A supernova explosion creates an expanding bubble of hot gas which sweeps up the surrounding medium. Since the massive stars that become supernovae cannot drift far from their parent molecular clouds during their short lifetimes, the interaction of supernova remnants and molecular clouds should be a common occurrence. When a supernova remnant encounters a dense interstellar cloud, the compression may trigger gravitational collapse resulting in the formation of a new generation of stars. There is a great deal of interest in the regions of the interactions, especially where multi-wavelength observations can test theoretical models of shock waves within clouds. The expanding shock wave accelerates particles to high energies and may be responsible for the origin of Galactic cosmic ray particles. The interaction of supernova remnants and molecular clouds can be detected through intense stimulated emission in the 1720 MHz transition of the hydroxyl radical, OH. The maser (a microwave counterpart to laser) emission yields unique insights into the physical processes and conditions occurring during the interaction. Detailed modeling of the production and excitation of these species during the interaction will be used in this project led by Dr. Farhad Yusef-Zadeh to critically evaluate the theory of interstellar shock waves, the origin of supernova remnant masers, and the effect of X-rays emitted by the remnant on ionization and chemistry in the shocked gas. It will also enable the discovery of additional interactions between supernovae and interstellar clouds that will be crucial for future studies. The three-year program, which combines both theory and observations, will provide a crucial window into the physical and chemical processes occurring in shock waves induced within the cloud by the interaction.
The scientific aspects of this project will be closely related to education and public outreach components in three areas, each targeting a different audience. The goals of each outreach component are to help the public understand the process of scientific research, to communicate fundamental scientific concepts and to present the specific motivations and research results of this scientific program. Dr. Yusef-Zadeh has been working with programmers and educators to create and distribute learning-based problems to introduce the science topics of this project into undergraduate education at Northwestern and other universities. Dr. Yusef-Zadeh and colleagues have selected eight problems for a course to be offered as "Imaging in Astronomy". One of the problems will be using multi-wavelength observations of the W28 supernova remnant to discuss the physical and spatial relationships between X-ray, maser and synchrotron emitting gas. Building upon the strong relationship with the Adler Planetarium & Astronomy Museum in Chicago, a series of interactive educational products are being deployed to encourage the public understanding of research, as well as to present research results. Dr. Yusef-Zadeh will be working closely with educator and multimedia developers at Northwestern University to provide content and motivations needed for such activities. Dr. Yusef-Zadeh, educators, and undergraduate students at Northwestern are working on the second phase of a website (spaceimages.northwestern.edu). The space images website provides visitors with astronomy images and image manipulation tools along with necessary contextual information. ***
