These is for the reader who wants more information on the
subject of a given chapter, both more elementary and more extensive.
Some of the references are to journal or popular articles, and will
therefore change as new material becomes available. That is
why this material was not included in the text for this edition.
In the News
One of the great things about studying astronomy, as opposed
to classical physics, for example, is that the field is always being
shaped by new discoveries. With new telescopes across the electromagnetic
spectrum, we are really in the golden age of astronomy. As important
discoveries are announced, we will note them here, in the context
of material already in the book. In the conceptual spirit of the
book, we will look at these discoveries with an eye of what they tell
us about how some astronomical object works. This is still to come.