The Sun is the star at the center of the Solar System and is by far the most important source of energy for life on Earth. It is a nearly perfect spherical ball of hot plasma.

The Sun is roughly middle aged and has not changed dramatically for for billions of years.The enormous effect of the Sun on the Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. Earth’s movement around the Sun is the basis of the solar calendar, which is the predominant calendar in use today.