A team of astronomers from Cornell University have published a new paper titled "New Horizons Observations of the Cosmic Optical Background," which explains that, using new measurements from the New Horizons space probe, the universe is actually physically brighter than they thought. Or at least, it's not completely dark like they expected it to be.
The New York Times sums this up well:
Four billion miles from the sun, far from bright planets and the light scattered by interplanetary dust, empty space was about twice as bright as would be expected Dr. Lauer and his colleagues found. The most likely explanation, he said, was that there were more very faint galaxies or star clusters contributing to the background light of the universe than their models indicated. Or even that black holes in the centers of otherwise undistinguished galaxies were pumping extra energy into the void.
A less exciting possibility, Dr. Lauer said in an email, was that "we messed up and missed a light source or camera artifact that we should have figured out. This is what I worry about the most."
It's also possible that this light source may be coming from so-called "dark matter," suggesting that mysterious material (which comprises some 85% of the cosmos) some of it may not be as dark as believed either. It wasn't until 2018 that scientists were able to calculate just how much non-dark matter is out there. But they may be able to build off of that knowledge to help them find the source of this strange light.
Or maybe it is, as Dr. Lauer suggested, just another one for 2020 to laugh at us.
New Horizons Observations of the Cosmic Optical Background [Cornell University]
Outer Space Just Got a Little Brighter [Dennis Overbye / New York Times]
Image: Bruno Gilli/ESO (CC 4.0)