| Extrasolar planet detection methods have recently advanced to the point where planets only slightly larger than the Earth, both in mass and size, are detectable with currently available instruments. The newly discovered class of planets known as "super-Earths" with masses in the range 1-10 M ⊕ afford scientists the ability to study planets and planet formation scenarios in a mass regime that does not exist in our solar system. This thesis describes work aimed at both detecting and characterizing these low-mass planets.;If a transiting planet is found to vary in its measured orbital period over a series of transits, the resulting transit timing variations (TTVs) may be due to the gravitational pull of an additional planet in the system. The first part of this thesis (Chapters 2-4) describes some of the first efforts to use the TTV method to detect low-mass planets in known transiting systems. In Chapters 2 and 3 we present transit timing measurements for both the HD 209458 and HD 189733 systems, using data from the Canadian MOST space telescope. We additionally study the effects of HID 189733's large surface star spots on measuring accurate transit times in Chapter 4. While we find no evidence of low-mass companion planets in either of these transiting hot Jupiter systems, the null results from our TTV analyses serve to provide strong constraints on planet formation theories.;Characterization of super-Earth atmospheres will be possible with future instruments, such as those aboard the James Webb Space Telescope. However, the interpretation of any such observations will necessitate direct comparison against theoretical atmosphere models. To this end, we have developed a planetary atmosphere model specifically for the study of super-Earths, and we present this model and some of its applications in Chapters 5-7. In Chapter 5 we determine how to best constrain the atmospheric hydrogen content of a super-Earth atmosphere through observations of the planetary emission and transmission spectrum. In Chapter 6 we turn our attention to the problem of direct detection of low-mass planets with next generation ELTs. We conclude this thesis in Chapter 7, where we describe the recent addition of a self-consistent temperature correction routine to the model atmosphere. |
