A: Hey! Do you know how many planets there are in our solar system?

B: Sure. Eight planets

A: What are they?

B: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune

A: How about Pluto? Have you ever heard about it?

B: Yes, A while back, It was the ninth planet but it isn't counted as a planet any more

A: So what is Pluto?

B: It's a dwarf planet that lies in the Kuiper belt.

A: I still don't know much about this and I think I'll have to learn more about astronomy

B: Well, you should read astronomy books. It's so interesting!

Chúc bạn học tốt!!