Imagine taking a Supernova and converting it into the deadliest cosmic sniper capable of eradicating Solar systems, though a gross oversimplification, that’s basically what Gamma Ray Bursts (GRB’s) are. They are rays of gamma particles (or waves) that last for varying durations, in terms of seconds to minutes. Gamma rays are incredibly powerful. A single gamma ray photon is more energetic than a million visible photons combined. This high energy makes gamma rays a form of ionizing radiation, meaning they are capable enough to break apart atomic bonds, which makes it dangerous to humans as they can destroy the delicate bio-machinery that keeps us live. Fortunately the ozone layer protects us from them. Now, if the ozone layer blocks us from gamma rays, how were they detected in the first place?
These were the one positive outcome that had come as a result of the cold war, when the US spy satellites were launched in space to detect gamma rays from possible nuclear tests being conducted by the Soviet Union in space. These satellites did pick up signals though not from earth, but from Galaxies billions of light years away, which were GRB’s. These lasted only for a few seconds.
They were a mystery for 30 years, but eventually we discovered a source for the GRB from a Galaxy 6 billion light years away. If a GRB can be seen from such a distance, it must be incredibly energetic, releasing more energy in a second than the Sun will in its entire lifetime, making GRB’s the brightest events in the Universe.
Now, where do they come from? There are two types of GRBs, short and long, and each has their own source. The long GRBs last typically for a minute and are the result of a dying Supernova which ends up giving birth to a Black Hole. A short GRB last a few seconds and occur when two neutron stars in a binary merge and yet again are forming a Black Hole. These Black Holes are surrounded by a magnetic disk of gases and particles of their parent stars. In such an environment where the rotation winds up the magnetic fields, which in turn funnels hot jets of particles at the speed of light. The gas jets out two tight rays of gamma radiation. These, contrary to most other cosmic events which are more spread out and fade away, are focused and can be seen from much further.
On an average we detect one per day, thankfully most are harmless. Most GRB’s detected have originated too far away, thus making it hard for the rays to reach Earth, but a close enough GRB, occurring a few thousand light years away would be fatal. One from a few light years away would just cook the surface of the Earth. The former scenario is suggested to have already happened, 450 million years ago. As a possible explanation for the Ordovician extinction which eradicated almost all marine life forms. Although it is pretty much impossible to prove this.
On a positive note, though highly unlikely, if a GRB is to occur close to Earth, we won’t know its headed our way till it arrives. So, there could already be a GRB headed towards Earth and we won’t know it until it hits us and we’re all dead. Have a nice day 🙂