Over the past three decades, scientists have discovered over 5,000 planets outside our solar system. Among these exoplanets, one intriguing type is the lava world, a super-Earth characterized by scorching temperatures and oceans of liquid lava. Mantas Zilinskas, a Ph.D. student, has made significant contributions to this field by developing models that simulate potential atmospheres of these alien worlds. These simulations offer valuable guidance to astronomers who are using the James Webb Space Telescope to search for these exotic atmospheres. Zilinskas is set to receive his Ph.D. on Wednesday, May 24.
Unlike the familiar eight planets in our solar system, most exoplanets observed so far display unique characteristics. Examples include hot Jupiters, gas giants situated closer to their parent star than Mercury is to the Sun, and rostral lava worlds, larger than Earth, with orbits so close to their parent star that their surfaces are covered in flowing lava oceans.
Our knowledge about these distant worlds remains limited, as Zilinskas points out. Astronomers can estimate certain features such as mass, radius, and distance from the parent star, but this information alone does not provide a complete picture. To gain further insights into exoplanet atmospheres, astronomers employ a technique called spectroscopy. By analyzing the light from the parent star that passes through an exoplanet’s atmosphere and reaches Earth, scientists can identify the unique colors of light absorbed by different molecules and atoms present in the atmosphere. This creates a distinctive fingerprint for each exoplanet, enabling researchers to determine the composition of its atmosphere.
However, extracting properties from spectroscopic observations is a challenging task. That’s why theoretical astrophysicists like Zilinskas develop mathematical models that predict how certain properties translate into observable data. “I calculate what astronomers might observe,” Zilinskas explains. “The purpose of my simulations is to inform astronomers about what to look for and what these observations can reveal about exoplanets.”
Zilinskas has dedicated his Ph.D. research to studying the atmospheres of lava worlds and their potential observation using the James Webb Space Telescope, which was launched in late 2021. “Although we have not yet detected these atmospheres, we believe they exist. Gases rich in silicate can evaporate from lava oceans, forming a thin and tenuous atmosphere,” Zilinskas explains. “Through our models, we aim to predict the chemical composition and key properties of these atmospheres, such as temperature variations, and assess their impact on the observed light spectrum.”
To achieve this, Zilinskas employed one-dimensional models, which assume that the most significant chemical changes in the atmosphere occur vertically rather than horizontally. These models calculate the chemical conditions at various points within the atmosphere. Zilinskas combined this approach with radiative transfer models that determine how light from the parent star traverses the atmosphere and how its spectrum changes during the process.
“Although two- and three-dimensional models exist, they require substantial time and computational power,” Zilinskas notes. “Moreover, since our understanding of lava worlds is limited, employing the faster and more versatile one-dimensional models allows us to explore a wide range of potential atmospheric compositions.”
Through his simulations, Zilinskas demonstrated that the James Webb Space Telescope has the capability to observe the atmospheres of lava worlds if they indeed exist. He also emphasized the significant leap forward that this space telescope represents in the field. Currently, the telescope continues to observe exoplanets, including lava worlds. Zilinskas expresses his hope that his Ph.D. research will serve as a valuable guide for future observations of lava world atmospheres.
Source: Leiden University