Interstellar medium
The interstellar medium (ISM) is the gas, dust, magnetic fields, radiation, and cosmic rays that occupy the space between stars within a galaxy. In the Milky Way it exhibits multiple thermally and dynamically distinct phases spanning densities from less than 10⁻³ to more than 10⁶ particles per cm³ and temperatures from about 10 to over 10⁶ K. Its composition, structure, and energy balance regulate star formation and connect stellar feedback to galactic evolution.
