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Most Lithium in the Universe Is Forged in Exploding Stars

The recurring explosions of white dwarf stars produce the vast majority of this important element

Artist concept of a binary system similar to the one that originated the nova Sagittarii 2015 N.2. (David A. Hardy/PPARC)
smithsonian.com

Whether it’s in medication or your smartphone battery, lithium is one of the most common elements in modern life—and like most other elements, scientists have long-suspected that it comes from the stars. But for years researchers have puzzled over which cosmic phenomenon is responsible for creating the lightest solid element on the periodic table. Now, astronomers may have located the missing piece of the puzzle: an exploding nova.

The lightest elements in the universe—hydrogen and helium—were formed in the Big Bang. But along with these light elements, were some amounts of others, including lithium and beryllium. Scientists believe that 25 percent of the lithium was created in our universe's infancy—before even most stars had formed. Majority of the heavier elements, however, were generated later in the churning heat of stars. And while researchers know lithium likely didn't form this way, where that remaining lithium was created has long remained a mystery.  

Researchers had hints that novae could generate this element, but no one had ever spotted the creation in action, until now. According to a new study published in the Monthly Notices of the Royal Astronomical Society, a group of researchers from the Institute of Astrophysics of Andalusia recorded a recent nova that blasted off huge amounts of an unstable isotope, beryllium-7, that degrades into lithium relatively quickly. Within 53.22 days, half of any given amount of Be-7 will transform into lithium.

"We’re talking about an amount of lithium ten times greater than that in the Sun," lead researcher Luca Izzo says in a statement. "With these amounts in mind, two similar novae a year would suffice to account for all the lithium in our galaxy, the Milky Way. Novae seem to be the predominant source of lithium in the universe."

While nova may sound similar to a supernova, they are very different beasts. While supernovae are massive, one-time stellar detonations, novae are repetitive phenomena that occur when white dwarf stars absorb hydrogen from another nearby sun, Michael Shara, curator of the Department of Astrophysics at the American Museum of Natural History, tells Smithsonian.com.

“Each time the white dwarf accretes about 1/100,000 of its companion’s mass, it has this explosion on its surface, which blows away its [hydrogen] envelope,” Shara says. “Think of the supernova as the death of the star. A nova is sort of like a haircut to the white dwarf.”

What’s most surprising about this study is how strong the data are. According to Shara, who was not involved with the work, Izzo and his team were not only looking in the right place at the right time, but had the right equipment to gather strikingly convincing data.

“That often doesn’t happen,” Shara says. “Their dataset is just so much better than anything anyone else has ever collected before...as well as a very strong analysis of the data. Those two together make a really strong case that they’ve found the right answer.”

Still, Shara says it’s important that another team of astronomers using different telescopes also spots a nova giving off this lithium-producing isotope in order to further solidify Izzo’s findings. While these scientists may have found the missing puzzle piece, it will take more research to put it in the right place.

About Danny Lewis

Danny Lewis is a multimedia journalist working in print, radio, and illustration. He focuses on stories with a health/science bent and has reported some of his favorite pieces from the prow of a canoe. Danny is based in Brooklyn, NY.

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