Lecture #16: A Star is Born
I. How long has the Sun been shining?
-- evidence from Earth: billions of years!
-- what got it so hot? (gravity)
-- what keeps it so hot? (nuclear energy)
-- why has it stayed so constant? (equilibrium, both energy and force)
II. What is a star?
-- nuclear forces
-- drop a nucleus to the core of the Sun: get fusion
-- why doesn't everything collapse and fuse?
III. Gravitational Collapse
-- gravity and collisions in particle clouds
-- the dance of gravity and pressure
-- the "virial theorem"
-- role of radiative cooling
-- analogy with orbits: how do you get an orbit to speed up continually?
IV. Hierarchy of scales
-- galaxies
-- star-forming associations
-- distribution of stellar masses: like cookie crumbs
-- cocoon nebula
-- binarity and multiple stars
-- planets