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Maybe not right now, nor maybe not even tomorrow, but it could happen. Life on Earth could be in serious jeopardy. And the enemy is not anyone or anything on this planet, but rather the workings of an enemy 5000 to 8000 light years away. The sad thing is, there may be no way to see it coming, and most certainly nothing we can do about it. There are over 300,000 gamma ray bursts a year so there is a chance that one could be directed straight towards Earth.
When an enormous star detonates into a supernova, radioactive nuclei are shot out into interstellar space releasing countless photons. This radiation tends to be very low wavelength, high frequency in the gamma ray portion of the electromagnetic spectrum.
Courtesy of http://www.antonine-education.co.uk/physics_gcse/Unit_1/Topic_5/em_spectrum.jpg
To quantify the amount of energy we can use Plank’s Law. According to Plank’s law the energy of a photon can be expressed by the following equation:
E = energy of a photon
h = Plank’s constant = 6.625 x 10-34 J*s or 4.135 x 10-15 eV*s
λ = wavelength of light
Using this equation, the photons of gamma rays will have the highest energy of all as their wavelength is exceptionally small. Thus, a gamma ray photon would produce the largest amount of energy of any type of electromagnetic radiation in the electromagnetic spectrum. While the release of one photon may seem small, the radiation from a supernova directed towards Earth may carry the energy of seemingly countless photons. The result is a tremendously high amount of energy bound for the Earth. To put the amount of energy into perspective, Dr. Edo Berger, an astrophysicist at Harvard University, the energy released by a gamma ray burst is equivalent to powering the world for 1027 years.[1]
The effects could be substantial. One scenario popularized by the History Channel’s series Mega Disasters depicts the gamma radiation attacking and destroying the ozone layer of the Earth while releasing a smog of nitrogen oxide, nitrogen dioxide, and dinitrogen trioxide compounds that effectively block the Sun, break down ozone and cause acid rain. Without the Sun’s rays, a global cooling would exist and plant life could not continue, abruptly disrupting the food chain for all on Earth. According to Dr. Derek Fox, an astrophysicist at Penn State University, a gamma ray burst could irradiate the Earth to the equivalence of 100,000 atom bombs exploding just outside of the Earth’s atmosphere.[2]
Courtesy of: http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod/image/9904/wr104_sslkeck_big.jpg
So how likely is the threat? The biggest possibility comes from WR104 that sits about 8000 light-years away. If directed perfectly at Earth, the effect on life could be devastating and the fate of the planet may be in jeopardy. But don’t get all worked up just yet. According to David Thompson, a NASA astrophysicist and deputy project director on the Fermi Gamma-ray Space Telescope, the likelihood of a gamma ray burst from WR104 is equivalent to, “the danger I might face if I found a polar bear in my closet in Bowie, Maryland. It could happen, but it is so unlikely that it is not worth worrying about.”[3]
1.http://www.astro.caltech.edu/~ejb/faq.html
2. History Channel. MEGA DISASTERS: GAMMA RAY BURST ©2007
3. http://blogs.discovermagazine.com/badastronomy/2008/03/03/wr-104-a-nearby-gamma-ray-burst/
