o. How are planets detected around other stars?
Answer to (n):
The origin and formation of stars is not yet a perfectly understood subject and there are still competing theories on how what happened. However there is a piece of empirical evidence that is not theory-dependent and I think is clearly strong, although I suppose there may be other opinions.
This piece of evidence is provided by the Hertzsprung-Russell diagram of stars: A graph of the absolute magnitude of stars plotted against their surface temperature or color, used in the study of stellar evolution. Most of the better observed stars lie in certain areas of this diagram and the Sun is there as well.
Another strong piece of evidence is that of the chemical ...