxide commonly used as a sunscreen ingredients and a paint pigment on Earth, absorb the UV and visible radiation from the host star and release the energy as heat.
The new study hints that WASP-18b, which orbits close to its parent star, is characterized by composition unusual when compared to those of other worlds.
Based on the light emitted by the atmosphere of the exoplanet at infrared wavelengths, astronomers were able to detect the spectral fingerprints of water and other important molecules. The peculiar fingerprint of the heavyweight planet does not resemble any exoplanet that scientists have so far examined.
Overabundance Of Carbon Monoxide And Little Water Vapor
Extensive computer modeling revealed that there is an overabundance of carbon monoxide and there is little water vapor in the planet's atmosphere.
Two types of carbon monoxide signature namely an absorption signature at wavelength of about 1.6 micrometers and emission signature at about 4.5 micrometers showed that the stratosphere of WASP-18b has hot carbon monoxide and its troposphere, the layer of atmosphere below, contains cooler carbon monoxide.
It is the first time that researchers found both types of fingerprints in a single type of molecule presented in the atmosphere of an exoplanet.
"The derived composition and T/P profile suggest that WASP-18b is the first example of both a planet with a non-oxide driven thermal inversion and a planet with an atmospheric metallicity inconsistent with that predicted for Jupiter-mass planets at at ," the researchers wrote in their study published in The Astrophysical Journal Letters on Nov. 29.
Scientists said that the world may have formed quite different from Jupiter and other gas giants in other planetary systems.
"The composition of WASP-18b defies all expectations," said study researcher Kyle Sheppard, from NASA's Goddard Space Flight Center. "We don't know of any other extrasolar planet where carbon monoxide so completely dominates the upper atmosphere."
