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The pulsar timing measurements must be extremely precise to measure the gravitational wave background correctly.

Collaborations such as the NANOGrav Physics Frontiers Center use pulsars to study the gravitational wave background, which can help researchers understand the early Universe and the prevalence of gravitational-wave sources such as supermassive black-hole binaries.

"They are interesting for other reasons too, as since the recent innovation of gravitational wave astronomy, there have been discoveries of binary black hole mergers, which can be explained if PBHs exist in large numbers. But despite these strong reasons for their expected abundance, we have not seen any directly, and now we have a model which should explain why this is the case."

In this case, the team used a novel approach to correct the leading model of PBH formation from cosmic inflation so it better aligns with current observations and could be further verified with upcoming observations by terrestrial gravitational wave observatories around the world.

"Our study suggests there should be far fewer PBHs than would be needed if they are indeed a strong candidate for dark matter or gravitational wave events."