

Lurking in the heart of most large galaxies is a supermassive black hole holding it all together. According to new research from the University of California Santa Cruz, these supermassive black holes could also spell eventual doom for galaxies. They might not just be gobbling up nearby stars, but could also rob a galaxy of all the primordial material necessary to keep star formation chugging along.

When a galaxy is young and fresh, star formation is at its peak. As galaxies age, star formation slows and eventually stops. This process is called quenching, and a team led by UC Santa Cruz’s Ignacio Martín-Navarro says supermassive black holes are playing a critical role in extinguishing galaxies.

Stars form from clouds of cold interstellar hydrogen that begin clumping up due to gravity. These proto-stars eventually get massive enough that they can fuse hydrogen and become main sequence stars, but some just end up as smaller brown dwarfs. When a galaxy runs out of cold gas stores, it doesn’t form any more stars. The UC Santa Cruz team now has evidence to back up the hypothesis that black holes are essentially expelling much of this gas via high-energy jets and leading to the premature death of galaxies.

Martín-Navarro and his team used data from the Hobby-Eberly Telescope Massive Galaxy Survey to analyze the light from distant (and thus very old) galaxies. The team built a model of star formation in these galaxies based on observed wavelengths, and then compared that with black holes of different masses. The result was a strong correlation with the mass of a black hole and the rate of quenching.



According to the study’s results, the larger a supermassive black hole is, the faster star formation is quenched. There are even some galaxies with similar star masses, but different black holes, and those with larger black holes do indeed quench faster. This line of inquiry is far from finished, though. It looks like there’s a correlation, but we don’t fully understand the mechanism by which black holes can expel gas and into space.

It’ll be interesting if scientists can work out all the details of quenching, but there’s little practical application. It’s not like we can do anything to stop this process, and yes, this all applies to the Milky Way. Our own galaxy is already starting to slow down as cold gas is used up. In a few billion years, the Milky Way could be a stellar graveyard thanks to our friendly neighborhood supermassive black hole.