L2
讲座
1. What does the professor mainly discuss?
The idea that the orbits of some planets have changed over time
The theory that our solar system once contained more planets than it does now
Whether the gas-giant planets exert gravitational influence on one another
The origin of the material from which the gas-giant planets formed
2. Why does the professor discuss Earth’s Moon?
To help students envision the sizes of planetesimals and asteroids
To introduce the concept of planetary formation
To suggest that the planetary-migration hypothesis deserves serious consideration
To provide evidence that the planets in our solar system are no longer changing orbits
3. According to the planetary-migration hypothesis, what was responsible for the orbital shifts of the gas giants?
Collisions between the gas giants and their moons
Changes in the mass of gas giants as they passed through areas of dust and gas Gravitational interactions between Jupiter and the other gas giants
Gravitational interactions between the gas giants and small bodies of rock and ice
4. What difference between Jupiter and the other three gas giants does the professor emphasize?
Only Jupiter gained orbital energy.
Only Jupiter moved closer to the Sun.
Only Jupiter caused planetesimals to be ejected from the solar system.
Only Jupiter absorbed planetesimals into its core.
5. What did a computer simulation demonstrate?
Jupiter and Saturn are made of the same material of which asteroids are made.
The orbits of Jupiter and Saturn have shifted at least twice since the solar system formed.
A shift in the orbits of Jupiter and Saturn could help explain why the asteroid belt formed.
A shift in the orbits of Jupiter and Saturn could help explain why some areas of the asteroid belt are empty.
6. What point does the professor make when he discusses the existence of “hot
Jupiters” in other solar systems?（多选题）
Hot Jupiters have small orbits.
Hot Jupiters in other solar systems may have formed in our solar system.
Gas giants cannot form close to their sun.
The planet Mercury has moved closer to the Sun.
