1. What is the main purpose of the lecture?
A. To explain what happens when stars collide
B. To present new information about star formation
C. To propose a new theory about supernova explosions
D. To analyze the role of supernovae in galactic collisions
2. What do colliding galaxies and a supernova have in common? Click on 2 answers
A. Both events take place over billions of years
B. Both events result in the death of some stars.
C. Both events create clouds of excited hydrogen gas
D. Both events produce a similar type of radiation
3.How does the professor organize types of encounters between galaxies?
A. From the quickest encounters to the slowest
B. From the most distant encounters to those closest to Earth
C. From the most frequent types of encounters to the least frequent
D.From the most violent types of encounters to the least violent
4. Why are astronomers uncertain as to which of two unnamed galaxies collided with the Cartwheel Galaxy?
A. Each shows evidence typical of a galactic collision
B. Computer simulations show that either one is a possibility
C. Neither one has a bright ring showing the presence of new stars.
D. Both galaxies are at an equal distance from the Cartwheel Galaxy
5. Why do astronomers believe that the Milky Way galaxy is interacting with another nearby galaxy?
A. Star formation has increased in both galaxies.
B. The two galaxies are slowly moving toward each other
C. A stream of gas and dust connects the two galaxies
D. The Hubble Space Telescope found high levels of hydrogen gas near the two galaxies
6. What is the professor’s opinion of recent observations of the Antennae galaxies?
A. It is too early to know if they will produce important findings
B. They are of limited value, as they only capture one stage in a long process
C. They illustrate the professor s point that there are multiple forms of galaxy encounters.
D. They are consistent with a commonly accepted scientific theory
答案：B CD D A C D