Kilonovas: Ultra rare cataclysmic collision could eradicate all life on Earth, study finds

A collision between two decaying stars in the Milky Way galaxy could eliminate the Earth's ozone layer, and indue a mass extinction of all life on this planet, a new study has suggested, with researchers say the collision is a potential ultra-rare cataclysmic event. 

Scientists from the University of Illinois Urbana-Champaign in the US say such an event could pose dangers to all life on Earth, even though until now, astronomers have observed only a handful of such neutron star collision events known as kilonovas.

Radiation produced from the star collisions is the biggest threat, which includes gamma rays and the X-ray afterglow they produce.

“Ionizing radiation from these sources can be dangerous for life on Earth-like planets when located too close,” researchers wrote in the study.

The yet-to-be peer-reviewed research, posted in the arXiv preprint server, could help determine the chances of life surviving on other worlds in proximity to these star collision events, which was calculated on an analysis of what we know from the first-ever neutron star collision detected – a stellar event named GW170817.

If a blast happened in the Milky Way galaxy, and the Earth was in a narrow range of about 297 light-years (97 parsecs) of such an explosion, it could get burned by powerful gamma radiation and remove the Earth’s stratospheric ozone, which may take a handful of years to recover.

The life-destroying X-ray afterglow would be around 16 light years away. The scientists said: "For baseline kilonova parameters, we find that the X-ray emission from the afterglow may be lethal out to ∼5 pc and the off-axis gamma-ray emission may threaten a range out to ∼4 pc. The greatest threat comes years after the explosion, from the cosmic rays accelerated by the kilonova blast, which can be lethal out to distances up to ∼ 11 pc."

However, this event is dependent on the “viewing angle, ejected mass, and explosion energy”, and due to the rarity of kilonova events, researchers also said such stellar collisions are “not important threats to life on Earth”.

“The rarity of binary neutron star mergers combined with a small range of lethality means that they are probably not important threats to life on Earth. We find that the mean recurrence time of lethal mergers at the location of the Sun is much larger than the age of the Universe.

“However, even if it never induced a mass extinction, a nearby kilonova event would be visible on Earth. It would likely disrupt technology soon after the merger and remain bright in the sky for over a month,” the scientists said.