Chapter 18

What do the orbits of planets and satellites tell us about the rotation of the cloud that formed the solar system?

Why are radio and infrared radiation more useful than visible light in studying molecular clouds?

Describe the structure of a giant molecular cloud.

What evidence do we have that stars form in the cores of giant molecular clouds?

Suppose there were no magnetic fields in interstellar space. What effect might this have on the number of young stars in the galaxy?

What halts the collapse of a protostar?

Where in an H-R diagram are young stars located when they first become observable using visible light? Why aren't they visible at an earlier stage of their careers?

What is the relationship between Herbig-Haro objects and jets of gas from young stars?

Describe the steps in the process through which microscopic solid grains accumulated to form objects a few thousand kilometers in diameter.

What evidence do we have that the planets formed as a result of collisions of planetesimals?

What evidence do we have that the final stage of the formation of the solar system consisted of collisions between planet-sized objects?