‘Magic number’ 34

Physicists may have found a new “magic number” — a quantity of protons or neutrons that gives an atomic nucleus unusual stability.

The most common magic numbers are two, eight, 20, 28, 50, 82 and 126; these total numbers of protons and neutrons typically complete “shells” that are similar to the  electron shells  of chemical elements. But new  research published  October 10 in  Nature  shows that 34, not 28, neutrons may fill a shell in the nucleus of calcium-54, a radioactive variant, or isotope, of calcium.

Uncommon magic numbers occur in isotopes like calcium-54 that have far more neutrons than protons. To make calcium-54, a team of physicists used beryllium to strip protons from a high-energy particle beam of scandium-55 and titanium-56. The team then measured the energy gaps between ground and excited states in calcium-54 nuclei and found they were larger than those for similar isotopes.

The new magic number could help scientists understand how atomic nuclei are formed in stars.