Most of us are killed after receiving
a large dose of gamma rays. For a select few,
the exposure can unleash our inner demons.
Image courtesy of
Continuing on the theme of Supernovae from my last posting, I’ll take this opportunity to address an earlier question that was asked by one of my loyal readers: “Perhaps your thoughts on the controversial topic of the effect of Gamma Rays on humans?”
Being a Berkeleyite and working at the home (www.lbl.gov) of the Gammasphere, I can’t help thinking of the Incredible Hulk when I read this question. In Marvel Comics, the Incredible Hulk was born when a brilliant but emotionally repressed Berkeley Physicist was exposed to an enormous dose of gamma radiation from his failed experiment. The genetic mutations from the exposure released his dark, hidden emotions in the persona of a savage dark green monster – a superhero with little wit or self-control.
Like visible light, gamma radiation is carried by photons. However, each photon in the gamma region of the electromagnetic spectrum has millions of times more energy than a red or blue photon that we see with our eyes. With so much energy, a gamma photon is capable of doing great damage by knocking the electrons around in living tissue like a pinball machine.
The Veil supernova remnant.Credit: J. J. Hester (Arizona State University),
WFPC, HST, NASA*
The largest source of gamma radiation is believed to be short, but intense gamma ray bursts. We are unsure of the exact nature of gamma ray bursts, but we suspect they may be the associated with supernovae. The intensity of a gamma ray burst implies that some energy from a supernova blast is focused like a laser beam. If this assumption is correct, then only a small fraction of supernova blasts will direct that beam of gamma rays at Earth.
All gamma ray bursts that have been detected are well outside our galaxy, often billions of light years away. For a supernova or gamma ray burst to do any damage, it has to be well within the Milky Way. For more information on X-ray and gamma ray exposure from a nearby supernova, check out some rough calculations.
We are fortunate that supernova blasts are rare, occurring once every few hundred years in the Milky Way. Gamma ray blasts in the Milky Way are much rarer. Some scientists suspect that there may have been at most a few such explosions in the Earth’s four billion-year history. If so, it’s only a matter of time before we get hit again. I know it’s not particularly good news, but at least we know the Hulk will rise again.
Kyle S. Dawson is engaged in post-doctorate studies of distant supernovae and development of a proposed space-based telescope at Lawrence Berkeley National Laboratory.
* Remains of a supernova located 2600 light years away. This supernova is believed to have exploded about 15,000 years ago and should not have posed any threats to a human population that was patiently awaiting the end of the most recent ice age.