On, In, and About Interstellar Superbubbles and Supershells
The structure and dynamics of the diffuse interstellar medium are dominated by large cavities blown up by stellar winds and supernovae, which arise from massive stars. Massive stars have short lifetimes, are born in clusters, and die before the clusters dissipate, so the multiple stars blow the bubbles, which can get very large. We recognize them from their hot interiors and dense shells, which consist of gas swept up by the shock fronts. The shells are visible in the 21-line, the H-alpha line, synchrotron emission, and--amazingly--in Faraday rotation, the details of which reveal complex plasma dynamical processes. The Sun lives within an old cavity, which was originally recognized by diffuse X-ray emission from its interior hot gas and known as the 'Local Hot Bubble'; however much--maybe all--of its purported X-ray emission actually comes from the Earth's heliopause! The Local Bubble's interior is mainly empty except for low-pressure ionized wisps and a high-pressure, extremely cold sheet oof neutral gas.
Time: Jun. 22, 2015, 2:30 pm
Venue: A601, NAOC