Around 13 billion years ago a star died a violent death in a massive explosion that was much more powerful than a supernova.
Key points:
- Astronomers have found a star in the Milky Way that was born shortly after the Big Bang
- The star's unusual chemical makeup suggests that it was formed by the explosion of a massive fast-spinning star with a strong magnetic field
- The findings may answer questions about where some of the heavier elements in the universe came from
Evidence of this cataclysmic event, known as a hypernova, is in the chemical pattern of a newly discovered star, which has elements that could only have been created by such a huge explosion.
The discovery, reported today in the journal Nature, could help solve a mystery that has puzzled scientists for 40 years.
"We've never seen this particular pattern in a star before," said study co-author David Yong, an astronomer at the Australian National University.
Discovering a mysterious star
Dr Yong and colleagues discovered the star located 7,500 light years away while searching for ancient stars using the SkyMapper telescope at Siding Spring Observatory in New South Wales.
They
confirmed the observation using the Australian National
University's 2.3-metre Telescope and the European Southern Observatory's
8-metre Very Large Telescope in Chile.
Dubbed, SMSS J200322.54-114203.3, the star had a had an iron-to-hydrogen ratio around 3,000 times lower than the Sun, suggesting it formed around 13 billion years ago.
But the star also had very high levels of heavier elements then iron such as zinc, uranium, europium and possibly gold.
This combination of elements makes it extremely unusual for stars of its age.
The universe was a relatively sparse place in its infancy when this star formed just after the Big Bang 13.8 billion years ago.
The earliest stars were mostly made up of just two elements: hydrogen and helium, which are still the most common elements in the universe.
When these first massive stars exploded and collapsed, heavier elements such as carbon, oxygen and iron were created and flung out into the universe to seed the next generation of stars.
But one of the biggest mysteries of astronomy has been where did all the elements heavier than iron come from, said Stuart Ryder, an astronomer at Macquarie University who was not involved in the study.
"We know they were not created in the Big Bang, nor were they simply 'cooked up' inside stars by the fusion of lighter elements," Dr Ryder said.
First evidence hypernova may have happened
Heavier elements were thought to be generated by the dead cores of massive stars, known as neutron stars, smashing together.
In 2017, scientists caught a glimpse of this process through the detection of gravitational waves produced by the collision.
But the chemical pattern of the newly discovered star doesn't match those that are generated by neutron star mergers, Dr Ryder said.
For instance, the star's unusually high levels of nitrogen likely resulted from a fast-spinning object, while an abundance of zinc suggests a huge explosion occurred.
The only explanation that fits is that the star got its unique chemical pattern from the destruction of a massive, whirling star called a magneto-rotational hypernova.
While scientists have suspected these hypernovae existed, they hadn't been able to track down any evidence of them, Dr Yong said.
"These objects have been theorised, but they've never been observed.
"Now we have for the first time evidence that these objects may have existed in the early universe."
Building a picture of the first stars
Fiona Panther, an astrophysicist at the University of Western Australia not involved in the discovery, said that the findings expand our understanding of stars in the early universe.
"They may have had much stronger magnetic fields and rotated faster than stars today."
But while the discovery offers another explanation for where heavy elements came from, more work was needed to confirm if they are indeed produced by hypernovae, Dr Panther added.
"To confirm this theory, we would need to observe these explosions directly - likely by looking for the flashes of gamma-rays they are thought to produce," Dr Panther said.
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