The Likelihood of Mass Extinctions from Space

There are lots of scary YouTube videos claiming the end of the world could be caused by an astronomical event. But how likely is such an astronomical event to occur?

So, let us examine the most common scenarios and order them by most likely to least likely to happen to see if the scary predictions are worth the hype.

Number Five - Rogue Black Hole

A rogue black hole or stellar black hole is a black hole formed by the gravitational collapse of a star.

The black holes have masses ranging from about 5 to several tens of solar masses and a diameter of around 300 kilometres.

What makes this type of black hole dangerous is that they can drift through space. These are not theoretical; a rogue black hole was located just 1000 light years away in the Telescopium constellation.

If a stellar black hole managed to get into our solar system, it could dislodge objects in the Oort cloud sending them Earthwards in the form of comets.

If it got within the orbit of Neptune, it would knock the planets out of their orbits causing the potential complete destruction of the Earth.

However, the chance of a Rogue Black Hole approaching close enough to us to cause a mass extinction event is astronomically small due to the sizes and rarity of the objects involved.

Number Four - Starquake

At number four is a starquake, something that sounds like it came straight out of a sci-fi movie Starquakes occur on magnetars, which is a type of neutron star.

In a similar way to how earthquakes occur on the Earth, the crust of a magnetar can undergo a sudden adjustment, this can release a massive Gamma Ray Burst along with a very powerful magnetic field.

That if the Earth were close enough could result in a mass extinction event. There is some evidence that in binary neutron star systems the resonance between the crust and the tidal forces of the rotating stars can potentially cause starquakes.

However, starquakes are rare events with only three recorded in the last fifty years all of which were located very far away.

The chance of this event happening close enough to us to cause a mass extinction event soon is practically zero due to us knowing the positions of the nearby neutron stars capable of star quaking.

None of which are close enough for enough radiation to cause a mass extinction event.

Number Three - Supernova

This can occur when massive stars many times the size of our sun explode at the end of their lives.

If a supernova explodes less than 10 parsecs or 33 light years away it would lead to major effects on the Earth, X-rays and more energetic gamma-rays from the supernova could destroy the ozone layer that protects us from solar ultraviolet rays.

It also could ionize nitrogen and oxygen in the atmosphere, leading to the formation of

large amounts of smog-like nitrous oxide in the atmosphere.

All of which could lead to mass extinctions.

In fact, Gamma Ray Bursts can release more energy in 10 seconds than our Sun will in its entire life. The current theory is that these bursts occur during a supernova or super luminous supernova, when as a high-mass star implodes to form a neutron star or a black hole. One such event occurred during the 8th century at a distance at 3000 to 12,000 light years away.

Fortunately, our atmosphere absorbed the blast leaving just trace isotopes on the surface. If the same burst happened now, it would still knock out our satellite network.

Estimates predict that a supernova explosion will occur once every 240 million years at a close enough distance to eliminate life on Earth.

Number Two - Asteroid or Comet Impact

This is only at number two, due to its rarity. However, an impact of just a 10km wide asteroid would be sufficient to destroy all life on Earth.

But smaller asteroids could still do significant damage.

The NEOWISE project found that there are approximately 4,700 asteroids that could do significant damage to the Earth.

While a giant asteroid crashing into our planet would instantly kill off millions of humans and animals.

The aftermath of such an impact would be even more disastrous with Tsunamis, earthquakes, and huge clouds of dust blocking out the Sun leading to crop failure and mass extinction.

An asteroid impact large enough to end life on earth occurs approximately every 20 million years.

Number One - Superflare

Superflares happen when stars, for reasons that scientists still do not understand, eject huge bursts of energy visible hundreds of light years away.

While the Earth's magnetic field and atmosphere would absorb most of this power. It would still disrupt electronics across the globe, causing widespread blackouts and knocking out communication satellites in orbit causing severe problems for our civilization.

Perhaps more dangerously it could deplete our ozone layer leading to more skin cancer and cataracts.

One of these events should occur every 10,000 years or so and is the most likely space borne disaster, however it is also the least destructive of the five events we have discussed.

The odds are even very low for Superflares, Asteroid and Comet Impacts, however in my opinion it is still worthwhile to try and detect these events and mitigate their effects. As we now have the technology to do so.

If you would like to see some visuals of these events please watch the episode below.