At 13.7 billion years old, the universe is inconceivably ancient. As new stars are born every day, its cosmic inhabitants are constantly changing, but scientists have now discovered the oldest star existing in space.
The old timer was identified by a team of astronomers from The Australian National University, who believe it formed shortly after the" Big Bang" that spawned the cosmos 13.7 billion years ago.
The newly-observed star, christened SMSS J031300.36-670839.3,has just topped the age of the current record holder, HD 140283 or "The Methuselah Star," which has been dated to be 13.2 billion years old.
Stars are known to be incredibly long-lived, with some of the smaller, more "fuel-efficient" stars capable of living for 15 billion years, longer than the universe itself. By comparison, our own sun, an average-sized star, is about five billion years old and is predicted to keep burning for another five billion years. The longevity of a star depends on the amount of fuel it has; their brilliant and volatile existence is created by the nuclear fusion of hydrogen into helium at their core, where temperatures can reach up to 20 million degrees. Larger, heavier stars tend to burn up their fuel more rapidly, and consequently shine with a brighter intensity.
"To make a star like our Sun, you take the basic ingredients of hydrogen and helium from the Big Bang and add an enormous amount of iron – the equivalent of about 1,000 times the Earth’s mass," said one of the lead researchers, Dr. Stefan Keller of the ANU Research School of Astronomy and Astrophysics."To make this ancient star, you need no more than an Australia-sized asteroid of iron and lots of carbon. It’s a very different recipe that tells us a lot about the nature of the first stars and how they died."
The team, led by Stefan Keller and David Paterson, found the new star using the ANU SkyMapper telescope at the Siding Spring Observatory, and its composition indicates that it formed in the wake of a primordial star which had a mass 60 times that of our Sun. Scientists will now be able to study the chemistry of the earliest stars and gain an insight into the nursery stages of the universe.
"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 Dr. Keller.
It was previously thought that the explosive deaths of primordial stars polluted huge areas of space with iron, but the newly-discovered star has no iron content, and is instead contaminated with lighter elements including carbon and magnesium. The low iron content gives new insights into the formation of the first stars and galaxies.
"This indicates the primordial star’s supernova explosion was of surprisingly low energy. Although sufficient to disintegrate the primordial star, almost all of the heavy elements such as iron, were consumed by a black hole that formed at the heart of the explosion," he explained.
The Sky Mapper, which photographed images of 60 million stars in its first year, is part of a five year project to scan the universe and produce the first digital map of the southern sky.
"The stars we are finding number one in a million," said team member Professor Mike Bessell. "Finding such needles in a haystack is possible thanks to the ANU SkyMapper telescope that is unique in its ability to find stars with low iron from their colour."
The ancient star is a fairly close neighbour to Earth at around 6000 light years away. Its discovery, published in the journal Nature, was confirmed by Dr. Keller and Professor Bessell via the Magellan telescope in Chile.
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