Using graphical and pictorial representations to teach introductory
  astronomy students about the detection of extrasolar planets via
  gravitational microlensing
  The detection and study of extrasolar planets is an exciting and thriving
field in modern astrophysics, and an increasingly popular topic in introductory
astronomy courses. One detection method relies on searching for stars whose
light has been gravitationally microlensed by an extrasolar planet. In order to
facilitate instructors' abilities to bring this interesting mix of general
relativity and extrasolar planet detection into the introductory astronomy
classroom, we have developed a new Lecture-Tutorial, "Detecting Exoplanets with
Gravitational Microlensing." In this paper, we describe how this new
Lecture-Tutorial's representations of astrophysical phenomena, which we
selected and created based on theoretically motivated considerations of their
pedagogical affordances, are used to help introductory astronomy students
develop more expert-like reasoning abilities.
