03 May 2012
SECRETS OF THE SUN
Life on Earth would not be possible without the constant flood of energy from our closest star, the Sun. Yet that same energy would fry us to a cinder if (a) we were not in a safe orbit 93 million miles away, and (b) Earth were not protected by a magnetic field which deflects nearly all the Sun's harmful radiation from the planet's surface. Our sun is a nuclear fusion furnace, with a surface temperature of around 10,000 degrees Farenheit (dF), and a core temperature of 27,000,000 dF. It is so massive that it accounts for 99.86% of the total mass of the solar system. If you were to line up 109 Earths in a row, you would have the diameter of the sun. Its surface area is 12,000 times that of Earth, and its volume is 1,300,000 times the volume of Earth. All that mass produces a surface gravity 28 times as strong as Earth's.
Until recently we had little understanding of the powerful, complex forces with operate within the Sun. We understood that energy is transferred by convection, conduction, and radiation, but we did not have a grasp on how that might relate to the Sun's own magnetic field, or to the planet-sized sunspots (see image above - each 'cell' surrounding the darker, hotter sunspot could swallow the state of Alaska) and solar storms which go through an eleven-year cycle of greater or lesser intensity, or to the solar prominences which geyser in graceful arcs hundreds of thousands of miles high.
Thanks to orbiting solar observatories, robotic spacecraft, and powerful computer modeling, our grasp of the Sun's inner workings is starting to clarify. The PBS series NOVA recently aired a spectacular program entitled Secrets of the Sun. The visuals are stunning, and the sheer scale of the Sun's interacting layers, currents of plasma, and magnetic field is hypnotic. The knowledge comes just in time, too. In the past, the sun has experienced superstorms which penetrated Earth's magnetic field defense ~ but we have not experienced one since the advent of satellite communication, the Internet, global air travel, and a complex power grid. Understanding how to accurately predict solar superstorms is essential if we are to survive its effects.