What are the properties of stars on the Main Sequence? This lecture

discusses what happens to a star after it alights onto the Main

Sequence, burning H to He in its core, and maintaining a state

of Hydrostatic and Thermal Equilibrium. We will see how the mass

of a star determines its location along the Main Sequence and

influences its energy generation and internal structure. We finally

introduce the nuclear timescale and derive the Main-Sequence Lifetime

for stars, and discuss its consequences.

Recorded 2006 January 25 in 1008 Evans Laboratory on the Columbus campus

of The Ohio State University.