How dangerous is a kilonova for us?

Kilonovae are bright flashes that occur when two neutron stars merge. The high-energy radiation that is born as a result of them can potentially kill life on Earth. But for this to happen, the catastrophe must happen very close to us.

Kilonova explosion. Source: NOIRLab/NSF/AURA/J. da Silva/Spaceengine

Space hazards

A group of researchers has published an article that is devoted to research on the risks to the Earth from kilonovae. These extremely powerful flares occur when two neutron stars collide. The latter are extremely dense remnants of ordinary luminaries that once exploded as supernovae.

There are generally enough high-energy events in space that can potentially pose a danger to the Earth if they happen somewhere nearby: supernovae, mergers of black holes, and tidal destruction. We are able to see them through the entire Universe, which means that at a distance of several world years they can “fry” our planet.

However, the Earth is also not defenseless. Its atmosphere and magnetic field are able to effectively disperse and absorb a significant part of the particles. And the energy density from a powerful flare drops proportionally to the square of the distance to it.

Therefore, for example, scientists are not very worried about supernovae. The closest star to us is Betelgeuse, which in the next few millennia may turn into it. And it is as much as 600 light-years away, so in the event of an explosion, it will only turn into a star for tens of weeks, the brightness of which in our sky will be commensurate with the Moon.

How dangerous are kilonovae

But no one has estimated how dangerous the kilonovae are so far. Therefore, scientists decided to find out at what distance its high-energy rays from it would be too strong for the atmosphere and the magnetic field to protect from it.

Researchers have identified three main factors in the kilonova explosion that can cause problems on Earth. The first is X-ray radiation, which comes from the polar regions of neutron stars. It turns out to be dangerous at a distance of up to 16 light-years, because it scatters well.

The second factor is the flare, which mainly originates from the equatorial regions of colliding stars. It is gamma radiation, which dissipates even better, so it is dangerous for the Earth at distances up to 13 light years.

With the third factor, everything is much more complicated. This is a shock wave, a gas front that expands in space. Unlike the first two factors, which propagate at the speed of light, this danger moves much slower. It is capable of reaching our planet thousands, or even tens of thousands, of years after the explosion. It is dangerous at the same time, at a distance of up to 36 light years.

However, all these figures are very small on a cosmic scale. Kilonovae are not found in space so often that we have met with any of them. Therefore, the danger from these phenomena to the Earth is minimal.

According to

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