Narrator: Listen to part of a lecture in an astronomy class.
Professor: Now, I want to talk about the discovery of exoplanets, specifically the first one found orbiting a sun-like star. That was 51 Pegasi b, discovered in 1995. Before that, astronomers had found planets around pulsars, but this was different. The big surprise was that 51 Pegasi b is a gas giant, similar to Jupiter, but it orbits extremely close to its star—closer than Mercury is to our Sun. This meant its orbital period is only about four days. According to the standard model of planet formation, gas giants should form far from their star, where it's cold enough for ice to condense. So finding a 'hot Jupiter' so close to its star challenged our understanding. Astronomers proposed that such planets might migrate inward over time, perhaps due to interactions with the protoplanetary disk. This discovery opened up a whole new class of planets and forced us to reconsider how planetary systems evolve.
❓ 题目 What is the main point the professor makes about the discovery of 51 Pegasi b?
A. It was the first exoplanet ever discovered.
B. Its close orbit to its star contradicted existing theories of planet formation.
C. It was found using a telescope more powerful than previous ones.
D. Its composition is similar to that of Mercury.
✅ 正确答案
Its close orbit to its star contradicted existing theories of planet formation.