At the center of most large galaxies, including our Milky Way, sits a supermassive black hole.
These powerful objects sometimes enter active galactic nucleus (AGN) mode, where they pull in gas and blast high-energy radiation across their galaxies.
This radiation might seem deadly, but a new study suggests it could actually help life survive under the right conditions.
Can black hole radiation support life?
Scientists from Dartmouth and the University of Exeter ran computer simulations to study how AGN radiation affects planets.
Their findings, published in The Astrophysical Journal, show that AGN radiation can help protect a planet’s atmosphere—if life is already present.
Lead researcher Kendall Sippy explains that once a planet has oxygen in its atmosphere, the high-energy light from an AGN can trigger chemical reactions that strengthen the planet’s ozone layer. This layer blocks harmful radiation, making the planet more resistant to extinction events.
The researchers tested their model on different Earth-like planets, each with varying levels of oxygen. They found that the more oxygen a planet had, the faster ozone would form in its upper atmosphere.
This process is similar to what happened on Earth two billion years ago, when the first oxygen-producing microbes started releasing oxygen into the air. As oxygen levels increased, Earth’s ozone layer grew, protecting the planet from harmful UV rays and allowing life to thrive.
“If life can oxygenate a planet quickly, ozone will regulate the atmosphere and create stable conditions for life to grow,” says Jake Eager-Nash, a study co-author and postdoctoral researcher at the University of Victoria.
The team ran simulations to see what would happen if Earth were much closer to a black hole in AGN mode. They recreated Earth’s early atmosphere, which lacked oxygen, and found that the intense radiation would likely prevent life from forming. However, once oxygen levels reached modern levels, an ozone layer would quickly form and shield life from harmful radiation.
“With today’s oxygen levels, the ozone layer could form in just a few days, which means life might survive,” says Eager-Nash.
The researchers also tested what might happen in different galaxies. In compact galaxies like NGC 1277, where stars are packed close to the AGN, the radiation would be lethal. But in larger galaxies like the Milky Way or Messier-87, where stars are spread out, planets would be safer from the AGN’s effects.
This study was made possible by a chance meeting. Dartmouth professor Ryan Hickox met astrophysicist Nathan Mayne from the University of Exeter while traveling on the Queen Mary 2. Their discussion led to the idea of using Mayne’s PALEO software—originally designed to study solar radiation on exoplanets—to model the effects of AGN radiation on planets.
With help from researchers like Eager-Nash and McKinley Brumback, the team developed a powerful computer model that could track how radiation interacts with a planet’s atmosphere over time.
“Without the right mix of expertise, we might never have realized how AGN radiation can play a role in making planets more habitable,” says Hickox.
The discovery opens new doors for studying how life could exist in extreme environments. While Earth is too far from Sagittarius A (our galaxy’s black hole) to be affected, scientists now know that planets in certain conditions could use black hole radiation to their advantage.
“This research changes how we think about the impact of black holes on planets,” says Sippy. “Under the right conditions, what seems deadly could actually be a force for life.”
