Fundamental Astronomy

Abstract

As the title suggests, this book is about fundamental things that one might expect to remain fairly the same. Yet astronomy has evolved enormously over the last few years, and only a few chapters of this book have been left unmodified. Cosmology has especially changed very rapidly from speculations to an exact empirical science and this process was happening when we were working with the previous edition. Therefore it is understand- able that many readers wanted us to expand the chapters on extragalactic and cosmological matters. We hope that the current edition is more in this direction. There are also many revisions and addi- tions to the chapters on the Milky Way, galaxies, and cosmology. While we were working on the new edition, the International Astronomical Union decided on a precise definition of a planet, which meant that the chapter on the solar system had to be completely restructured and partly rewritten. Over the last decade, many newexoplanets have also been discovered and this is one reason for the increasing interest in a newbranch of science – astrobiology, which now has its own new chapter. In addition, several other chapters contain smaller revisions and many of the previous images have been replaced with newer ones. Helsinki