Astronomy Buff

Six Ways Life on Earth Can Be Destroyed by a Nearby Supernova

by Tony on June 22nd, 2007

Having just written this post on Eta Carinae and the possibility of that explosion, some 7,500 light years distant, destroying all life on Earth, I became inspired to write a bit more about this topic.

I should mention that 7,500 light years is a bit far for a supernova to affect us, but under the right conditions, it could do it. Some theories put the outer limit to be somewhere around 3,300 light years for a supernova to have any meaningful impact on life on Earth.

There are about six ways in which life on Earth could be affected by an exploding star:

1. Gamma Radiation
2. X-rays from the explosion
3. X-Rays from the supernova remnant
4. Energetic Particles
5. Neutrinos
6. Optical, near-infrared and near-ultraviolet

According to this interesting analysis, the most dangerous sources of radiation to life on Earth come from (1) and (2) above.

So, how likely is this to happen?

Well, in the case of (1), the gamma radiation will come in the form of jets oriented in a bipolar pattern so they are highly directional. Given that there are only several hundred supernovae per year within the Milky Way and that they must lie within a certain radius to affect us, now add that the supernova’s gamma ray jets must be pointed towards us, make the chances of all life on Earth being wiped out by this very remote.

Case (2) is more likely in the sense that the X-rays will emit from the supernova in all directions, so our chances are greater there, but we still have to contend with the fact that there are so few per year (relatively speaking) and they must be within a radius from us ranging from 30 - 3,300 light years, with the closer ones being more dangerous than the farther ones.

How few is ’so few’? There’s only several hundred per year in the entire Milky Way. Of those, most are far, far away and will do nothing to the Earth, so the ones we need to worry about are the close ones. If we look at the lower limit provided by many theories as to how far away a supernova needs to be to kill us, somewhere around 10 parsecs, then there will be a supernova every 100 million - 10 billion years that could give us all a bad day.

Whew.

But don’t get too comfy in that chair. There are many stars relatively close by that are ready to blow and could affect us. Betelguese, the red giant star in the upper left armpit or Orion may blow up within the next thousand years or so, causing us to all wish we had better life insurance policies (not that there would be any agents around to file a claim to, but I digress).

Remember when killer bees were scary?

Photo credit: Chase Warnick

Technorati Tags: eta carinae, lifecycles of stars, supernova, supernova effects on earth

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POSTED IN: general astronomy, stars