- Joleen Carlberg, jcarlberg@stsci.edu, http://www.stsci.edu/~jcarlberg/
- Project duration: 1 yr rotation project. (potential to expand to a thesis project)
- Project abstract: As stars evolve, many will inevitably engulf the innermost planets in their stellar systems. Many such engulfed planets will be destroyed within the star, polluting the stellar atmosphere. Whether such pollution can be detectable depends on the relative sizes of the engulfed planet to the stellar envelope and the degree to which the planet and stellar compositions differ. In our own solar system, the gas giants are sufficiently massive but chemically too similar to the Sun to create detectable changes. The terrestrial planets, in contrast, are chemically distinct from the solar abundance but lack sufficient total mass. One of the main results of the Kepler mission is the discovery of a large population of planets with masses intermediate to the terrestrials and gas/ice giants in our solar system. Over the last several years, intense characterization of these systems has begun placing constraints on these planet's likely compositions, including the atmospheric erosion timescales of close-in planets massive enough to have formed with H/He dominated atmospheres. Using these exoplanet results, the student will explore the potential pollution signatures of engulfing super-Earth/mini-Neptune planets over the relevant parameter space of the host stars' evolution to identify whether/how often there is a favorable chance of a pollution signature being detectable. The student will be encouraged to lead a paper on the result and to develop a graphical tool for visualizing the pollution signatures.
Figure from Sara Gettel et al 2016 ApJ 816 95. doi:10.3847/0004-637X/816/2/95, showing the masses and radii of super-Earth/sub-Neptune exoplanets and curves of varying compositions.
Below: The Earth's composition relative to the Sun, normalized to Fe ([X/Fe]) as a function of each element's condensation temperature. Volatile element's (low condensation temperature) are under abundant by as much as 1/100 ([X/Fe] = -2). For reference, points are color-coded by their nucleosynthetic origin.
