Much of the universe's regular "baryonic" matter is spread through intergalactic space and in diffuse halos around galaxies, researchers proposed after studying the behavior of fast radio bursts emitted from deep space.

The universe has two kinds of matter. There is invisible dark matter, known only because of its gravitational effects on a grand scale. And there is ordinary matter such as gas, dust, stars, planets and earthly things like cookie dough and canoes.

Decades ago, astronomers estimated that “ordinary” matter (basically everything that isn’t dark matter or dark energy) makes up 5% of the universe. There was just one problem—they had no idea where most of it was.