Saturday, July 25, 2009

2012 Pt. 2 - Death from Supernova

Here is the second part of what will probably be a several post expose on the 2012 "theory". I will focus on one or two events and go into some depth in each of them. Hopefully some interesting knowledge will be picked up instead of just debunking silly claims. Try googling 2012. You will find information about the movie that is coming out shortly as well as some remarkably irrational and intellectually lazy websites such as Survive 2012 among the thousands of hits that get returned. Herein lies a problem. If you accept ideas you read from a search engine query without skepticism it is easy to get drawn into a clusterfuck of poorly researched websites that belong in the fiction section of the internet.

On the front page of the aforementioned website it states "There is zero scientific evidence that anything will happen in 2012...", OK good start. Then the devolve into hypothesizing about random armageddon events that lack any causal relationship whatsoever with the Mayan calendar date of I will go over the space based events in this post and show that there is no evidence that any of them pose a threat on December 21st, 2012.

I will try to make this informative not just relating to 2012 but also in ways that the universe just may kill us in the future. The Cosmos can be a rather nasty place. Stellar events, radiation, explosions that make Hiroshima look like a firecracker, comets and asteroids hurdling by at many kilometers per second among many others have the potential to wipe out life as we know it on the planet earth. This will be very brief and I would recommend checking out Phil Plait's book Death from the Skies if you want more information on the topic. I haven't read it yet but I hear it is excellent.

The one I hear often is "Galactic Alignment". They postulate that the Earth, the Sun, and the Centre of the Milky Way will all be aligned on this winter solstice. The theories are rather convoluted and i encourage you to read more about it if you are curious but the end result is that nothing will happen. The Milky Way is around 7000 light years thick. The orbit of our solar system does slowly shift "up and down" as we happily orbit the center. This process takes millions of years. It is all a continuous process there is no dates where we can say that we are exactly in the middle because it is all rather fuzzy. Most of the other arguments that are made are taken from astrology. As soon as you see that you may as well stop reading. The most compelling, cogent argument needs to be tossed out if the premise in which it was based on is blatantly false such as astrology. If you want to read your horoscope for entertainment fine, not my business, but predicting the "End of Days" on it is just ridiculous.

The next one I will look at is the supernova. These are real and have the potential to kill us if we were within a specific radius. Luckily for us we know how supernovae happen and we are far enough away from potential candidate stars to be safe. These events happen at the end of a star's life. There are two main types of supernovae, they are designated type 1A and type 2. Type 2 supernovae occur when a massive star, several times the mass of our sun to around a hundred times the mass, to run out of fuel and explode.

Stars are a delicate balance of gravity and radiation pressure which I will get to in a moment. If you have ever dove into a pool or river deeper than 8 feet you will notice that as you descend you begin to notice the pressure on your ear drums. Now imagine a star it is REALLY big. It has tremendous gravity and therefore a great deal of pressure and 'pull' towards the centre. This pressure causes the star to heat up, increasing the speed that the atoms are banging into one and other until eventually they hit each other hard enough that they stick together. It is called nuclear fusion, which generates more energy than it consumes. You can picture it as climbing a roller-coaster where the drop at the end is longer than the hill approaching it. You need energy to climb the hill but once you get to the top you will exit with more speed than you started with. This energy is given off in the form of light. This light actually exerts a force, just like pushing against a wall in your home. Gravity however hasn't disappeared. Gravity wants the star to collapse into a single point since it is always attractive. Therefore this radiation pressure and gravity are locked in a delicate balance for the duration of the star's life.

The fun begins when it runs out of fuel, like a gambler sitting at a blackjack table who eventually runs out of chips (or my friends who bet stupidly large amounts of money on single hands of war). Gravity begins to win out. The radiation pressure simply isn't enough and it begins to collapse. During this collapse the gravitational potential energy heats of the material in the star and causes it to explode in a spectacular fashion. This explosions created all of the elements heavier than iron that we see today on the planet Earth. If a planet is within approximately 100 light years the energy released can be enough to do serious harm to a planet such as earth. Fortunately there are no nearby stars that are in danger of going supernova in the near future. The most likely candidate is Eta Carinae. It is a massive star approximately 9000 light years away. It could explode tomorrow or in 100,000 years. Astronomers do not know. Luckily we will just be treated to a spectacular light show in the sky, not armageddon.

The second type of supernova is called type 1A. This can occur in binary systems with stars similar to the mass of our sun. Smaller stars don't have this violent end. They slow enlarge as they age. Our sun will have a radius extending out past the orbit of Venus and possibly past Earth. Regardless we will be nicely toasted. It then sheds off its outer atmosphere and becomes a planetary nebula leaving behind a corpse, a white dwarf star. It no longer produces energy and will be approximately the size of the Earth slowly radiating away its heat and eventually cooling into a dead cinder. The density of this star will be mind boggling, approximately 1 metric tonne per cubic centimeter. That is similar to a freight train cargo container in a teaspoon. It is made out of electron-degenerate matter, I will leave it up to you to read up on that if you are interested.

If the white dwarf has a partner, which many do, matter can begin falling onto the corpse of the star. It happily builds up in an accretion disk around the star from matter being sucked in from its companion. It will continue to do this until it reaches a limit where gravity again becomes the enemy. At 1.38 stellar masses the pull of gravity is able to overcome the degeneracy pressure and cause a supernova. The star collapses and rebounds expelling tremendous amounts of energy and disappears in a cloud of energy and heavy elements.

So there you have it, galactic alignment is a hoax, and supernovae while real and amazingly cool are not close enough to hurt us. We can see the stars in our immediate neighbourhood and we don't have white dwarf binary systems accumulating matter or supergiants ready to collapse. Next time I'll look at 'rouge' planets, asteroids and gamma ray bursts.


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