D - Astrophysics

Three Essential Ideas:

• One of the most difficult problems in astronomy is coming to terms with the vast distances between stars and galaxies and devising accurate methods for measuring them.

• A simple diagram that plots the luminosity versus the surface temperature of stars reveals unusually detailed patterns that help understand the inner workings of stars. Stars follow well-defined patterns from the moment they are created out of collapsing interstellar gas, to their lives on the main sequence and to their eventual death.

• The Hot Big Bang model is a theory that describes the origin and expansion of the universe and is supported by extensive experimental evidence.