The Sun

The Sun, the nearest star to Earth, provides the energy necessary for life.The Sun is the largest body in our solar system; in fact, it accounts for 99.8% of the mass of our entire solar system. It is a sphere of gas made up mostly of hydrogen and helium. Because these gases are almost completely ionized, they form a plasma. Hydrogen is transformed to helium in the center, which releases vast quantities of energy in the form of photons and thermal motions, known as gamma rays. The Sun, like the other gaseous planets has differential rotation. The surface rotates once every 25.4 days at the equator, but takes about 36 days to rotate at the poles. The core, however, rotates as a solid body.

The sun has a very large magnetic field with a magnetosphere that extends beyond Neptune and Pluto. The magnetic field helps to cause sunspots, which are cool regions on the surface (called the photosphere). Sunspots may be as large as 50,000 km in distance. Above the photosphere is a layer called the chromosphere, and above the chromosphere is the corona, which extends into space but can only be seen when there is an eclipse.