There are chances of a supernova triggering a mass extinction event and it might have happened in the pastNASA/CXC/SAO/R.Margutti et al

The planet right now is going through its sixth mass extinction event and this one can be blamed on human activity, but previous events that wiped out a large part of Earth's life can be traced back to supernovae from nearby stars dying out.

"We are interested in how exploding stars affect life on Earth, and it turns out a few million years ago there were changes in the things that were living at the time," astrophysicist Brian Thomas from Washburn University in Kansas told Astrobiology Magazine.

"It might have been connected to this supernova," he says.

For this research, Thomas and his team investigated a supernova which took place between 2.5 and 8 million years ago at a distance of over 160 light years from Earth. While that might not seem close enough to be dangerous, supernovae are so large that cosmic fallout could be deadly even at this range.

The team studied what the kill zone of a supernova would be like and found that the wave of radiation from a star dying is not a quick one time burst of particles, reports Science Alert. It is something that slowly goes on and on for a few hundred if not thousands of years. Death will come as a result of the radioactive transfer, with the radiation levels peaking about 300 years into the event.

Radiation from a supernova could eat away the upper protective layers in the atmosphere, including the planet's ozone, altering life and chances of survival here on the planet.

Without the protection provided by the ozone layer, the Sun's UV radiation reaching Earth's surface could cause the death of most plants and trees over time. Given enough time, the strong radiations could cause cancer and even alter the DNA.

With the ozone gone, the radiation could be slowly killing off and damaging most prospects of survival, notes the report.

Earth's fossil record actually indicates towards such an event having occurred about 2.5 million years ago. "There were changes, especially in Africa, which went from being more forested to more grassland," said Thomas.

While there is no definitive way to prove that this did happen, Thomas said that Earth did feel it in some way, "There is a subtler shift," Thomas said. "Instead of a 'wipe-out everything', some [organisms] are better off and some are worse off."

What is a supernova?

When a star dies, two things are likely to happen based on its size and the energy it has contained within itself. They can either collapse into themselves and become black dwarves if they are small, like the Sun in the middle of the Solar System.

Large stars with a lot of fuel expand and then explode - this event is a supernova. After a supernova, a star can either turn into a black hole if it is big enough, or they become dense neutron stars, according to the ESA.

A Supernova is the largest explosion that takes place in the universe. During the explosion, a massive amount of various gasses, radiation and matter is spewed into space. NASA explains that these explosions are responsible for the scattering of many different elements into deep space. They are responsible for the formation of planets, and sometimes, some material could even reach Earth.