The Sun

The Sun By John Smardon

It is interesting how one would teach astronomy from an instructors’ point of view. One of the first things to be taught would have to be an understanding of magnitude and scale. From the very large to the very small, in our solar system as it is today, the Sun would be a logical place to begin. The sheer enormity of the Sun makes it the largest single mass in the galaxy, as well as the sole provider of energy for life itself. After learning about the sun and other stars, a better understanding of the entire universe is gained. Facts about the size and scale of the Sun are endless. The diameter of the sun is approximately one hundred and nine times that of Earth and has an equatorial circumference of 4,379,000 Km. Over one million Earths (1,299,000) would fit inside the spherical area the Sun occupies. It is estimated that the Sun weighs (mass) roughly 1.99 x 1030 kg! The mass also decreases over time as fusion reactions convert hydrogen atoms into helium. These fusion reactions convert mass into energy, which is released into space as visible light, ultraviolet light, gamma rays, X- rays, radio waves, infrared and microwaves, known as solar wind. Einstein’s theory of relativity (E=mc2), equates this mass/energy transformation. Despite the shrinking mass, the Sun still manages to contain more than 99.8% of the total mass of the entire solar system (Jupiter makes up the majority of the rest). It is so large that its gravity controls the orbits of all things in our solar system. The Sun is one of 100 billion stars in our galaxy but is considered to be in the top 10% by mass. There are giant stars in existence that have as much as 100 solar

masses (having a mass 100 times that of our Sun). There are also stars that have immense size that are referred to as red giants. The red giants are stars that have reached the final stages of their life and this explains their swollen state. One such star called Betelgeuse is 1000 times larger and 50000 times more luminous, despite being only 20 times more massive. The Sun is primarily made up of gas and has no solid surface, The predominant element in the Sun is hydrogen, and then helium: by mass, it is 70% hydrogen, 28% helium, 1.5% carbon, nitrogen and oxygen, and 0.5% all other elements. We expect stars of the Sun's size to be composed mainly of hydrogen and helium since these are the elements formed shortly after the Big Bang, whereas all other elements are made during a star's life or death. More interestingly, we know that the Sun is not big enough to make the 0.5% "other" elements for itself: this means that the Sun is not a first generation star but formed in a region where more massive, violent stars once lived. The core starts from the center and extends to 25 percent of the sun's radius. Here, gravity pulls all of the mass inward and creates an intense pressure. The pressure is high enough to force atoms of hydrogen to come together in nuclear fusion reactions. Two atoms of hydrogen are combined to create helium-4 and energy in several steps. The helium-4 atoms are less massive than the two hydrogen atoms that started the process, so the difference in mass was converted to energy as described by Einstein's theory of relativity (E=mc2). The energy is emitted in various forms of light (ultraviolet light, Xrays, visible light, infrared, microwaves and radio waves). The sun also emits energized particles (neutrinos, protons) that make up the solar wind. This energy strikes Earth, where it warms the planet, drives our weather and provides energy for life. We are not

harmed by most of the radiation or solar wind because the Earth's atmosphere protects us. Every second 700 million tons of hydrogen are converted into helium. In the process 5 million tons of pure energy is released; therefore, as time goes on the Sun is becoming lighter. The Sun appears to have been active for 4.6 billion years and has enough fuel to go on for another five billion years or so. At the end of its life, the Sun will start to fuse helium into heavier elements and begin to swell up; ultimately growing so large that it will swallow the Earth. After a billion years as a red giant, it will suddenly collapse into a white dwarf (the final end product of a star like our sun). It may take a trillion years to cool off completely. A typical white dwarf is half as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars which are the end product of very large stars. A neutron star is about 20 km in diameter and has the mass of about 1.4 times that of our Sun. This means that a neutron star is so dense that on Earth, one teaspoonful of its matter would weigh a billion tons! Because of its small size and high density, a neutron star possesses a surface gravitational field about 2 x 1011 times that of Earth. The Sun is not only the provider for life on Earth. Unless another catastrophic event destroys the Earth, The dying phases of the Sun most certainly will. The study of the Sun has indeed revealed some amazing things regarding all aspects of chemistry and physics. Who knows what other secrets are yet to be told. The origins of life or the origins of Earth may be contained within. As long as humans are bound by the vast distances that lay between even our closest neighbors, the Sun will be an object of great interest. The potential for the gathering of scientific information has been shining

down upon the Earth for 4.5 billion years and will continue to shine for an estimated 4.5 billion more.

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