A global extinction event about 359 million years ago could have been delayed by killing a distant star, a new study suggests.
Towards the end of the Devonian period (416 million to 358 million years ago) there was a mass extinction known as the Hangenberg Event; the extinct fish called plaque coderms and killed about 70% of the earth’s invertebrate species. But scientists have long envied what caused the die-off.
Recently, preserved plant spores provide clues about these ancient extinctions. Fossil tracks spanning thousands of years across the border of the Devonian and the Carboniferous showed signs of damage by ultraviolet (UV) light. These findings suggest that a cataclysmic event caused a prolonged disruption of the Earth’s ozone layer, which protects the planet from harmful UV rays. Scientists suggested that a likely candidate for this explosion of UV light could be one or more supernovae that exploded from Earth within 65 light-years, according to a new study.
Related: Wipeout: The most mysterious extinction in history
Climate change and extreme volcanic activity could also damage the ozone layer, but evidence in the geological record at the end of the Devonian could not clearly link the ozone depletion to a global disaster that occurred on Earth, the study’s authors reported.
As stars die, they emit rays of UV light X-rays a gamma ray. When a supernova is close to Earth, these rays can shatter the ozone layer, which can damage the Earth’s unfiltered UV light from the sun and damage life on the planet’s surface. However, this damage is typically short lived. The effects disappear after a year as such, “and after a decade, Earth restores its ozone,” said lead author Brian Leads, a professor of astronomy at the University of Illinois at Urbana-Champaign.
But that initial bombing is just the first stage of damage a neighboring supernova could inflict, Fields Live Science said in an email.
“Later, the supernova explosion kicks in solar system. The explosion acts as a particle accelerator, and the Earth is bathed in an intense rain of high-energy particles, “known as muons,” Fields said. “Not only does this explosion radiate away the earth’s ozone layer – moons then irradiate the earth’s surface and penetrate deep below the ground and into the oceans.
“These will damage life, and the cosmic rays will last for thousands of years, up to 100,000 years,” Fields said. If a supernova – or more than one – contaminated Earth’s ozone layer, that could explain the UV damage found in Late Devonian traces and pollen over millennia, the researchers reported.
Light years away
How close must a star be before its death to affect Earth?
“Work by my co-authors and others has shown that a supernova about 25 light-years away would lead to biological cataclysm – a true mass extinction,” Fields said. “For context, the nearest star is 4 light-years away today,” he added. Because the extinction of Hangenberg was less severe than other mass extinctions in Earth’s history, the study authors estimate that the Devonian supernova exploded about 65 light-years away (although, there is no potential yet). candidate for a star in this range that died 359 million years ago).
The good news is that you do not have to worry about a supernova-emerging life as we know it – at least not every moment.
“I’m glad to report that no threatening supernova candidates are anywhere near the ‘minimum safe distance,'” whereupon Earth could be damaged by a supernova, Fields told Live Science.
In recent months, the attention of scientists has focused on unusual dimming in the red giant Betelgeuse, which is in its final stages of life and is expected to explode relatively quickly (in astronomical terms) in a spectacular supernova – within about 100,000 years.
Betelgeuse is about 1,000 times the size of our sun, so explosion should be quite spectacular. But at more than 642 light-years from Earth, “it is far enough away that the fireworks will be harmless to us,” Fields said.
The findings were published online in the journal on August 18 Procedures of the National Academy of Sciences.
Originally published on Live Science.
