Astronomers Directly Measure M82's Extreme Galactic Wind

Scientists using the XRISM X-ray telescope directly measured the hot wind from the starburst galaxy M82, finding speeds over 3 million km/h and temperatures near 25 million °C. The hot wind can drive about four solar masses of gas per year outward, contributing to a 40,000‑light‑year plume, while a total of seven solar masses per year are moving outward—with about three solar masses unaccounted for—raising questions about where that gas goes and how galactic winds affect galaxy evolution. Cosmic rays may contribute but aren’t the primary engine according to current data.