Most of the matter in the universe is invisible — it produces no detectable energy. Yet we know it’s there because we see it pull on the visible matter around it. The most popular idea is that this “dark matter” consists of some new kind of subatomic particle. So far, though, efforts to find these particles have come up empty.

Some scientists suggest that instead of particles, dark matter consists of black holes. These black holes would have formed a fraction of a second after the Big Bang, when dense pockets of matter collapsed under their own weight. These “primordial” black holes would be up to a few dozen times the mass of the Sun. The recent discovery of mergers of pairs of black holes in that size range seems to bolster the idea.

One recent study said that we might be able to see the effects of these black holes in the “haloes” of small galaxies. The gravity of the black holes would change the way the normal stars in the galaxies are distributed.

Another study looked for primordial black holes to alter the view of exploding stars. The gravity of a black hole between Earth and such a star would act as a lens, changing the brightness of the explosion. But the study didn’t find a single instance of such an effect. Based on that, the researchers concluded that black holes could account for no more than 40 percent of dark matter.

So the search for dark matter — of whatever size — continues.

Script by Damond Benningfield