An Assessment the Sun
...ly, with no one to replenish the woodpile, the Sun will grow cold and dark -- plunging our region of the galaxy back into darkness (Distinguishing facts from myths, 2003). The Sun's energy output (3.86e33 ergs/second or 386 billion billion megawatts) is produced by nuclear fusion reactions. Previous measurements have demonstrated that the total radiant energy from the Sun was not a constant. However, the solar variability was so slight (0.1 percent) that continuous monitoring by state-of-the-art instrumentation is necessary. Researchers theorize that as much as 25 percent of the anticipated global warming of Earth may be solar in origin. Small changes in total solar irradiance by the Sun over a century or more may cause significant climate changes on Earth (ACRIMSAT 2000). Fusion in the core of the Sun releases energy and that energy works its way gradually outward through the Sun's inner layers until it reaches the photosphere, the visible surface of the Sun and the site of the sunspots discovered by Galileo. The photosphere is also the site of boiling convective motions. Above the photosphere is the chromospheres that is the transition from photosphere to the Sun's outermost region, the corona. Radiation from the Sun's nuclear core works outward through the convection zone - a spherical shell in which the solar atmosphere turns over. The photosphere is the Sun's visible surface. The solar surface has a mottled appearance containing occasional dark sunspots from which rope-like magnetic fields rise and descent (Cutaway of Sun's Structure 2002). The Sun is kept stable by its internal pressure. Just as pressure increases as you dive deeper and deeper into the Earth's oceans, so pressure increases as you dive deeper and deeper into the Sun. By the time you reach the Sun's center, the pressure has reached a value equal to 340 billion times the air pressure at sea level here on Earth. It's a general rule that gas flows from regions of high pressure to regions of low pressure. Within the Sun, therefore, pressure creates an outward force, from the high-pressure core to the low-pressure surface. This is in contrast to gravity, which creates an inward force. When the force due to pressure exactly balances the force due to gravity, a system is in hydrostatic equilibrium. The Sun's hydrostatic equilibrium is stable and self-regulating; if you tossed a little extra matter onto the Sun, the inward force of gravity would increase. However, the resulting compression would increase the pressure inside the Sun, resulting in an increase in the pressure force just sufficient to balance the increased gravitational force (Ryden, 2003). Astronomers listen to the Sun to learn more about it's inside. The s...