The Interstellar Medium
Emily Petroff
The Milky Way galaxy in which we live is populated by hundreds of billions of stars, which make up most of the galactic mass; in between the stars, however, is a diffuse, complex network of matter, aptly named the interstellar medium (ISM). While only constituting about 15% of the observable galaxy by mass, the interstellar gas, primarily in the form of neutral, ionized and molecular hydrogen, and dust made of carbon and silicates, are essential to galactic structure. The gas regulates thermodynamic processes and maintains thermal equilibrium, and the dust mediates chemical reactions that, otherwise, would be impossible in space. The interstellar magnetic field, which is closely coupled to the gas, is also critical to maintaining hydrostatic equilibrium throughout the spiral of our Galaxy. All these components come together in the ISM to make its small- and large-scale effects some of the most important features in maintaining the structure of the Galaxy. In this talk, we will explore the physics behind these processes and how they all interact to produce the Milky Way Galaxy we see today.