Scientists Just Discovered Outer Space Isn’t Pitch Black

On Sunday, Nov. 15, four astronauts ascended to space as part of the NASA and SpaceX joint Crew-1 mission to the International Space Station. As they left Earth’s atmosphere, they were greeted by the inky darkness of space. Or were they?

According to a new study scheduled to be published in The Astrophysical Journal, scientists have determined that outer space isn’t pitch black at all — it’s actually filled with light. While we all know that stars emit plenty of visible light, we’ve generally assumed that space, as a whole, is completely dark in the absence of stars. And it is definitely dark, but apparently, it’s not that dark.

Astronomer Tod Lauer of Arizona’s National Optical Astronomy Observatory and a team of researchers have been studying light in deep space through NASA’s New Horizons mission, a project whose initial subject was Pluto. But after completing a six-month residency at the dwarf planet, the New Horizons spacecraft was sent into deep space, and it’s currently more than four billion miles away from Earth. At that distance away from the sun, it’s the perfect spacecraft to capture images of the true darkness of space.

Lauer and his team studied the emptiest of these photographs, the ones without any bright objects in them. They processed them to remove all light from known sources, including relatively nearby stars, then took out even more light from galaxies that are hypothesized to exist, but have yet been found. What the scientists were left with were “pure” images of deep space without any light pollution. However, they still found light — lots of it.

"They're saying that there's as much light outside of galaxies as there is inside of galaxies, which is a pretty tough pill to swallow, frankly," Michael Zemcov, an astrophysicist at Rochester Institute of Technology, told NPR, who originally reported the story.

Where is this mysterious light coming from? Well, the researchers aren’t entirely sure. They theorize it might be from stars or galaxies we haven’t discovered yet, or it could be something entirely new. Whatever the source, this light will certainly be a hot topic of discussion — and the subject of plenty of research — for some time to come.