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Jan. 31 (UPI) -- The cosmos' composition is in constant flux. As old stars die and new stars are born, the universe's elemental building blocks change and evolve. "The universe went through some very interesting changes, where all of a sudden the periodic table -- the total number of elements in the universe -- changed a lot," Jennifer Johnson, a professor of astronomy at Ohio State University, said in a news release.
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Johnson is the author of a new paper -- published in the journal Science -- that provides an overview of the evolution of the universe's elements, the building blocks of all matter.
The crowded nature of the periodic table is a very modern development.
"For 100 million years after the Big Bang, there was nothing but hydrogen, helium and lithium. And then we started to get carbon and oxygen and really important things," Johnson said. "And now, we're kind of in the glory days of populating the periodic table."
All elements were forged by stars.
The Big Bang mostly generated hydrogen and helium, but the as the first stars were born, new elements were formed. When the earliest generations of stars died, they spewed new elements into interstellar space. The new building blocks formed new generations of stars, which forged new elements.
As Johnson recounts in her review, high-mass stars fuse elements more quickly than low-mass stars. High-mass stars, for example, turn hydrogen and helium into carbon, and convert carbon into magnesium, sodium and neon. High-mass stars also die more violent deaths. The elemental ejecta of their explosive supernova -- oxygen, silicon and selenium, for example -- provide interstellar space with chemical complexity.
Low-mass stars also forge elements, but at a more relaxed pace. They too turn hydrogen and helium into carbon. And when low-mass stars die, white dwarfs are left behind. When white dwarfs merge and explode, they also spew elements -- calcium or iron, mostly -- into interstellar space.
Because stars don't live and die at the same time, generations overlap and elements are forged on a variety of timescales. As such, the building blocks of matter are ever-changing.
"One of the things I like most about this is how it takes several different processes for stars to make elements and these processes are interestingly distributed across the periodic table," Johnson said. "When we think of all the elements in the universe, it is interesting to think about how many stars gave their lives -- and not just high-mass stars blowing up into supernovae. It's also some stars like our sun, and older stars. It takes a nice little range of stars to give us elements."
