Titanium discovered in exoplanet’s atmosphere

The discovery of metallic oxides in the planet’s atmosphere has changed how we’ll examine alien worlds in the future


Artist’s impression of the exoplanet WASP-19b, which is 815 light years away from Earth. Image credit: ESO/M. Kornmesser

Astronomers have detected titanium oxide in an exoplanet atmosphere for the first time ever. Using the European Southern Observatory’s (ESO) Very Large Telescope and the FORS2 instrument, astronomers were able to examine the atmosphere of the hot-Jupiter planet, WASP-19b, to detect the rare molecule. This analysis of the atmosphere revealed the chemical composition, temperature and pressure structure of the unusual exoplanet, which lies 815 light years away.

Elyar Sedaghati, a recent Technical University of Berlin graduate, led the team of astronomers as they inspected the atmosphere of the exoplanet WASP-19b with the best possible detail. The astonishing exoplanet is about 30 per cent more massive than Jupiter, and because of its extremely close proximity to the parent star, it completes one orbit every nineteen hours.

When WASP-19b passes in front of its parent star, starlight reflects off the planet’s atmosphere, sending subdued clues of its composition to us on Earth. Using the FORS2 instrument, these astronomers were able to decipher that the atmosphere has a temperature of around 2000 degrees Celsius (3600 degrees Fahrenheit), and it also contains water, traces of sodium and more importantly, titanium oxide.

As WASP-19b passes in front of it’s parent star, the starlight interacts with the planet’s atmosphere, and sends subtle clues that eventually reach Earth. Image credit: ESO/ M. Kornmesser

“Detecting such molecules is, however, no simple feat,” explains Sedaghati. “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.”

Titanium oxide is rarely seen on Earth, but it is known to exist in the atmospheres of cool stars. When this molecule exists in large quantities in an exoplanet’s atmosphere, it prevents heat from entering or escaping, leading to thermal inversion. Thermal inversion is when the temperature is increased at higher altitudes, and then decreases lower down, opposite to what we understand here on Earth.

By discovering the presence of metal oxides, such as titanium oxide, astronomers can now make improved models for exoplanet atmospheres. This will play an important role in determining the habitability of worlds beyond our Solar System.

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