Galaxies that form stars intensely often blow out huge winds of gas, but exactly what launches them has been unclear. In a new arXiv preprint, astronomers used the XRISM space telescope's Resolve instrument (energy resolution of 4.5 eV) to study the prototypical starburst galaxy M82. They detected X-ray lines from FeXXV, ArXVII, and SXVI, allowing them to measure the hot gas temperature at 23 million degrees Kelvin, its mass at about 600,000 solar masses, and its line-of-sight velocity dispersion around 595 km/s. This is a detailed spectroscopic study of a single galaxy rather than a large sample; the velocity measurement has substantial uncertainty. The results show the hot gas is expanding fast enough to escape the galaxy and carries enough energy to drive cooler phases of the wind, meaning extra forces like cosmic rays aren't needed. About 60% of the energy from supernovae appears to heat this gas. This is a preprint and has not yet undergone peer review. Source: https://arxiv.org/abs/2603.24674