Impossible Planets

Discover Magazine, September, 1997

1. Some scientists claim that they have discovered planets orbiting other stars, but, as the article explains, they did not actually see these planets. What was the actual observation that these scientists made that led them to the conclusion that other solar systems exist?
2. Why does the existence of other solar systems, such as 51 Pegasi, upset the current scientific ideas of how our solar system formed?
3. All scientists don't agree with the conclusion that other solar systems exist. The article discusses at least two other possible interpretations of these observations. What are they, and why do some scientists propose them?
4. The term "theory" is very commonly misused, and it is misused in this article. How? The ideas about how solar systems form discussed in this article should actually be called what?
5. What do the scientists in the article say that they need in order to decide between different hypotheses of how planets form?