What fills the space between the stars? In addition to stars, planets, and dark matter, galaxies are home to vast reservoirs of gas and dust, high-energy particles, and magnetic fields. This is the interstellar medium (ISM): the stuff between the stars. The interstellar medium is the material from which new stars are born. It is actively sculpted by feedback from stellar winds, supernova explosions, and magnetic turbulence. KIPAC scientists study these and other processes to answer fundamental questions about the structure and evolution of our Galactic environment.

Magnetic fields are one of the most mysterious components of the interstellar environment. The Milky Way and galaxies like it host weak, large-scale magnetic fields. The magnetic field in the interstellar medium near the Sun is millions of times weaker than a refrigerator magnet, but even these weak magnetic fields can have a profound effect on interstellar physics. The interstellar magnetic field confines high-energy cosmic rays to the Galaxy, shapes the turbulent energy cascade, and plays a poorly understood role in the evolution of gas and the formation of stars. In addition, the very origins of cosmic magnetism and the structure of the Milky Way’s magnetic field are not well understood. KIPAC scientists are tackling this wealth of magnetic mysteries from many angles, using both observations and theory.

Astrophysicists probe magnetic fields by measuring the polarization of cosmic light. With multiwavelength observations and innovative data analysis techniques, KIPAC scientists unravel the effects of magnetic fields in interstellar environments. Polarized light from the Galaxy encodes information about magnetic fields in distant regions of space. Magnetically aligned dust grains emit polarized thermal radiation, allowing us to map magnetic fields in dusty interstellar clouds. Charged particles accelerated in the Galactic magnetic field emit synchrotron radiation that gives us another window onto magnetic fields in diffuse interstellar space. These signals are bright at microwave frequencies, meaning that sensitive experiments designed to map the polarized cosmic microwave background are also excellent probes of cosmic magnetism. KIPAC scientists collaborate on these cosmological experiments to take full advantage of their promise for Galactic science.