Investigation 5: Variable X-ray Sources

Overview: Youth discover and investigate why we sometimes see objects which appear to change their flux over time. They examine terrestrial and visible light astronomical objects, before learning how to investigate flux variability in X-ray emitting objects.

Instructors guide students through a simple analysis and interpretation of one X-ray source, 4U1822. They investigate how some of the properties they've already learned to measure may change during different parts of a source's light curve. These act as clues to what kind of object this source might be. (angular/linear size, variability, color) As a way to practice making arguments and connecting models of objects with observations about them, students take each observation of the investigated object in turn (i.e. start with just limits on size, then add in levels of flux variability, then color information) and try to rule out possible models. Students then debate as a class as to which model makes the best sense for this object and try to convince a majority of their peers of which model is most "reasonable".