Metal oxide discovered on exoplanet

A team of astronomers have discovered, for the first time, titanium oxide on the exoplanet WASP-19b.

Using the FORS2 spectrograph on the Very Large Telescope (VLT), the scientists were able to analyse the light passing through the exoplanet’s atmosphere as it passed in front of its mother star. They discovered that it contained small amounts of titanium oxide, water and traces of sodium alongside a strongly scattering global haze.

Elyar Sedaghati, a European Space Observatory fellow, said: “Detecting such molecules is, however, no simple feat. Not only do we need data of exceptional quality, but we also need to perform a sophisticated analysis. We used an algorithm that explores many millions of spectra spanning a wide range of chemical compositions, temperatures, and cloud or haze properties in order to draw our conclusions."

Hot Jupiter

WASP19b has approximately the same mass as Jupiter but is so close to its parent star that it completes an orbit in 19 hours with ­its atmosphere expected to reach almost 2000°C. Due to this, it is also referred as a ‘Hot Jupiter’. Titanium oxide is rarely seen on Earth but is known to exist in the atmosphere of cool stars. When in the atmosphere of planets such as WASP-19b, it acts as a heat absorber, similar to ozone.

If found in large enough quantities, titanium oxide molecules prevent heat from entering or escaping through the atmosphere, causing thermal inversion –temperatures being warmer in the higher atmosphere and vice versa. Ozone causes a similar effect in the Earth’s atmosphere, creating inversion in the stratosphere.

Ryan MacDonald, team member and astronomer at Cambridge University, said: “The presence of titanium oxide in the atmosphere of WASP-19b can have substantial effects on the atmospheric temperature structure and circulation.” Observations of the exoplanet were collected for more than a year, with different properties extrapolated through measuring its radius at different wavelengths.

Moving forward, this information will provide researchers with extra information to model exoplanet atmospheres. This could be of particular use in identifying habitable planets, once their atmospheres can be observed.