Scientists have discovered what they claim to be the oldest stars ever seen. The stars are located near the center of the Milky Way galaxy. The stars date back to 13.6 billion years ago, meaning they were formed just 200 million years after the Big Bang. Louise Howes of the Australian National University, the lead author of the study, said these stars are very close to the center of Milky Way galaxy. They probably have been there since the beginning of the Universe, she said.
The first stars were formed with just three elements
Findings of the study were published in the journal Nature. The oldest of these nine stars is a red giant called SMSS J181609.62 -333218.7, which is located about 25,000 light years away from Earth. It was an ordinary orange dwarf star of 0.8 solar masses, meaning it was slightly smaller and cooler than our Sun. Since these stars have been there for almost the entire age of the universe, they retain vital information in their atmospheres what the universe was like in the beginning.
Howes and her colleagues used the Australian National University’s SkyMapper telescope at the Siding Spring Observatory to search the galactic bulge of Milky Way for stars with ancient chemical compositions. Following the Big Bang, the universe was filled with only hydrogen, helium, and small amounts of lithium. The first stars were forming with just these elements.
The previous record holder was located in the halo of the Milky Way
These first stars were all giants, about 40 times bigger than our Sun. All the heavier elements were produced in these stars. When they died, an enormous explosion called Hypernova spread their heavier elements throughout the cosmos. As a result, the concentration of heavier elements increased in successive generations of stars. Astronomers use the ratio of heavier elements such as iron and carbon with hydrogen to determine the age of stars. The lower the ratio, the older the star.
The oldest of the newly discovered stars, SMSS J181609.62 -333218.7, had no detectable carbon and its iron abundance was 10,000 times lower than Sun. The lack of carbon in this star suggests that it was formed from a Hypernova (the explosion of earlier giant stars). Researchers said it was older than the previous record-holder SMSS J031300.36 -670839.3, which was discovered last year in the halo of the Milky Way.