Black holes about the size of a hydrogen atom could be careening through the solar system unnoticed. But their days of stealth may be numbered.

Two teams of researchers propose methods to search for these tiny, hypothetical objects, which would have the mass of an asteroid. Because they would have formed in the universe’s infancy, they are known as primordial black holes.

If they exist, primordial black holes in this mass range could explain some or all of the universe’s dark matter (SN: 8/7/16). That unknown invisible source of mass exerts gravitational influence on galaxies and, perplexingly, seems to outweigh normal matter by about 6 to 1. Extensive searches for subatomic particles that could explain dark matter have come up empty, putting new focus on primordial black holes (SN: 8/26/24).

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