Science News - USA (2021-11-20)

T. TIBBITTS

20 SCIENCE NEWS | November 20, 2021

FROM TOP: FRIB; T. TIBBITTS

FEATURE

I

nscribed on an Italian family’s 15th century

coat of arms and decorating an ancient

Japanese shrine, the Borromean rings are

symbolically potent. Remove one ring from the

trio of linked circles and the other two fall apart.

It’s only when all three are entwined that the

structure holds. The rings have represented the

concepts of unity, the Christian Holy Trinity and

even certain exotic atomic nuclei.

A rare variety, or isotope, of lithium has a

nucleus that is made of three conjoined parts.

Lithium-11’s nucleus is separated into a main

cluster of protons and neutrons flanked by two

neutrons, which form a halo around the core.

Remove any one piece and the trio disbands, much

like the Borromean rings.

Not only that, lithium-11’s nucleus is enormous.

With its wide halo, it is the same size as a lead

nucleus, despite having nearly 200 fewer pro-

tons and neutrons. The discovery of lithium-11’s

expansive halo in the mid-1980s shocked scien-

tists (SN: 8/20/88, p. 124), as did its Borromean

nature. “There wasn’t a prediction of this,” says

nuclear theorist Filomena Nunes of Michigan State

University in East Lansing. “This was one of those

discoveries that was like, ‘What? What’s going on?’ ”

Remove one of the three

Borromean rings and

the whole structure

falls apart. Some atomic

nuclei have the same

property.

With a new particle accelerator, scientists set their sights on

unexplored atomic territory By Emily Conover

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