Scientists may have finally found where the 'missing half' of the universe's matter is hiding

An illustration of the Milky Way in the center of a blue cloud of gas.

The universe's missing matter may have finally been found.

Astronomers think regular matter — that is, the stuff that isn't dark matter — makes up about 15% of the universe's total mass. However, for years, researchers have run into a problem when trying to quantify it: They haven't been able to find about half of that "normal" matter in the stars, galaxies and other space structures we can see.