For the first time, scientists have measured the incredible speed of hot gas erupting from the heart of M82, a galaxy that forms stars at a rate ten times faster than the Milky Way. This gas is moving at speeds exceeding 3 million kilometres per hour, capable of creating a massive outflow that extends tens of thousands of light-years into space.
This significant discovery arose from the XRISM spacecraft, a joint project by JAXA and NASA. The highly sensitive Resolve instrument onboard detected X-ray emissions from superheated iron in M82’s core. These findings, published in Nature on March 25, address a question that has puzzled astronomers for decades: what drives the dramatic outflow seen from this nearby galaxy?
Starburst galaxies, like M82, are intriguing to researchers due to their intense activity. They consume gas reserves rapidly, creating powerful winds and enormous outflows. Understanding these phenomena is essential for grasping how galaxies evolve and how star formation operates within them.
The researchers measured the wind speed by observing how light changes when it’s moving towards or away from them, known as the Doppler effect. The high-speed iron found was found to be ejecting in multiple directions, providing data that indicated an impressive wind velocity. The temperature of the gas matched predictions, reaching around 25 million degrees Celsius.
While previous theories suggested that shockwaves from supernovae and intense star formation heated surrounding gas, XRISM has confirmed that the outflow is strong enough to expel four solar masses of gas from the galaxy each year. However, it remains unclear what happens to an additional three solar masses, creating a mystery that future studies will aim to resolve.
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