Solar astronomy is the scientific study of the celestial star we refer to as the sun and the phenomena that surround it. The main concerns of solar astronomy are the physics, chemistry, meteorology, motion and evolution of the sun as well as its place in the universe.
Historically, astronomy is one of the Earth's oldest sciences. In early civilizations astronomers would perform methodical observations of the night sky, but it was not until the invention of the telescope that astronomy was able to grow and develop into the science that we know today.
Because the sun is the physically closest star to the Earth, which is about eight light-minutes away, it is the most frequently studied star.
Our sun is categorized as a typical yellow main-sequence dwarf star of the stellar classification G2 V and is said to be about 4.6 billion years old. The sun makes up about 99% of the total mass of our solar system.
Through the study of solar astronomy scientists have also discovered that the sun goes through an 11-year cycle of periodic changes in activity which they call a sunspot cycle. A sunspot is a region on the sun that has intense magnetic activity which forms an area with lower than average surface temperature. During a sunspot cycle the number of sunspots on the surface of the sun fluctuates.
Solar astronomers have also discovered that the sun has slowly but steadily increased its luminosity by 40% since it first became a main-sequence star. There have also been changes in the sun's luminosity that have directly affected the Earth
The solar astronomer Edward W. Maunder discovered that during the period between 1645 to 1715 sunspot were exceedingly rare. In that time period astronomers observed only about 50 to 60 sunspots where there are usually around 40,000 to 50,000 sunspots. This phenomenon was named the Maunder Minimum and it was noted that is occurred in the middle of the "Little Ice Age", a time which much of the world was subjected to extremely harsh winters. Whether or not the sunspot activity and the cold winters were merely a coincidence is still an ongoing debate in the scientific community.
Although the sun does not have standard boundaries like a rocky planet such as Earth, it does have a well defined interior structure which is made up of extremely hot gases and surrounded by the photosphere. Because the photosphere is too cool and too thin to radiate a significant amount of light, the surface of the photosphere is the most easily visible part of the sun to the naked eye.
The layer above the photosphere is known as the solar atmosphere which consists of four parts the chromosphere, the transition region, the corona and the heliosphere. The heliosphere while considered the weakest part of the sun's atmosphere extends all the way out past the orbit of Pluto.