ABOUT THE SUN: The sun is a star, and like most stars, it's composed of hot gases: almost 75 percent hydrogen and 25 percent helium, with less than 1 percent being made up of oxygen and other elements. The source of the sun's energy is nuclear fusion. The nuclei of hydrogen atoms -- the simplest atoms, with one proton and one electron -- heat to such high temperatures (15,000,000 degrees Celsius) that they fuse together into helium nuclei ý with two protons and two electrons. In the process, they lose a small amount of mass, which is transformed into energy. Although the sun loses half a million tons every second, it will continue to shine for about five billion years. Once all the hydrogen in the sun's core is converted into helium, the core will contract and become even hotter, while the outer part will expand and become cooler -- it will become a red giant star. Eventually all sources of energy production will be consumed and the sun will collapse into a very small, hot object called a white dwarf.
CORONAL MASS EJECTION OR SOLAR FLARE? People sometimes confuse Coronal Mass Ejections (CMEs) with solar flares, but they are different phenomena. Solar flares are explosions on the sun that occur when energy build up around sunspots, becoming so hot -- millions of degrees Fahrenheit -- that they produce a burst of electromagnetic radiation across the entire electromagnetic spectrum, from radio waves to x-rays and gamma rays. CMEs were once thought to be the result of solar flares, but while they sometimes accompany solar flares, there is no direct relation between the two. They occur when a large bubble of plasma escapes through a star's corona and travels through space to the earth at high speeds over the course of several hours. If a CME collides with the earth, it can produce a geomagnetic storm, which can cause electrical power outages and damage communications satellites and electronic equipment. Solar flares, on the other hand, affect radio communications.
The American Physical Society contributed to the information contained in the TV portion of this report.