Grant: Discovery Grants Program - Individual

The universe is filled with spherical objects: stars and planets are familiar examples. However, the universe also contains a wide variety of flattened, disk-like objects. Common examples are "accretion" disks in which a central object grows in mass by accreting gas from the disk. The protostellar disks surrounding newly forming stars are examples, and it is in such disks that new planets form. The physics of accretion disks is very complex and only partially understood. Better understanding of the physics of disks in general would lead to better understanding of the formation of stars, planets, and galaxies -- ie. the "building blocks" of our universe. This Discovery Grant Proposal focuses on a novel type of disk known as a "decretion" disk in which gas is flowing outward from a central star. Many of the same physical processes that operate in accretion disks operate here. Such decretion disks have been detected surrounding hot, massive stars known as Be stars. These stars are valuable "laboratories" for the detailed study of disks because they are nearby and relatively bright and a wide range of astronomical observations can be made. For example, light from the disk can be spread into its component colours to form a spectrum. Another newly emerging type of observation combines the light from two or more telescopes to allow direct images of the disks to be made for the first time. This Discovery Grant Proposal continues a research program into the construction of computer models for the decretion disks surrounding Be stars. These complex models can be used to interpret both types of observations mentioned. Valuable information can then be extracted about the fundamental physical processes that operate in such disks.