2.1 The Sun
The Sun is the dominating force of our solar system. It comprises 99 percent of the mass of the solar system and would require 109 Earth’s line up side-by-side to span its diameter. But the Sun is an average star in the universe and about 4.6 billion years old. If the Sun was more like a blue giant, meaning 10 times more massive, it would have died off long ago in a supernova; and if the Sun was smaller, it would not produce enough light and energy for life to exist.
Hydrogen accounts for 92.1 percent of all the atoms in the Sun followed by helium at 7.8 percent. The Sun is fueled by thermonuclear reactions at its core, in a process where hydrogen is fused to make heavier helium elements, which results in an enormous release of energy. The energy created by the sun is in the form of electromagnetic energy, which travels at the speed of light (299,792,458 meters per second) in a spectrum of varying wavelengths. Forty-three percent of the energy is in the visible spectrum, 49 percent as long wave radiation (also known as heat), and 7 percent as shortwave radiation such as X-rays, gamma rays and UV radiation. Ultimately, our star will begin to use up its energy and begin to expand into what astronomers called a red giant. That means it will grow and overtake Mercury, Venus, and possibly Earth and Mars. Over a few million years, it will shed its outer shell of gas into space, while the inner core compresses to become a white dwarf. Over time, the core will cool into a cold rock and then game over. |
Every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand. It really is the most poetic thing I know about physics: You are all stardust. You couldn’t be here if stars hadn’t exploded, because the elements - the carbon, nitrogen, oxygen, iron, all the things that matter for evolution and for life - weren’t created at the beginning of time. They were created in the nuclear furnaces of stars, and the only way for them to get into your body is if those stars were kind enough to explode." - A Universe From Nothing by Lawrence Krauss, AAI 2009
"Without the nuclear furnaces described to forge carbon, oxygen, and nitrogen, and without supernova explosions to seed hospitable places like earth, life could never form. As Sagan affectionately put it, “We are all star stuff.” Unfortunately, one sad truth of astrohistory is that Sagan’s “star stuff” didn’t grace every part of our planet equally. Despite supernovae exploding elements in all directions, and despite the best efforts of the churning, molten earth, some lands ended up with higher concentrations of rare minerals. Sometimes this inspires scientific genius. Too often it inspires greed and rapaciousness – especially when those obscure elements find use in commerce, war, or worst of all, both at once." - The Disappearing Spoon by Sam Kean
"Without the nuclear furnaces described to forge carbon, oxygen, and nitrogen, and without supernova explosions to seed hospitable places like earth, life could never form. As Sagan affectionately put it, “We are all star stuff.” Unfortunately, one sad truth of astrohistory is that Sagan’s “star stuff” didn’t grace every part of our planet equally. Despite supernovae exploding elements in all directions, and despite the best efforts of the churning, molten earth, some lands ended up with higher concentrations of rare minerals. Sometimes this inspires scientific genius. Too often it inspires greed and rapaciousness – especially when those obscure elements find use in commerce, war, or worst of all, both at once." - The Disappearing Spoon by Sam Kean