Scientists have made a groundbreaking discovery about the galaxy M82, which forms stars at an astonishing rate—ten times faster than our Milky Way. They have measured the speed of the hot gas erupting from its center, clocking it at over 3 million kilometers per hour. This fast-moving gas creates a massive outflow that stretches tens of thousands of light-years into space.
The XRISM spacecraft, a collaboration between JAXA and NASA, made this revelation using its highly sensitive instrument to capture X-ray emissions from superheated iron in M82. Published in Nature, this study helps answer a long-standing question: what fuels the dramatic outflows visible streaming from this nearby galaxy?
M82 is known as a starburst galaxy. It consumes gas at a rapid rate, leading to powerful winds and enormous outflows. Understanding how these winds work is crucial for grasping how galaxies evolve and how they influence star formation.
The measurement of the hot gas relied on a principle called the Doppler effect. This is the same phenomenon that alters the pitch of a passing ambulance siren. In M82, the gases are moving in all directions, broadening their spectral signature. The research team, led by Erin Boettcher from the University of Maryland, found that this broadening indicated an incredible wind speed. The gas’s temperature reached about 45 million degrees Fahrenheit (25 million degrees Celsius), reinforcing theories about the pressure created within galaxy cores.
For decades, astronomers believed that shockwaves from supernovae and intense star formation could heat surrounding gas and kick-start these winds. However, before XRISM, no instrument could measure velocities detailed enough to test this theory. The new findings confirm this idea broadly, revealing that the hot wind can expel about four solar masses of gas annually from M82’s core.
Yet, the full story remains unclear. The gas expelled is enough to form seven solar masses of stars each year, but only four of those are accounted for by the hot wind. What happens to the remaining three solar masses? Do they escape the galaxy? Or do they recirculate back? No one knows yet.
This mystery highlights the need for future research. XRISM has turned vague theories into specific questions that must be addressed by upcoming missions. As astronomer Edmund Hodges-Kluck notes, this discrepancy is crucial and prompts further investigation.
The implications of understanding M82’s outflows extend beyond just this galaxy. They can shed light on the life cycles of galaxies and play a part in cosmic evolution. As we continue to explore the universe, discoveries like these will deepen our understanding of how galaxies, including our own, shape and change over time.
For more details on this research, you can visit NASA’s XRISM mission page.
