Astronomers were concerned last year when a supergiant star visible to the naked eye from Earth began darkening amid concerns it might explode.
Such an explosion could cause severe damage to life on Earth if it were close enough.
But as Betelgeuse returned to normal, researchers found evidence that the Earth was destroyed by another star that exploded 2.5 million years ago.
It may also have triggered an ice age, the researchers believe.
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When stars more than ten times larger than our sun die, they explode in a supernova, a vast explosion.
The explosions lead to the formation of heavy elements found on Earth, including iron and manganese.
Researchers from the Technical University of Munich (TUM) analyzed layers of a manganese crust that were about two and a half million years old.
The researchers found both iron-60 and manganese-53
Dr Gunther Korschinek said: “The increase in manganese-53 concentrations can be regarded as the ‘smoking gun’, definitive proof that this supernova really happened.”
Researchers say that while the supernova was too far away to harm life on Earth, it caused an increase in cosmic rays for thousands of years.
In turn, this may have triggered an ice age.
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The co-author, Dr. Thomas Faestermann, says: “This can lead to more cloud formation”,
“Perhaps there is a connection with the Pleistocene epoch, the period of the ice ages, which began 2.6 million years ago.”
Typically, manganese is found on Earth as manganese-55. Manganese-53, on the other hand, usually comes from cosmic dust, such as that found in the asteroid belt of our solar system.
New sediment layers that accumulate year after year on the seabed preserve the distribution of elements in manganese crusts and sediment samples.
Using accelerator mass spectrometry, the team of scientists have now detected both iron-60 and rising manganese-53 levels in the layers that were deposited about two and a half million years ago.
“This is ultra-trace investigative analysis,” says Korschinek. “We’re just talking about a few atoms here. But the accelerator’s mass spectrometry is so sensitive that it even allows us to calculate from our measurements that the star that exploded must have been 11 to 25 times the size of the sun.”
WATCH: Supernova captured in a time-lapse video