Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Physics and Astronomy



First Advisor

Massimo Marengo


The abundance of discovered exoplanets show that our solar system may not be typical. We have several small rocky bodies close to our star, surrounded by large gaseous planets farther out, all on nearly circular orbits. In contrast, exoplanetary systems have been revealed to have extraordinary features: massive gas giants have been discovered both exceptionally close to their star (so-called ``hot Jupiters''), as well as much farther away than thought possible (hundreds to thousands of times farther than Earth is from the sun); the average exoplanet's orbit is not circular, but quite elliptical, with an eccentricity of 0.2. These features may be connected: it is possible that undiscovered far-separated giant planets could disrupt the orbits of inner planets. We performed direct imaging surveys of nearby stars using the Spitzer space telescope, making use of advanced point spread function subtraction techniques, to look for giant planets or brown dwarfs in the typical range of 10-100 projected AU (using IRAC's sub-array mode) and 100-1000 projected AU (using IRAC's full array). We found several infrared-color-selected potential companions around HD 76151, HR 8799, GJ 86, HD 160691, and GJ 581. These will require follow-up observations to test for common proper motion and confirmation of spectral type.

Copyright Owner

Alan Hulsebus



File Format


File Size

172 pages