Master's thesis defense by Daves Hoszowski – University of Copenhagen

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Master's thesis defense by Daves Hoszowski

Daves Tomasz Benedykt Hoszowski will defend his master's thesis Tuesday 3 December 2013 in the DARK lounge.

Title: Inflated Exoplanets

Supervisor: Assoc. Prof. Anja C. Andersen, Dark Cosmology Centre, NBI
Previous Supervisor: PDRA Lars Buchhave, NBI (currently at Harvard Smithsonian Center for Astrophysics)

Censor:  Assoc. Prof. Hans Kjeldsen, Astronomy Group, Aarhus University


Abstract

Planets vary in many physical properties, and those of exoplanets are quite unusual compared to the planets in our solar system. The Jovian planets, Jupiter and Saturn, have partially degenerate interiors which ensure that the planets have similar radii, but vary in mass. But similar radii are not observed for the Jovian-exoplanets, where the radii can vary by a factor of 2. This observation contradicts the models of the mass- radius relation and raises the question whether the models are faulty or a heating mechanism is in progress.

To answer the question, a description of the different detection techniques of exoplanets is made. This description tells us which method is required to investigate the exoplanets’ physical properties. Measurements of two systems from the Kepler Objects of Interest (KOI) are made to investigate if their radius is larger than expected, also known as inflated. But, it turns out that these exoplanets are not inflated, and can be explained by stellar irradiated exoplanet models. Therefore I have chosen a sample of 11 exoplanets, which all have a density below 0.2 g cm−3. The boundary is chosen to ensure that the exoplanets are inflated and that they are not following the mass-radii relation. The low-density exoplanets will be discussed on the base of three different heating mechanisms; enhanced atmosphere, tidal heating and ohmic dissipation.

Tidal heating is a viable solution, but not for all cases of inflated exo- planets. Ohmic heating could explain most events, but lacks evidence of its effect within the atmosphere. A detailed discussion of the low-density exoplanets illustrates the need of improving the data, and especially spec- tra, which can constrain parameters of the atmosphere.

A better understanding of inflated exoplanets could help astronomers understand how an irradiated envelope behaves. A greater understanding of the envelope will as well help physicists understand what happens to Hydrogen and Helium at high pressures, which are irreproducible on Earth.