  We describe a new inquiry design aimed at teaching advanced high-school to
senior college students the basics of stellar populations. The inquiry is
designed to have students come up with their own version of the
Hertzsprung-Russell diagram as a tool to understand how stars evolve based on
their color, mass, and luminosity. The inquiry makes use of pictures and
spectra of stars, which the students analyze and interpret to answer the
questions they come up with at the beginning. The students undergo a similar
experience to real astronomers, using the same tools and methods to figure out
the phenomena they are trying to understand. Specifically, they use images and
spectra of stars, and organize the data via tables and plots to find trends
that will then enable them to answer their questions. The inquiry also includes
a "thinking tool" to help connect the trends students observe to the larger
picture of stellar evolution. We include a description of the goals of the
inquiry, the activity description, the motivations and thoughts that went into
the design of the inquiry, and reflections on how the inquiry activity worked
in practice.
