Black Hole: Cosmic Gardener Can Actually Cultivate Life

The most destructive monster in the universe is probably twice as big as the cosmic gardener. New research shows that under the right conditions, the strong radiation of active black holes can help shield and maintain distant planetary life, rather than erase it – challenging our assumptions about the possible existence of life in the universe.

A study published February 20 in the journal Astrophysics reveals how radiation from the active galactic nucleus (AGNS)—a strongly bright area surrounding the strongly bright areas feeding supermassive black holes— triggers protective atmospheric changes in certain planets, potentially creating a hospitality environment that allows life to reproduce.

In the center of the Milky Way, most large galaxies are supermassive black holes. When interstellar gases fall into these cosmic giants, they transform into “active modes” and explode high-energy radiation on the galaxy. Traditional views suggest that this radiation will sterilize nearby planets, but the Dartmouth and Exeter University research team found a surprising twist.

“Once life exists and is filled with atmosphere, radiation becomes less destructive, and may even be a good thing,” said Kendall Sippy, lead author of the study. “Once the bridge passes, the Earth is more resilient to UV radiation and protected from potential extinction events.”

The team used advanced computer simulations to study how AGN radiation influences Earth-like planets with different atmospheres. Their findings suggest that on planets where life has established and produces a lot of oxygen, strong UV radiation actually enhances the protective ozone layer rather than destroys it.

This protection effect occurs because high-energy light splits oxygen molecules into individual atoms that recombinate to form ozone. As the ozone layer is established in the upper atmosphere, it will bring more and more dangerous radiation back into space – producing a self-reinforced shield.

The same process happened on Earth about 2 billion years ago when the first microorganism that produced oxygen changed our atmosphere. Radiation from the sun helps early life oxidize the atmosphere, accumulate ozone, and create conditions for the evolution of more complex organisms.

“If life can quickly oxidize the atmosphere of a planet, ozone can help regulate the atmosphere, thus benefiting the conditions needed for life,” explains Jake Eager-Nash, a postdoctoral researcher at the University of Victoria. “Without the feedback mechanism of climate regulation, life may disappear quickly.”

The eager Nash and colleagues tested the extreme situation in the simulation. Even though the Earth is too far from our galaxy’s black hole and the impact of Sagittarius A is affected by radiation, the researchers mimicked what would have happened if the Earth was closer to the hypothetical AGN, exposing it to radiation billions of times more intense than we experienced.

As a result, contrasting pictures were drawn based on the atmospheric development of the planet. In a poor atmosphere similar to the early days of the Earth, strong radiation may prevent life from appearing. However, with modern oxygen levels, the atmosphere will rapidly produce protective ozone.

“With modern oxygen levels, it will take several days, which will mean life can survive,” the eager Nash noted. “We were surprised at how quickly we responded to the ozone levels.”

The researchers also explored what happens to Earth-like planets of different galaxy types. In “red nuggets” galaxies like NGC 1277, planets do not expect the results of the planet, where stars are densely packed near central black holes. However, planets in our Milky Way or in more diffuse galaxies such as Messier-87 will have a better chance of maintaining habitable conditions, as their stars are farther away from the radiation of AGN.

This study represents an interdisciplinary collaboration that begins with an opportunity worthy of the plot of science fiction. In 2023, Ryan Hickox, a research co-author of Ryan Hickox, professor of physics and astronomy at Dartmouth, booked the passage for the Mary 2 Queen 2 ocean liner on Dartmouth, so he could take his dog Benjamin to England for a leave of absence. On board, he met Nathan Mayne, an astrophysicist at the University of Exeter, who was a guest speaker.

Their onboard dialogue revealed a shared interest in radiation effects, and they realized that Mayn’s ancient software was originally designed to model solar radiation on exoplanet atmospheres to study the more powerful light that activates black holes.

This Marine Thought Conference created a great opportunity for Sippy, who has a keen interest in Hickox’s lab, is interested in Hail Holes, and works with Eager-Nash, a PhD student at Mayne’s Lab.

Sispy explains their calculation method. “It returns a graph of impacting the surface at different wavelengths and the concentration of each gas in the model atmosphere at different time points.”

The protective feedback loop found in an oxygen-rich atmosphere even surprised the researchers. “Our collaborators don’t work on the radiation of black holes, so they are not familiar with the spectrum of black holes and the stars AGNs can get are much more distances than you, depending on your distance,” Hickox said.

He added: “This is an insight you can only really gain by combining different expertise.”

After graduation, Sippy conducted research at Middlebury College with McKinley Brumback, a former Hickox Laboratory PhD student who now studies assistant professor of neutron star X-ray binary binary. Brumback contributed her expertise in the system where neutron stars draw matter from normal stars, resulting in similar radiation effects, but faster than AGN’s timeline.

As astronomers continue to map potential habitable areas around stars, this study suggests that we may also need to consider the size of the galaxy. These findings expand our understanding of where life may appear and persist in the universe, perhaps even in the shadow of nature’s most destructive forces, the radiation that initially seemed hostile to eventually nurture and protect the developing biosphere.

For planets, enough to develop life that produces oxygen before encountering strong radiation, the terrible energy of the black hole may paradoxically become gardeners who help life flourish rather than end it.