Cypress College ASTR 116 Homework
Astronomy 116, Homework CHAPTER 11 (A) The Interstellar Medium, Birth
of Stars. Due:
Print Last, First Name and date on the small Scantron in INK. Print
your last name in BIG BLOCK letters on the back of the Scantron.
Use a No. 2 pencil to fill out Scantron. Read the chapter.
Look at the videos and simulations in the CD-ROM. Answer all True/False and
Fill in the Blank questions. Then answer the following questions and
turn in your Scantron only. Choose the best answer.
1. Which two ingredients are needed to make an emission nebula?
- a) Interstellar gas and dust.
- b) Cool stars and interstellar dust.
- c) Hot stars and interstellar gas.
- d) Cool stars and interstellar gas.
2. Most stars probably formed:
- a) Alone.
- b) In clusters.
- c) From constellations.
- d) In the nucleus of the Galaxy.
3. Evidence for star formation theory comes from:
- a) Tracking one star through time.
- b) Plotting stars on the Hertzsprung-Russell diagram.
- c) Studying different objects at different stages of evolution and
piecing together an evolutionary picture.
- d) Emission nebulae, exclusively.
4. What makes the subject of star formation so difficult and complex?
- a) Star formation is too expensive to study in detail.
- b) Clouds, fragments, protostars, stars, and nebulae all interact
and influence each other.
- c) Shock waves disrupt the orderly evolution of stars.
- d) Stars live too long to be observed from birth to death.
5. What is characteristic of a main sequence star?
- a) Rapid rotation and a strong stellar wind.
- b) Nuclear fusion in the core varies according to the amount of
gravitational contraction that occurs.
- c) The rate of nuclear energy generated in the core equals the rate
of energy radiated from the surface.
- d) all of the above
- e) none of the above
6. What is the key factor that determines the temperature, density, radius,
luminosity, and pace of evolution of a prestellar object?
- a) Rotation.
- b) Magnetism.
- c) Mass.
- d) Heat.
7. A cloud fragment too small to form a star becomes:
- a) A black hole.
- b) A brown dwarf.
- c) A T Tauri star.
- d) Nothing, it simply dissipates.
8. Which event marks the birth of a star?
- a) Fusion of hydrogen atoms into helium atoms.
- b) Collapse of an interstellar cloud.
- c) Formation of a photosphere.
- d) Instability in an interstellar cloud.
9. If the initial interstellar cloud in star formation has a mass sufficient
to form hundreds of stars, how does a single star form from it?
- a) One star forms at its center and blows the rest of the matter
back into space.
- b) One star forms and the rest of the matter goes into making planets,
moons, and other objects of a solar system.
- c) The cloud fragments into smaller clouds and forms many stars
at one time.
- d) The cloud is disrupted by its own rotation so that it reduces
its mass down to that of a typical star.
10. At what stage of evolution do T Tauri stars occur?
- a) Just as the collapsing cloud becomes luminous.
- b) Just prior to the protostar stage.
- c) When a protostar is on the verge of becoming a main sequence
star.
- d) After the star has established itself as a main sequence star.