Friday, August 7, 2009
Electromagnetic radiation is a physical phenomenon in our universe that all of us interact with on a daily basis. The electromagnetic spectrum categorizes this radiation based on frequency. The visible light that you perceive with your eyes is only a tiny range of frequencies in this spectrum. Frequencies below visible light include infra red, microwaves, and radio/TV signals. Frequencies above visible light include ultra violet, x-rays, and gamma rays.
We know from our own experiences in the modern world that visible light is generally harmless. We evolved in a world bathed in visible light coming from our sun so it’s only natural that our eyes are specialized to respond to those frequencies. We know that infra red is mostly associated with heat. We’ve seen infra red camera footage and know that the heat lamps that keep the fries warm at the fast food place are just specialized light bulbs that radiate most of their energy at infra red wave lengths. Microwave ovens became ubiquitous in the 1980’s and work by pumping electromagnetic energy into food at a specific frequency that makes the water molecules vibrate and heat up. Below microwaves, radio and TV signals radiate from the tops of mountains and man-made towers to bring audio and video into our homes and vehicles. CB radios, baby monitors, Wi-Fi internet, Bluetooth headsets, and mobile phones all do their things down here.
Above visible light, ultra violet frequencies give us sunburn and, if we’re not careful, skin cancer. Light bulbs tuned for ultra violet (aka black lights) are used to sterilize water, instantly dry inks in printing processes, make your hippie posters fluoresce, and make the bowling pins glow during midnight madness. At even higher energies, x-rays pass through objects and allow us to see inside the human body and airport luggage. Excessive amounts of x-ray radiation can cause cancers in animals but can also be tightly focused to destroy tumors. Stars and nebulae often emit x-rays and because of their energy and their ability to pass through matter unimpeded, astronomers often use these frequencies in their research to see farther and in more detail than visible light allows.
Gamma rays are generally thought of as having higher energies than x-rays but the two classifications actually overlap quite a bit. Gamma rays have medical uses similar to x-rays and are employed in sterilization procedures similar to ultra violet. In astronomy, flashes of gamma rays from deep space were first detected accidentally in the 1960’s by cold war satellites monitoring nuclear weapon tests. These flashes were later dubbed “Gamma Ray Bursts” and seemed to originate from the explosions of dying stars.
Gamma Ray Bursts caused considerable controversy amongst astronomers and astrophysicists when they were first identified because they were simply too powerful to exist according to known physical laws. The problem was straightforward. An explosion in space radiates matter and energy in all directions more or less equally. If you detect a gamma ray burst, measure its intensity, and then swing your visible light telescopes around to the same coordinates, you typically (although not always) see the remnants of a novae -- a star that has exploded at the end of its death throes. You can then use various tricks to calculate the distance to that novae and, along with the gamma ray intensity that you measured, determine how powerful the initial explosion had to be based on how much of that energy managed to reach you. All of the gamma ray bursts were determined to be outside of our own galaxy, billions of light years away, and therefore the energy from a symmetrical explosion would have to be the equivalent of all of the energy released by a sun like ours over its entire lifetime based on the level of energy that still managed to reach us from so far away.
Observations later revealed that these calculations were based on a false premise. The gamma ray bursts were NOT symmetrical and in fact were focused into two opposing beams spreading out between 2 and 20 degrees.
If you were observing from a vantage point that was not directly within this focused beam of gamma rays, you may only see a brief flash of visible light or perhaps nothing at all. Effectively these types of novae and super novae explosions producing gamma ray bursts are happening all of the time in our observable universe but we only see them if we happen to be looking ‘down the barrel’ of the gamma ray ‘gun’. Even so, they are not of much concern to us because on average these types of explosions only happen in each galaxy every 100,000 to 1,000,000 years.
Then there’s this thing:
WR104 is a massive star in the constellation of Sagittarius and is in its death throes, ejecting massive amounts of plasma and debris as it tries to balance its crushing mass with its internal fusion processes. It has an O-type binary companion star, and the interactions of their gravity fields produce the swirling pattern that you see in the image above.
Which is eerily reminiscent of the image below:
Yep, you guess it. We’re looking right down the gun barrel of a potential gamma ray burst event. The problem is that WR104 isn’t billions of light years away safely doing its thing in another galaxy. WR104 is only 8000 light years away, well within our own galaxy, and it could go pop at pretty much any time.
Perhaps it already has.
Maybe it went pop 7997 years ago and a high-energy gamma ray bullet traveling in excess of 99.995% the speed of light is well on its way to an encounter with Earth where it will dissolve our atmosphere and boil away our oceans in seconds -- just in time for the end of the Mayan calendar and the swearing in of Sarah Palin.
It’s like a game of Russian roulette on a cosmic scale. The earth is moving around the sun and the sun is orbiting around in the unfashionable end of the western spiral arm of the Milky Way galaxy. WR104 is closer in towards the galactic center than we are, orbiting at a different speed, and the dance that it does with its companion star twirls the pair and their potential gamma ray rifle barrel around like some kind of drunken marksman. The observations all point to WR104 going out with a bang instead of a whimper. All that remains to be seen is in what direction the barrel will be pointing on the day the trigger is pulled.
Scientists also suspect that this kind of ultimate laser tag game might have influenced life on our planet in the distant past. Much has been said about asteroid and comet impacts and the nuclear winter-type aftereffects that could result. At least one of the ‘Big Five’ mass extinctions, the Cretaceous–Tertiary extinction event 65 million years ago which ended the reign of the dinosaurs, is thought to be the result of such an impact. However, evidence suggests that the Ordovician–Silurian extinction event, 444 million years ago, may have been the result of a gamma ray burst originating within our galaxy.
I suppose the ultra paranoid amongst us could invest in some of that SPF 2,000,000 sun block and some lead undies and try to ride it out. Good luck with that.
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