An international research collaboration led by the University of Surrey’s Nuclear Physics Group has overturned the long-standing belief that the atomic nucleus of lead-208 (²⁰⁸Pb) is perfectly spherical. The discovery challenges fundamental assumptions about nuclear structure and has far-reaching implications for our understanding of how the heaviest elements are formed in the universe.

Lead-208 is exceptionally stable due to being a “doubly magic” nucleus—and is the heaviest that we know of. However, a new study published in Physical Review Letters used a high-precision experimental probe to examine its shape and found that rather than being perfectly spherical, the nucleus of lead-208 is slightly elongated, resembling a rugby ball (prolate spheroid).

Dr. Jack Henderson, principal investigator of the study from the University of Surrey’s School of Mathematics and Physics, said, “We were able to combine four separate measurements using the world’s most sensitive experimental equipment for this type of study, which is what allowed us to make this challenging observation. What we saw surprised us, demonstrating conclusively that lead-208 is not spherical, as one might naively assume. The findings directly challenge results from our colleagues in nuclear theory, presenting an exciting avenue for future research.”