The space between the stars in the Milky Way and all other galaxies is full of dust and gas, the raw materials from which stars and planets are made.
But the dynamics of these galactic mosh pits, which are perhaps best known through the spectacular images from the Hubble Space Telescope of towering nebulas caught in the act of churning out stars, are still mysterious. Now, an international team of scientists, including two from the University of Wisconsin–Madison, has clocked the turbulence of the warm ionized gas in interstellar space, a measurement that promises a better handle on a process responsible for regulating the appearance and composition of the Milky Way.
"All the stars with their planetary systems are born out of the interstellar medium," explains UW-Madison astronomy professor Alexander Lazarian who, with graduate student Blakesley Burkhart, contributed the theoretical foundation of the new study. "The interstellar medium is a multiphase system with complex interactions between molecular clouds, diffuse gas of different temperatures and densities, as well as magnetic fields penetrating and critically affecting all the phases."
Understanding the dynamics of the interstellar medium is important, Lazarian asserts, because it is responsible for the one essential process of all galaxies: star formation. But turbulence in the interstellar medium has only attracted the interest of astrophysicists in the last decade thanks to advances in both theory and observation. New measurements using a variety of techniques, in addition to images from telescopes such as Hubble, have helped create a new portrait of the interstellar medium, revealing highly irregular dust and gas features moving at supersonic speeds.
But describing the complex swirl of the interstellar medium and inferring its properties is extremely difficult. Complicating the picture is the presence of powerful interstellar magnetic fields that influence the ebb and flow of interstellar dust and gas. The Nature study, says Burkhart, provides a new measure of that magnetic turbulence.