Supermassive Black Holes Can Render Exoplanets Uninhabitable

Supermassive black holes (SMBHs) can make exoplanets uninhabitable, even at great distances from the black hole. This effect occurs regardless of the exoplanet's distance from its host star. New research details how these powerful cosmic objects impact planetary habitability.

The study, published in *The Astrophysical Journal*, focuses on the role of SMBHs. Jourdan Waas from the Florida Institute of Technology led the research. The paper is titled "The Impact of Supermassive Black Holes on Exoplanet Habitability. I. Spanning the Natural Mass Range."

Supernovae have long been studied for their effects on planetary habitability. They release powerful radiation and shock waves. These events can strip away atmospheres or destroy planets. However, an active galactic nucleus (AGN), which is a feeding SMBH, can be far more energetic over a sustained period.

AGNs create winds that influence their host galaxies. The researchers examined two types of AGN winds: energy-driven and momentum-driven. Energy-driven winds have a stronger impact on exoplanet atmospheres. They are more effective at heating and stripping away these atmospheres.

The study found that more massive SMBHs lead to more rapid atmospheric mass loss in exoplanets. This process degrades habitability. Increased SMBH mass results in higher atmospheric heating and elevated temperatures. It also causes greater molecular thermal velocities and enhanced mass loss. These effects diminish with increasing distance from the galactic center.

Researchers also investigated ozone depletion. AGN winds, particularly ultrafast outflows, can contribute to ozone depletion in Earth-like atmospheres. Ozone depletion increases with black hole mass and proximity to the AGN. More massive black holes produce more powerful AGN winds and more nitrogen oxides, leading to greater ozone depletion.