Description

An understanding of how stars form is of central importance to many areas of astronomy, ranging from searches for planets to observations of the distant universe. Theoretical work on star formation at Yale has concentrated on several major aspects of the problem, including the fragmentation of collapsing gas clouds, the role of disks in star formation, the origin of binary and multiple systems, and the formation of star clusters. A central issue in this subject has been the need to understand the factors that determine stellar masses and the stellar Initial Mass Function (IMF). Observational studies have shown that stars have a characteristic mass similar to the mass of the Sun, which may be understandable theoretically in terms of the expected mass scale for cloud fragmentation. However, the IMF also has a long tail extending to much higher masses, and the formation of massive stars and the origin of the upper IMF are not yet well understood; this is one of the present frontier areas of research on star formation.

A topic of great current interest is star formation in the very early universe, which may soon become observable at high redshifts. Theoretical arguments suggest that early star formation might have favored massive stars, and these stars would have been important sources of energy and heavy elements for the early universe. Recent work at Yale has modeled numerically the formation of the first stars from primordial gas uncontaminated with heavy elements, which had not yet been created by stellar nucleosynthesis. These calculations predict a mass scale for cloud fragmentation that is much larger that the mass of the Sun, and this suggests that the first stars were indeed very massive and would have had important effects on the early universe and on galaxy formation. Future instruments may be able to observe systems of such stars directly at high redshifts, providing a link between star formation studies and research on cosmology and galaxy formation.

More information and lists of relevant publications can be found here.