What is our solar system? Well, it's a simple question and, in a sense, it has a simple answer. Now, a solar system is the collection of objects that orbits around the sun, that orbit around our star.

What is our galaxy, the Milky Way, made of? Well, that is a really good question. I suppose the obvious answer, and it's right in part, is stars - some smaller than the sun and some bigger than the ...