Read the story about the search for planets far out in our solar system. You can also listen to the story by clicking the audio link at the top of the article.
With a partner, answer the following text-dependent questions.
- According to the article, what is planet X?
- Why don’t we already know all of the planets in our solar system?
- What new technologies are being used to look for new planets?
- What specific evidence makes scientists think there are probably large objects beyond Pluto?