Narrator: Listen to part of a lecture in an astronomy class. Professor: Now, let's talk about the asteroid belt, which lies between Mars and Jupiter. For a long time, astronomers thought it was the remnant of a planet that broke apart. But recent research suggests otherwise. The total mass of the belt is only about 4% of the Moon's mass. If a planet had formed there, it would have been much more massive. So why didn't it? The key factor is Jupiter's gravity. Jupiter's strong gravitational pull, especially early in the solar system's history, stirred up the material in that region. This prevented the particles from clumping together to form a planet. Instead, they remained as small bodies—asteroids. Also, the orbits of these asteroids are not uniform; some are quite elliptical. This is further evidence of Jupiter's influence, as it scattered them over time. So, the belt is not a failed planet's debris but rather a collection of planetesimals that never coalesced due to external perturbation.
❓ Pregunta What does the professor suggest about the asteroid belt?
A. A. It is the remains of a planet that exploded.
B. B. It contains enough mass to form a planet.
C. C. Jupiter's gravity prevented planet formation there.
D. D. The asteroids have perfectly circular orbits.
✅ Respuesta correcta
C. Jupiter's gravity prevented planet formation there.
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word