Clues to hazy exoplanet complexity revealed in our own solar system
Data collected from observations recorded by NASA's Cassini mission has been used to propose ways to better understand the atmospheres of exoplanets. By studying the light of sunsets on Saturn’s satellite, Titan, scientists have shown how spectra are subtly altered when passing through a hazy atmosphere, thereby giving a greater insight into interpreting the spectral readings of the atmosphere of these distant worlds.
In spite of the fact that other planetary systems exist at mind-numbingly enormous distances from Earth, scientists still do manage to capture spectral readings (the study of light broken up into its component colors that indicates the composition of the gases it has passed through) of exoplanet atmospheres using a variety of techniques. One such way is when the exoplanet passes in front of the star around which it is orbiting. The light transiting through the atmosphere at that time is altered in specific, interpretable ways and after being observed by telescopes, is studied to determine the composition of that distant planet’s atmosphere.
This means that scientists can decipher such things as the planet’s gaseous composition, its temperature, and the way the atmosphere is structured.
Researchers from NASA's Ames Research Center in Moffett Field, California used the similarity between exoplanet transits and sunsets witnessed by the Cassini spacecraft at Titan to reveal just how intense the effects of hazes can be. Titan, blanketed by clouds and high-altitude hazes shows a variety of complex effects that scientists need to extricate to understand the composition of its atmosphere. Using data from Cassini's visual and infrared mapping spectrometer instrument taken from four observations of Titan made between 2006 and 2011, the research team provided analysis results that include the complex effects due to hazes, which can now be compared to exoplanet models and observations.
"Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets," said Tyler Robinson, a NASA Postdoctoral Research Fellow and the team’s leader, "So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini."
Using Titan as their model, Robinson and his team found that hazes high above some transiting exoplanets may limit what the spectra discloses to observers. As such, the observations may only be able to glean information from a planet's upper atmosphere which, on Titan, equates to about 90 to 190 miles (150 to 300 km) above the surface. The study also showed that the haze on Titan more strongly affects shorter wavelengths of light, which is contrary to the assumptions made when previously studying exoplanets.