TOEFL Listening

🎧 Listening Transcript

Listen to part of a lecture in an astronomy class. The professor is discussing the concept of 'habitable zones' around stars. "Now, when we talk about habitable zones, we usually think of the region around a star where a planet could have liquid water on its surface. But as we've learned, this is a simplification. The concept assumes a planet with an Earth-like atmosphere, but in reality, many factors affect habitability. For example, a planet with a thick greenhouse atmosphere could keep water liquid even farther from its star. Conversely, a thin atmosphere might require the planet to be closer. Also, tidal heating, like that on Jupiter's moon Europa, can provide internal heat without starlight, potentially supporting subsurface oceans. So, while the classical habitable zone is a useful starting point, it's not the whole story. As we discover more exoplanets, we're finding worlds that challenge our assumptions. Some orbit red dwarf stars, which are cooler and dimmer than our sun, yet their habitable zones are much closer in. But red dwarfs are prone to flares that could strip atmospheres. So, we must consider stellar activity, not just distance. Clearly, defining habitability is complex and involves multiple variables."