What’s the deadliest part of a supernova explosion?
To estimate this we have to look at what the actual destructive capabilities are of a supernova.
As in, what does a supernova produce? And how deadly are those products and what is their range?
So let’s do a quick survey.
First off, there’s the shock wave from the explosion itself.
You have a large chunk of a dead star accelerating away from it and reaching a healthy fraction of the speed of light. And that is going to slam into you, and that’s going to be really, really bad.
But trust me, if you’re close enough to a supernova to be worried about the shock wave, then you’re close enough to the pre-supernova star to get a lethal dose of radiation, and you really should have moved away a long time ago.
Next, there’s visible light, which while impressive and may lead to temporary – or permanent – blindness, it just isn’t going to be a factor.
Now you might imagine some fanciful scenario where the volume and intensity of radiation is so much that, I don’t know, it just rips the skin off of you like some category 47 hurricane But considering that visible light never accounts for more than 1% of the energy output of a supernova, I’m going to go ahead and call this a non-issue at any reasonable interstellar distance. Visible light is not a problem.
By far most of the energy emitted by a supernova is in the form of neutrinos. You know, those ghostly particles that hardly ever interact with matter.
In fact, there are trillions of neutrinos passing through your body every single second, and I bet you didn’t even notice them. Across your entire lifetime you’re going to interact with roughly one of them.
So even if you got a face full of a supernova’s worth of neutrinos, it’s not going to bother you. At interstellar distances, the neutrinos are not a problem.
Well, what about other wavelengths of light like x-rays and gamma rays? The good thing here is that supernovae tend not to produce copious amounts of high energy radiation. But the bad thing is that’s only in a relative sense.
Relative to the other kinds of radiation, there’s not an exceptional amount of X rays and gamma rays. But on any reasonable absolute scale if I’m just trying to count the raw photons, it’s still a ton of high energy radiation. So we’re going to have to keep track of that.
And lastly, we have to contend with the cosmic rays, which are not rays at all. We’re talking protons, helium nuclei, sometimes other nuclei.
They’ll just be hanging out, minding their own business, and then boom, they get this massive energy injection from the supernova, and then they go flying out like crazy.
The universe is absolutely soaked in cosmic rays. Our magnetic field and our atmosphere protect us from most of the cosmic rays, but still, if you’re standing around on the surface of the Earth, about one cosmic ray passes through you every single second, which honestly is uncomfortable if you think about it for too long.
They can also cause some ionization damage within a cell, and they’re just kind of bad news. Somewhere around 3% of all cancers on Earth are triggered by cosmic rays.
So there you have it: even though they only carry away a small fraction of the total energy output of a supernova, you have to watch out for the X-rays and the cosmic rays.
Written by Paul Sutter/Universe Today.
