Early Stars Display Amazing Heavy Chemical Concentrations

A group of astronomers were recently able to discover an agglomeration of very old stars on the outer fringes of the galaxy, which turned out to have a very unique and unexpected chemical composition. Analysis revealed the objects to contain a lot of heavy chemical elements.

According to established theories on stellar formation, heavier elements are produced when large stars reach the end of their burning cycles, and explode as impressive supernovae. But this also implies that the first generation of stars in a galaxy cannot contain too many such chemicals.

Yet, astronomers now discover large amounts of uranium, gold and platinum in some of the earliest stars that exist in the Milky Way. If theories are to be believed, this should not happen. Rather, younger stars should display elevated concentrations of such chemicals, investigators report.

In order for experts to explain this mystery, they conducted a multi-year investigation of 17 weird stars in our galaxy, all of which had been previously shown to contain heavy elements. The European Southern Observatory (ESO) used its entire fleet of Chilean telescopes for the study.

“In the outer parts of the Milky Way there are old 'stellar fossils' from our own galaxy's childhood. These old stars lie in a halo above and below the galaxy's flat disc,” University of Copenhagen Niels Bohr Institute astrophysicist Terese Hansen explains.

The expert was the lead author of a new study detailing the work, which was published in the November 14 issue of the scientific journal Astrophysical Journal Letters. She and her team even managed to calculate the orbital motions of all 17 stars targeted by the investigation.

“In a small percentage – approximately 1-to-2 percent of these primitive stars – you find abnormal quantities of the heaviest elements relative to iron and other 'normal' heavy elements,” she explains.

The team determined that there are two possible explanations for these stars. In one scenario, some of the earliest stars may have existed in binary systems. When one of them went supernova, it would have directly transmitted heavier chemical elements to the other, Space reports.

But Hansen says that only 20 percent of stars exist in binary systems. As such, this explanation cannot be the norm, only a special case. More likely, early supernovae were able to shoot jets of heavy chemicals in several directions, seeding stellar nurseries with gold and platinum, among other elements.

“In the supernova explosion the heavy elements like gold, platinum and uranium are formed and when the jets hit the surrounding gas clouds, they will be enriched with the elements and form stars that are incredibly rich in heavy elements,” Hansen concludes.