Black holes, the great voids that gravitationally let nothing escape, may be responsible for the light that made our universe what it is today. This seeming contradiction is because the gravity of black holes extends beyond their event horizons and can create environments that glow brightly in the night.

As a reminder, when the universe was formed, everything was energy. Over time, it expanded and cooled, allowing first ionized particles to form, and eventually, about 400,000 years after T=0, it cooled enough for atoms to form. These neutral atoms formed a universal fog that would have hidden the first light of the first stars from view. Some combination of things, however, emitted ultraviolet light capable of reionizing that gas and creating the transparent universe we enjoy today.

One of JWST’s primary tasks is to identify what all is responsible for that reionization, but impatient astronomers decided to do what they could using other scopes, looking at our modern universe to understand what may have happened in the past. According to a University of Iowa press release: ...astronomers identified a black hole, a million times as bright as our sun, that may have been similar to the sources that powered the universe’s reionization. That black hole … is powerful enough to punch channels in its respective galaxy, allowing ultraviolet photons to escape and be observed. 

This work is published in the Monthly Notices of the Royal Astronomical Society, and corresponding author Phil Kaaret explains: The implication is that outflows from black holes may be important to enable escape of the ultraviolet radiation from galaxies that reionized the intergalactic medium.

Let’s break that down. Material flowing in toward the supermassive black holes in the centers of galaxies heats up. This generates light and a magnetic field. The magnetic field then creates outflows of material that clear away stuff that might block the light from the galaxy’s center. That light – the ultraviolet light capable of ionizing hydrogen – shone out and changed our universe forever.

So while we may think of black holes as monsters waiting to devour stars and planets – which they are – they are also the necessary foundations for all the physics that made our modern universe possible.

The Universe is full of wonderful contradictions.

More Information

University of Iowa press release

“Rapid turn-on of a luminous X-ray source in the candidate Lyman continuum emitting galaxy Tol 0440-381,” P Kaaret, J Bluem, and A H Prestwich, 20221 December 14, Monthly Notices of the Royal Astronomical Society