TOEFL Listening

🎧 Listening Transcript

Listen to part of a lecture in an astronomy class. The professor is discussing the formation of planets. "Today, we're going to talk about how planets form, specifically around young stars. You might think that planets simply condense from the same cloud of gas and dust as the star, but it's more complex than that. The process begins with a rotating disk of gas and dust, known as the protoplanetary disk, surrounding a newborn star. Within this disk, tiny dust particles collide and stick together, gradually building up into larger bodies called planetesimals. Over millions of years, these planetesimals can merge through gravitational attraction to form protoplanets. However, not all disks are the same. The amount of heavy elements, like iron and silicon, plays a crucial role. Stars with more heavy elements tend to have more massive disks, which can lead to the formation of giant planets like Jupiter. In contrast, disks around stars with fewer heavy elements might only produce smaller, rocky planets. This explains why we see a variety of planetary systems in our galaxy, some with many large planets and others with none." Now, the professor discusses what factor is important in determining whether giant planets form.