The oldest known star in the universe, which formed shortly after the Big Bang 13.7 billion years ago, was discovered by The Australian National University astronomers.
The star is located 6,000 light years from Earth and was discovered using the ANU SkyMapper telescope at the Siding Spring Observatory. It is one of the 60 million stars photographed by SkyMapper in its first year. The discovery gives the researchers an opportunity to study the chemistry of the first stars, which can help them better understand what the Universe was when it was newly formed.
"This is the first time that we've been able to unambiguously say that we've found the chemical fingerprint of a first star," said lead researcher, Dr Stefan Keller of the ANU Research School of Astronomy and Astrophysics in a press statement. "This is one of the first steps in understanding what those first stars were like. What this star has enabled us to do is record the fingerprint of those first stars."
According to researchers, finding such a star is a one in a million chance. All credit for this discovery must be given to the ANU SkyMapper telescope that is unique in its ability to find stars with low iron from their color.
After studying the composition of this star, researchers revealed that it was formed during the birth of a primordial star, which had a mass 60 times greater than that of the Sun. "The "recipe" of this ancient star is very "different" from that of stars like the sun. While to make stars like the sun, you require hydrogen and helium from the Big Bang and iron 1,000 times the Earth's mass, the newly discovered star requires no more than an Australia-sized asteroid of iron and lots of carbon," says Dr Keller.
As explained by the Massachusetts Institute of Technology, the Big Bang produced hydrogen and helium particles that became stars. These massive stars did not live long and their deaths, in supernovae, produced new elements, namely iron, carbon and oxygen. Contrary to previous beliefs that suggested primordial stars died in extremely violent explosions, which polluted huge volumes of space with iron, the newly discovered ancient star reveals signs of other pollutants like carbon and magnesium but no iron.
Astronomers can determine the age of a star based on iron levels. Each subsequent supernova produces more iron and younger stars contain higher levels of the element than ancient stars.
The newly discovered star is named SMSS J031300.36-670839.3. The upper limit of the level of iron of this star is so low that researchers deemed it to be a second generation star. This led researchers to speculate that the supernova responsible for the newly discovered star may have been too weak to eject iron from its core.
The age of SMSS J031300.36-670839.3 would mean it's the oldest star ever observed, besting the current record-holder, HD 140283. Recently, researchers determined HD 140283, known as the Methuselah star, was 14.5 billion years old, based on new Hubble observations. That would make the star older than the universe itself, although there is a plus or minus threshold of 800 million years, which would mean HD 140283 would be 13.7 billion years old. A further analysis has the star's age around 13.2 billion years.
Findings of the study were published in the online journal Nature.
