Black hole jets may decide the fate of entire galaxies
Astronomers have found that plasma jets from supermassive black holes can heat the circumgalactic medium, preventing gas from cooling and forming new stars. This mechanism helps explain why some galaxies do not produce stars as rapidly as their gas reservoirs might suggest.
Why it matters
This discovery solves a long-standing mystery in galactic evolution and deepens our understanding of how black holes influence the life cycle of galaxies.
Galaxies can contain hundreds of billions of stars, but every one of those stars begins with cold, dense gas. Large galaxies, including the Milky Way, are surrounded by an enormous reservoir of this material known as the circumgalactic medium, or CGM.
The CGM extends roughly 10-20 times farther than the visible part of a galaxy. Over time, some of this gas can cool, flow inward, gather into dense clouds, and eventually form new stars. Because stars give rise to planets and the conditions necessary for life, the CGM plays an important role in a galaxy's long term evolution.
Yet astronomers have faced a persistent puzzle. If galaxies are surrounded by so much potential star-forming material, why do they not produce far more stars? Something appears to be preventing much of that gas from cooling and falling inward.
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