Introduction History Glossary Page 2 of 2 Sunspots -Modern Research HOME Back  More About the Sun To better understand the process that creates sunspots we first need to learn more about the sun. The sun is by far the largest object in the solar system, containing more than 99.8% of the total mass of the solar system (Jupiter contains most of the rest). The sun is made of about 75% hydrogen and 25% helium by mass, with tiny trace amounts of metals and other compounds. Over time, the nuclear fusion reactions that fuel the sun are converting hydrogen into helium in its core, changing the ratio of the two elements. The energy produced by nuclear fusion in the core of the sun is carried outward by convective motions in the outer 20-30% of the sun, called the convection zone. Convection is the process by which hot gas from the center of the sun rises to the surface, and cooler gas, which comes to the surface and radiates its heat away, sinks back towards the center. The scale of the sun is hard to fathom. The sun is so large and so dense that it takes about 50,000,000 years for energy produced at its core to make its way to the sun's surface! The sun has been radiating light and heat for the past four or five billion years. The sunspots to which this site is devoted appear as tiny spots on the sun--but an average-sized sunspot is as large as the earth.