Observational properties of magneto-centrifugally launched protostellar jets

点击翻译按钮获取中文摘要

Star formation is one the the most active fields of astronomical research. Obviously, that a star can form is critical to our very existence and yet, from either a theoretical or observational point of view, how a star forms is still unclear. What we think we know is this. In a very large, diffuse gas cloud within a rotating galaxy, something triggers the gravitational collapse of a small region from which, through various stages of collapse, fragmentation, and further collapse, a so-called "protostar" is formed. A protostar is a spherical, gravitationally bound object still too diffuse and cold to sustain thermonuclear reactions---a huge, rapidly spinning Jupiter, if you will. Like figure skaters bringing in their arms to increase their spin, the spin of a collapsing protostar increases to the point where the centrifugal force matches gravity, and the final collapse to form a true star is stymied. Obviously, nature has found a way through this "centrifugal barrier"---stars are everywhere---and we believe this mechanism is to launch a "protostellar jet"; a long, narrow, supersonic stream of diffuse gas that carries away a small fraction of the protostellar mass but most of its angular momentum, and thus spin. Indeed, most astronomers believe that every protostar must launch a jet to allow its collapse to continue to form a true star where nuclear fusion can start. My area of research is, by way of computer simulation, to make the connection between what we know theoretically near the surface of a protostar at distances much less than the earth-sun distance, and what we can observe in the way of protostellar jets at scales many thousands of times greater. Our computer simulations are the first to bridge this gap, and what we are learning will help us understand what the large-scale observations can tell us about what is actually happening very close to the protostellar surface where, at least so far, no telescope can peer.