WASP-19b is a hot Jupiter. These exoplanets, with masses similar to Jupiter, orbit much closer to their host stars than the largest planet in our solar system, turning the tranquil gasses of the planets into raging infernos. WASP-19b is so close to its parent star that it orbits in just 19 hours, atmospheric temperatures flare at 2000 degrees Celsius (3632 Fahrenheit), and astronomers just discovered the conditions are hot enough for something magnificent: there is titanium oxide in the atmosphere of WASP-19b.
The presence of such a heavy metal in the upper atmosphere of WASP-19b is a testament to how extreme the conditions on the planet really are. Titanium oxide is rare on Earth, found in minerals such as rutile, anatase, and brookite. It is also known to exist in the atmospheres of cool stars, but the detection of titanium oxide on WASP-19b—along with water and traces of sodium—is the first time the material has been found in a planet's atmosphere. The findings were published today in the journal Nature.
The discovery was made by an international team using the ESO's Very Large Telescope (VLT) in the Atacama Desert of Chile. Astronomers used the FORS2 instrument on the VLT, which allows them to analyze light passing through the atmosphere of an exoplanet when the planet moves in front of its host star. Spectroscopy can then be used to determine the composition of that planet's atmosphere, a method that has exciting implications when looking for biosignatures or signs of life on exoplanets.
"Detecting such molecules is, however, no simple feat," says Elyar Sedaghati, an ESO astronomer who contributed to the study. "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."
On WASP-1b, the titanium oxide works as a kind of heat sink, absorbing heat from the nearby star. It acts as insulation surrounding the outer atmosphere, blocking heat from the star and retaining temperatures within the planet. As a result, the upper atmosphere of the gas giant is hotter than the lower atmosphere, which is the opposite of a normal planet's heat distribution. The findings can help astronomers learn about the formation of different exoplanets throughout the galaxy.
"The presence of titanium oxide in the atmosphere of WASP-19b can have substantial effects on the atmospheric temperature structure and circulation." says Ryan MacDonald, a team member and astronomer at Cambridge University, United Kingdom.
The are plenty of hot Jupiters out there, being one of the most common types of exoplanets we have found. But WASP-19b is the only one we know of that blazes so hot, it has titanium floating around in the sky.