ASTR 205 Astronomy Chapter 7

Which of the following relationships is the key to nuclear reactions in a star's core remaining under control? a. Luminosity depends on mass. b. Pressure depends on temperature. c. Density depends on mass. d. Weight depends on temperature. - b What is opacity? a. the balance between the pressure and force of gravity inside a star b. the force that binds protons and neutrons together to form a nucleus c. the temperature and density at which a gas will undergo thermonuclear fusion d. a measure of the resistance to the flow of radiation (photons) through a gas - d What causes the outward gas pressure that balances the inward pull of gravity in a main-sequence star? a. the rapid outward flow of gas b. the rapid inward flow of gas c. the high temperature and density of the gas d. the low mass of helium nuclei - c Why is convection important in stars? a. because it mixes the star's gases and increases the temperature of the star b. because it mixes the star's gases and transports energy outwards c. because it carries energy toward the core of the star d. because it carries the neutrinos to the surface of the star where they can escape - b How does the temperature inside a star determine how energy flows inside it? a. The radiation rate depends on temperature. b. The dependence of opacity on temperature makes convection happen. c. The dependence of opacity on temperature makes conduction happen. d. The temperature determines how much energy is produced at each layer. - b Which of the following is the best example of energy transport by conduction? a. Your feet are warmed when you hold them in front of a fire. b. Your feet are warmed when you wear socks. c. Your feet get cold when you stand on a cold floor. d. Your feet get cold when you hold them over a cool air vent. - c What does solving equations on a computer have to do with making a stellar model? a. The equations apply the laws of stellar structure at locations within the star. b. Equations can describe the H-R diagram and a star's location on it. c. The mass-luminosity equation tells you how to find a star's luminosity given its mass. d. Equations are used to model the nuclear reactions inside a star. - a What does the strong force do?a. It binds electrons to the nucleus in an atom. b. It holds the Moon in orbit around the Earth. c. It creates the magnetic field associated with sunspots. d. It binds protons and neutrons together to form a nucleus. - d