Explosions of universe's first stars spewed powerful jets: study

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WASHINGTON, May 8 (Xinhua) -- Astrophysicists found that the first stars after the Big Bang exploded not like spherical balls as previously thought but in an asymmetric fashion, thus serving as seeds for the second generation of stars and today's galaxies.

The study published on Wednesday in the Astrophysical Journal showed that those stars had blown apart and spewed forth jets that were violent enough to eject heavy elements into neighboring galaxies.

Within the cores of these first stars, extreme, thermonuclear reactions forged the first heavier elements, including carbon, iron, and zinc, according to the study.

Researchers from Massachusetts Institute of Technology (MIT) and their Japanese collaborators identified a strong abundance of zinc in an ancient star among the universe's second generation of stars, which could have acquired such amount of zinc thanks to asymmetric explosion of one of the very first stars. It is 5,000 light years away.

"When a star explodes, some proportion of that star gets sucked into a black hole like a vacuum cleaner," said the paper's co-author Anna Frebel, an associate professor of physics at MIT.

"Only when you have some kind of mechanism, like a jet that can yank out material, can you observe that material later in a next-generation star," said Frebel.

This is the first observational evidence that an asymmetric supernova took place in the early universe, according to the researchers.

The simulation showed that only an aspherical, jet-ejecting supernova, about five to 10 times more explosive than people have thought before, could explain the star's zinc makeup.

The findings may change scientists' understanding of the universe's history, especially a period during which the gas in the universe shifted from being completely neutral, to being ionized, a state that made it possible for galaxies to take shape.

Frebel said the first stars might much more energetic that help ionize the universe and shoot heavy elements into neighboring "virgin galaxies" that had yet to form any stars of their own.

"Once you have some heavy elements in a hydrogen and helium gas, you have a much easier time forming stars, especially little ones," said Frebel. Enditem

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