Basic Astronomy

Oldest known star in the Universe is discovered by Australian astronomers

12nd February 2014: A team from Australian National University (ANU) discovered a star which is the oldest known star in the Universe. The discovery made with the Sky Mapper telescope at the Siding Spring Observatory near Coonabarabran. This discovery should revolutionize human understanding of beginning and evolution of this Universe following the Big Bang.

Oldest star, SMSS J 031300.36-670839.3
(The oldest star discovered by a team led by Dr. Stefan Keller with the SkyMapper telescope. Picture credit: Space Telescope Science Institute)

The newly discovered star is about 13.6 billion years old and located around 6,000 light years away from Earth. This means it was formed just a few million years after the Big Bang, thought to have occurred some 13.8 billion years ago.

The star is discovered within our own Galaxy. The principle investigator of the discovery team, Dr Stefan Keller, describe the discovery as a "one in a 60 million chance."

Keller told Reuters, "It's giving us insight into our fundamental place in the universe. What we're seeing is the origin of where all the material around us that we need to survive came from,". He further added, "This is the first time we've unambiguously been able to say we've got material from the first generation of stars," said Keller. "We're now going to be able to put that piece of the jigsaw puzzle in its right place."

The star got catalogue reference of SMSS J 031300.36-670839.3. It is believed to be formed in the wake of a primordial supernova. The age of the star was determined from an analysis of its iron content.

(The Sky Mapper project (picture credit: Jamie Gilbert).)

Mystery of missing Lithium

There were nothing in Universe after Big Bang except hydrogen, helium and trace amounts of lithium. All heavy elements we see today (including iron) were forged in stars and supernovae. 'Modern' stars are created from the matter ejected from multiple star explosions and contain many different elements. Composition of older stars are much more simplistic.

"The iron level of the Universe increases with time as successive generations of stars form and die," explained Keller to AFP. "We can use the iron abundance of a star as a qualitative 'clock' telling us when the star was formed."

"In the case of the star we have announced, the amount of iron present is less than one millionth that of the Sun and a factor of at least 60 times less than any other known star. This indicates that our star is the most ancient yet found", added Keller.

Presence of extremely low iron in SMSS J 031300.36-670839.3 suggests that the star was formed with an explosion with relatively low energy. This is an unexpected finding which suggests that early supernovae were much more varied in their energy than previously thought.

This low-energy supernova might help scientists understand one of the discrepancies between present model of the Big Bang and observations of the Universe - especially the scarcity of the element lithium.

Speaking to The Register, Dr Keller told that lithium (Li) was created during the Big Bang but most of it was vanished over time by the nuclear reactions occurring in stars. However, the amount of lithium in the Universe do not matches with the present Big Bang and cosmology model and these is a hole in current understanding on this matter.

spectrum of oldest star, SMSS J 031300.36-670839.3
(Spectrum of the oldest star SMSS J 031300.36-670839.3, posted to Twitter by Anna Frebel, MIT who is part of the discovery team.)

This latest evidence of low-energy supernovae gives a clue to solve this lithium paradox. Presence of less iron in the newly discovered star suggests that early stars were massive and burned more lithium than previously thought.

"They burn the lithium, then they blow up, and don't emit much iron," explained Keller. "This helps us bring the lithium abundance into line with what the Big Bang theory predicts."

This new discovery was published in the latest edition of the well known science journal Nature.

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