PARIS – Australian astronomers on Sunday said they had found a star 13.6 billion years old, the most ancient ever seen. It formed just a couple of hundred million years after the birth of the universe, they believe.
Previous contenders for the title of oldest star are around 13.2 billion years old.
Stefan Keller at the Australian National University in Canberra, said the Methuselah star is — in cosmic terms — close to us. It lies in our own galaxy at a distance of around 6,000 light-years from Earth.
“The telltale sign that the star is so ancient is the complete absence of any detectable level of iron in the spectrum of light emerging from the star,” he said.
The early universe was filled with hydrogen, helium and a trace of lithium. All the other elements that we see today were forged in stars that exploded at the end of their life.
One way of determining stellar age is iron, whose content in a star enriches with every successive birth. Thus the lower the iron content in a star’s light spectrum, the older it is.
The progenitor of this star was material from a star whose mass was roughly 60 times that of the sun and exploded as a low-energy supernova, according to the paper, published in the journal Nature.
Previous sweeps of the sky have turned up four other stars with similar very low iron content, which suggests that such supernovas played a vital role in creating stars and shaping galaxies in the early universe, it said.