For going on two decades, Scientific American's "Ask the Experts" column has been answering reader questions on all fields of science. We've taken your questions from the basic to the esoteric and reached out to top scientists, professors, and researchers to find out why the sky is blue or whether we really only use 10 percent of our brains.

Now, we've combed through our archives and have compiled some of the most interesting questions (and answers) into a series of books. Organized by subject, each title provides short, easily digestible answers to questions on that particular branch of the sciences.

The second title in our series--Astronomy--looks skyward and explains a variety of universal phenomena and theories. Are you curious about how planets acquire rings or what creates those gorgeous spiral arms around galaxies? Or maybe you want to know why the Big Bang didn't collapse into a black hole. Astrophysicists, professors, and scientists tackle questions about stars, planets, asteroids, galaxies, and nebulae, the expanding universe as well as the oddities--black holes, wormholes, and dark matter.

Listen in and find out what we know--and what we don't know--about these wonders.