The connection between Magnetic Fields and Star Formation

Hua-Bai Li

A galactic disc can fragment into spiral arms, which further break into
molecular clouds, the nursery of stars. Before the birth of stars,
protostellar discs develop from clouds. While the above process of star
formation is widely observed, it is still vigorously debated as to which
force regulates the fragmentation. The most mysterious candidate is
magnetic fields (B fields), owing much to the difficulties on both
observation and simulation grounds. Questions remain unanswered at every
stage of star formation. For example: Are B fields of galactic discs
strong enough to regulate cloud formation? Are cloud B fields dynamically
important for cloud core formation? How can protostellar discs develop
under the tension forces of cloud-core B fields (the so-called magnetic
braking catastrophe )? How can B fields influence star formation
efficiency?
I will present recent observations that can shed light on these
long-standing questions.