Physics has seven magic numbers. An atom with a magic number of protons or neutrons is super stable. When both the protons and neutrons are magic, that's a double magic atom. There are only six of them. Until now.

The seven magic numbers are 2, 8, 20, 28, 50, 82, and 126. They are the number of nucleons - which can be either protons or neutrons - you need to fill up the shells found in the atomic nucleus. The completely filled shells cause the atomic nucleus to be more tightly bound together than simple calculations would predict, meaning the magic atoms are unusually stable. (These numbers are not the number of electrons you need to fill up the various orbital variances, although there is some overlap. Those are 2, 8, 18, 32, and 50.)

So, if both the neutrons and protons happen to be magic numbers, the atom is not only extra stable, but its nucleus is also rigidly spherical, which is very unusual and helps observers confirm the doubly magic properties of the atom. These isotopes - which include helium-4 (2 protons and 2 neutrons, and one of the most abundant isotopes in the universe), lead-208 (82 protons and 126 neutrons, and the heaviest stable atom), and the pair of calcium-48 and nickel-48 (the former has 20 protons and 28 neutrons, while the latter is vice versa). The latest to be discovered is tin-132, which has 50 protons and 82 neutrons.

This isotope is special because it's the first double magic isotope to also be both radioactive and neutron-rich. This discovery of such an isotope will help physicists better study the workings of what is known as the r-process, which is thought to be responsible for the formation of about half of all elements in the universe heavier than iron. Short for rapid process, the r-process occurs in collapsing supernovae where massive amounts of free neutrons are released and then captured by nuclei, fomenting the creation of heavy elements.

Tin-132 is thought to be very close to the sort of nuclei that are most often featured in such processes, and its greater stability allows physicists the opportunity to more closely analyze its properties and determine just how the r-process works.

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[Nature]