Exam 11: Formation and Structure of Stars

Hydrostatic equilibrium is the balance between _____________ and radiation _____________.

When a large gas cloud starts to collapse in a free-fall due to gravity, the rotation rate will ______________.

During the main sequence lifetime of a star of any mass, the core of the star will be composed mainly of ____.

When a large gas cloud starts to collapse in a free-fall due to gravity, the temperature of the gas will _____________.

How do large mass stars in the upper region of the main sequence produce energy?

The proton-proton chain needs a high temperature because the protons must overcome the _____________.

Eighty percent of the stars on the H-R Diagram are on the main sequence, and that is because the star is in hydrostatic equilibrium due to the _____.

One of the major star forming regions in space is the Orion Nebula.

Pre-main sequence stars (not protostars) on the H-R Diagram are _____.

One of the factors that a large molecular cloud must overcome in order for gravitational contraction to begin is the thermal energy of the gas.

Hydrostatic equilibrium in a newborn star is regulated by a very unique thermostat called the _____________ thermostat.

There are several triggers that could start the gravitational contraction of a molecular cloud and subsequent star formation.  List two of these triggers.

Briefly describe the pressure-temperature thermostat in stars.

Energy flows by radiation or convection inside normal stars but almost never by _____________ because radiation or convection is much more efficient.

A protostar will continue to collapse due to gravity until it reaches the main sequence, and then gravitational collapse will stop when _____ begins.

Low mass stars like the Sun transport energy near their surface using convection.

Stellar winds and _____ will eventually blow away the protostellar disk and remnant cocoons of a protostar apart.

One of the factors that a large molecular cloud must overcome in order for gravitational contraction to begin is rotation of the gas cloud.

Before a giant molecular cloud can contract gravitationally, it must overcome four physical factors that resist compression.  What are these four factors?

Describe the concept of a "birth line" and identify where it falls on the H-R Diagram.