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Astronomers find evidence of catastrophic event in ancient galaxy

"These stars have up to a thousand times more neutron capture elements than any other stars observed in similar galaxies," said astronomer Alexander Ji.
By Brooks Hays   |   Updated March 22, 2016 at 3:31 PM

BOSTON, March 21 (UPI) -- Astronomers have struggled to identify the origins of the heaviest elements, like gold and lead. A tiny, ancient galaxy may offer clues.

The Big Bang produced the lightest elements on the periodic table, while heavier elements were forged by stellar fusion and supernovas. Now, astronomers think the heaviest elements are created by collisions between neutron stars.

The proof lies inside a recently identified nearby galaxy called Reticulum II. The galaxy is found in the southern constellation Reticulum.

A remnant of the early universe and home to some of the earliest stars, the galaxy's simple chemistry makes it an ideal target for researchers trying to understand stellar evolution and element creation.

"Reticulum II has more stars bright enough for chemical studies than any other ultra-faint dwarf galaxy found so far," Josh Simon, an astronomer at the Carnegie Science Foundation, said in a news release.

Most elements are formed when two atomic nuclei fuse, but elements heavier than zinc are born from a process called neutron capture, whereby elements acquire neutrons. The neutrons, acquired one by one, decay into protons and form a new element.

Reticulum II has a high concentration of elements formed by neutron capture.

"These stars have up to a thousand times more neutron capture elements than any other stars observed in similar galaxies," said Alexander Ji.

Ji is an astronomer at MIT and lead author of a new paper on the subject, published this week in the journal Nature.

The unusually high concentration of neutron capture elements in Reticulum II suggests these heavier elements are formed by rarer cosmic phenomena like neutron star collision -- as opposed to more common phenomena like supernovas.

"Producing rapid neutron capture elements in a neutron star merger explains these observations beautifully," said co-author Anna Frebel, also a researcher at MIT.

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