The Protostars and Planets series for more than two decades has served the community with state of the art compilations of the current knowledge in the fields of star and planet formation. The previous volume PPV is published in 2007, but the contents is based on the year of the corresponding conference in 2005 in Hawaii. Since then, the field of protostars and planets has advanced tremendously, from a theoretical as well as observational point of view.
Regarding observational studies of star formation, the launch of the Herschel Space Observatory opened up a new window to investigate the peak of the spectral energy distribution of young star-forming regions, and SOFIA will continue exploring that wavelength regime. While previous investigations about the initial conditions of star formation often relied on more indirect approaches, we can now study the onset of star formation and the associated physical/chemical processes in unprecedented detail. Herschel also allows us to study main interstellar cooling lines like those of atomic carbon or oxygen as well as important molecular water lines. With these information at hand, we can analyze the fundamental cooling processes of the interstellar medium. The exoplanet searching and characterization has progressed enormously. More than 400 extra-solar planets have been detected, and thanks to the Kepler mission more and more super-earth like objects are among these planets. Having large samples is important for deriving statistical characteristics of exoplanets and exoplanetary systems, and since PPV the population synthesis models to explain these systems have also progressed dramatically. Furthermore, the field of transit spectroscopy rises to adulthood, and we start obtaining spectra from extrasolar planetary atmospheres. Therefore, the whole field of exoplanetary sciences changed from searching for new objects to really characterizing the physical and chemical properties of increasing samples. Also in our theoretical understanding of how planets form there has been tremendous progress since PPV. For instance, there has been a clear paradigm shift in how planetesimals are formed from cosmic dust: The new buzz words are “gravoturbulent planetesimal formation” and “particle growth in pressure traps”.
As for the planetary birth places: By the time PPVI will be held in 2013, the amount of observational data of protoplanetary disks has multiplied: large quantities of Spitzer data are already there and published, Herschel data are currently streaming in and the first results of the Atacama Large Millimeter Array (ALMA) are expected. Also our knowledge about the underlying disk physics e.g. the role of the turbulence driving mechanisms has revolutionized. We just want to mention the role of magnetic Prandtl and Reynolds numbers plus global simulations for MHD instabilities and the baroclinic instability for magnetically dead zones. Our better numerical simulations of disks in combination with radiation transport lead currently to a breakthrough in the migration problem of planets. What was a catastrophe in the past is now the remedy in population synthesis models to predict and explain the observed distributions of exoplanets and thus forms the ultimate tool to test the detailed physics in the various planet formation models. Our view of protoplanetary disks therefore is (and will be) incomparable in 2013 to what it was in 2005. Similarly, theoretical (in particular numeric) star formation research has made great advances since the last volume of the PP series. While in the past many theoretical studies were forced to focus on one or two aspects of star and planet formation only, it is now feasible to engage in a multi-scale and multi-physics approach to modeling the birth of stars and planets. The ever increasing computing power and the development of novel numerical algorithms allow us to study the evolutionary sequence from cloud formation, to star formation within these clouds with unprecedented precision and predictive power. It is now possible to combine 3-dimensional magnetohydrodynamic simulations with time-dependent chemistry and with radiative transfer calculations that allow for the self-consistent treatment of such diverse physical processes as molecular cloud formation in the turbulent multi-phase interstellar medium or studying the influence of ionizing feedback from the central high-mass star on the fragmentation and star-formation properties of the infalling envelope.