There are a lot of very excited astronomers about today with the possible detection of a gamma-ray burst (GRB) in the closest galaxy to us, Andromeda (known under the Messier catalogue designation ‘M31’). GRBs have been detected before, but never this close (Andromeda is ‘just’ 2.5million light years away). It’s thought that the explosion has likely been caused by two colliding neutron stars (another possibility is a supernova, but the stars in that area are not thought to be large enough to nova).
But what are GRBs, and should we be concerned? After all, what happened to Bruce Banner actually paints GRBs in a *good light*…
Gamma rays are blamed for making Bruce Banner the Incredible Hulk. But what are gamma rays and what can they really do?
Gamma rays are the highest energy form of light. The rainbow of visible light that we are most familiar with is just part of a far broader spectrum of light, the electromagnetic spectrum. Past the red end of the rainbow, where wavelengths get longer, are infrared rays, microwaves and radio waves, while beyond violet lie the shorter wavelengths of ultraviolet rays, X-rays and, finally, gamma rays.
A gamma ray packs at least 10,000 times more energy than a visible light ray. Unlike the Incredible Hulk, gamma rays are not green — lying as they do beyond the visible spectrum, gamma rays have no color at all that we can describe.
Exactly how Bruce Banner survives his transformation is unclear. Just as high doses of X-rays are typically lethal, so too would an explosion of gamma rays kill the average person.
Gamma rays can knock electrons around like a bowling ball would bowling pins. These charged particles can then disrupt any chemical bond they come across, wreaking havoc on the delicate chemical machinery of the cell and generating molecular fragments that can act as toxins.
To put it gently, a gamma bomb in the real world would not turn Bruce Banner into the Incredible Hulk. Rather, it would likely quickly turn him into a corpse dead from radiation sickness, if not incinerating him instantly.
In short: if a GRB hit us hard, it would kill all life on planet Earth. Gulp. Doesn’t sound too good does it? Fortunately, GRBs are highly directional, and this one wasn’t pointing at us (and additionally, even the galaxy next door is still a long distance away from us). As astronomer Robert Rutledge responded to a concerned person on social media, the basic rule of thumb with GRBs is “if you can get to the end of the sentence, ‘Hey, what’s going on?’ You’re gonna be fine”.
Astronomers are awaiting detection of neutrinos here on Earth to confirm the event as a GRB – another possibility is that it is an ultra-luminous X-ray source (ULX) – it’s still very early days (it was only detected a couple of hours before the writing of this post). The Heavy Metallicity blog is one of the first reporting this in layman’s terms (as opposed to the more science-directed releases), and will be updated as more is known, so keep an eye on it and the Twitter hashtag #GRBm31 for new developments over time.