Download Chapter 18 Study Guide

Chapter 18 Study Guide ANSWERS
1. What does a refracting telescope use as its objective to gather and focus light?
A refracting telescope uses a lens as its objective.
2. What does a reflecting telescope use as its objective to gather and focus light?
A reflecting telescope uses a mirror as its objective.
3. What characteristics are used to classify stars?
Color, temperature, brightness, size and chemical composition.
4. What is the brightness of a star as seen from Earth called?
Apparent brightness.
5. What does the absolute brightness of a star depend on?
A star’s absolute brightness depends on the star’s size and temperature. Absolute brightness is
determined using the distance to a star and it’s apparent brightness.
6. What factor (variable) affects the color of a star?
Temperature of the star
7. What color are the coolest stars?
Red
8. What type of star has a high temperature but a low luminosity? (use H-R Diagram to determine)
White dwarf
9. What type of star has a low temperature but a high luminosity? (use H-R Diagram to determine)
Red supergiant
10. According to the Hertzsprung-Russell diagram, what relationship exist between the brightness
and temperature of a main sequence star?
The Hertzsprung- Russell diagram shows that main sequence stars increase in brightness as
they increase in temperature.
11. When is a star born?
A star is born when nuclear fusion begins within a protostar.
12. What variable determines whether a protostar becomes a star?
The protostar’s mass. If the protostar has enough mass there will be enough heat and pressure
to begin nuclear fusion.
13. What is a supernova?
A supernova is a large explosion that takes place at the end of massive star’s life cycle.