How stars form is one of the central unknowns of astrophysics. Star formation plays a crucial role in almost all aspects of astronomy from cosmology to planet formation. It is a complex process involving the collapse of molecular gas clouds from sizes of 1018cm to stars of 1011cm, with an accompanying increase in density of 21 orders of magnitude. There are three basic questions concerning star formation. What initiates it, what determines the resultant stellar properties and how do newly formed stars affect their natal environment?
We are addressing these questions via a combination of numerical simulations using both gravitational N-body and hydrodynamical codes, analytical investigations and comparisons with observations. Of particular interest are the dynamics involved when stars form in groups, from binary systems to clusters containing many thousands of stars. Simulations have shown that these dynamics have the potential to explain the variety of observed stellar properties. Current research includes investigating how the gravitational collapse and fragmentation of a molecular cloud is able to form whole groups of stars that, of necessity, interact during their formation. We are also studying the dynamics of the post-fragmented system, including stellar interactions and the dynamics between the stars and residual gas. Accretion of this gas is a strong candidate to explain the origin of the stellar mass spectrum.
The group is also using submillimetre observations to study how stars form, in particular whether the process is affected by magnetic fields. Small, iron-containing interstellar particles align themselves with the field and produce linearly-polarised emission, allowing us to map the magnetic field. The figure shows a newly forming cloud at the outer edge of an expanding supernova remnant. Simulations will show whether the field aids or hinders the collapse of cores to form stars.