The Sun

The sun is the star that is at the center of the solar system. Both the earth and all other planets orbit around the sun. The sun itself provides the energy that we receive as sunlight. This energy helps to support all forms of life on earth including plants, which use the sun through the process of photosynthesis.

Throughout history our perception of the sun has changed. At one point it was simply seen as a large luminous disk in the sky that when looked at above the horizon it would give off light during the day and it would disappear at the end of the day. In some cultures around the world the sun was looked at as being a supernatural phenomenon or a superior deity. Many important structures around the world we built around the idea of the sun and its importance.

Over time people began to look at the sun from a scientific point of view. In the times of the Ancient Greeks, philosophers such as Anaxagoras believed that the sun was really a burning ball of fire. As a result of his teaching this to others he was sentenced to death because it was thought that he was telling lies. The theory that the sun was the center of the universe around which the earth and all other planets was proposed by another Ancient Greek philosopher, Aristarchus. Through the development of the telescope, Galileo was able to make some of the first observations of sunspots. Chinese astronomers also were observing sunspots at the time of Han dynasty.

NASA has had several missions completed in which people were sent to observe the sun. The first satellites were launched between 1959 and 1968. The probes were able to orbit the sun at a distance similar to that of the Earth. It was through these probes, NASA was able to make detailed measurements of the solar wind and the solar magnetic field. Pioneer 9 transmitted a great deal of information in 1987.

One of the most important solar missions was completed in December 1995. The Solar and Hemispheric Observatory mission was originally a two- year mission but lasted for ten years. Due to the useful information obtained from this mission a follow-up mission was created. Not only did NASA obtain information about the sun during this mission, but they were also able to obtain information about a large number of comets as they passed the sun.