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Sunday, February 3, 2013

Supernova


There are just over 100 elements in our Universe and many of them are found in each of us. I’ve been fascinated to learn over the years about how the elements were first created in the stars and then made available throughout our Galaxy so that they were accessible when we were evolving on planet Earth. I will attempt to tell that story in this post so that its marvels and violence are clearly revealed.

It’s a well-accepted scientific theory that in the beginning there was the ‘Big Bang’ when our Universe exploded into being as a condensed state of pure energy. That happened about 13.7 billion years ago and ever since it has been expanding. Evidence suggests that energy was converted into the most basic particles of matter through the relationship Einstein revealed in his famous equation: 
            E=mc2        where E stands for energy; m, for mass and 
                                c2, for the enormous speed of light multiplied by itself.                                 Many thousands of years later when things cooled further, atoms, most of them of the simplest element, Hydrogen, formed from the basic particles and the stage was set for the first suns to be born.

The distribution of matter was not entirely uniform in the early Universe and giant clouds of hydrogen tended to coelesce as the force of gravity drew them together. As the mass of the accumulation increased, the gravitational force became ever stronger until the nuclei of the Hydrogen atoms were smashing into each other so fast that they fused, forming the nucleus of the next heavier element Helium that, though made of two Hydrogen nuclei, weighs a little less. That mass was converted to heat energy and the temperature increased to around 15 million degrees Celsius.  To see a simulation of this process in which a star is born, click on the video.  

The colossal stars in the early universe were 1000 times larger than our sun and when all the Hydrogen was used up and converted to Helium, the core contracted. That caused an increase in temperature and the Helium nuclei began to fuse, again giving off energy, and forming the nuclei of the element Carbon. When all the Helium is used up, shrinkage again increases the temperature and carbon nuclei fuse. In the video showing this, I love how the two guys tell the story of how each element is formed until you come to the element Iron. When iron nuclei fuse, no mass is lost and so no energy is created and the star dies and begins to collapse inward. As the core falls in on itself, it bounces off sending a wave of material outward that hits the wave of the matter collapsing from the outer layers and then a stupendous explosion occurs called a supernova that flashes in the sky with the light equivalent to that given off by 4 billion smaller stars like ours and can be seen from Earth.  In that whole energetic process, the rest of the elements are formed and spewed with tremendous momentum throughout the galaxy as stardust. We are made of that stardust!  Rie

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