New Constraints on Primordial Black Holes as Dark Matter

A recent paper by Abraham Loeb from Harvard University, titled 'Excluding Primordial Black Holes as Dark Matter Based on Solar System Ephemeris,' presents findings that challenge the hypothesis that primordial black holes (PBHs) could constitute dark matter. The study, accepted for publication in the Research Notes of the American Astronomical Society, utilizes the Solar System ephemeris to rule out a significant portion of the mass range ($10^{18}$-$10^{22}$g) where PBHs were previously considered viable candidates for dark matter.

The research hinges on the observation that the external mass enclosed within 50 astronomical units (au) from the Sun has not changed by more than approximately $5 \times 10^{-14}$ solar masses per year in recent decades. This stringent constraint effectively eliminates the possibility that a substantial number of PBHs exist within this mass range, as their gravitational influence would have altered the Solar System's dynamics more noticeably.

This finding has significant implications for our understanding of dark matter, a mysterious substance that makes up about 27% of the universe's mass-energy content. By narrowing down the possible candidates, scientists can better focus their efforts on other potential explanations and refine their models of cosmic evolution.

For further reading, the paper can be accessed at arXiv:2408.10799.