Gamma Ray Bursts

But is it an existential threat?

If you’re the anxious type, maybe you’re best not reading this…

Image: NASA

One of my favourite podcasters is John Green, who is known for his anxieties. He’s able to list and discuss the top 10 existential threats for humans. The other day he talked about one I hadn’t heard of before.

A Gamma Ray Burst is (we think) the biggest bang in the universe. It takes the form of a focused blast of gamma rays, which are especially high energy particles. Humans only discovered GRBs when the US launched a satellite in the 1960s to monitor for Soviet nuclear tests.

There are two types of GRB, neither one of which you’d like to be near, and both of which result in the creation of a black hole.

The collapse of a huge star during a supernova can cause a “long” burst, of “up to a minute”. In this minute, the energy blasted into space is – get this – roughly the same as the energy our sun gives off in its entire lifetime.

In January last year, NASA detected a particularly energetic long burst. It came from a galaxy 4.5 billion light years away. It's incredible that it's even detectable at all.

The merging of two neutron stars can cause a short GRB. This type lasts only around a second, but the gamma rays produced are just as scary.

These gamma rays are focused by the magnetic forces around the dying star and squirted out along its poles of rotation. They stay compact and focused. Thankfully, also because of this focusing, you have to be in precisely the wrong place to be affected by it.

The chances of our being hit are infinitesimal.

If the Earth were hit by a GRB from a nearby supernova, the side of the planet facing the burst would be fried pretty much instantly. Nice. The rest of the planet would also be fried, only a bit slower. The burst would have disrupted the planet’s ozone layer sufficiently for natural solar radiation to destroy all life over the next few months.

What a delight. Remember, the chances of this are infinitesimal!