In the past people believed the Sun to be a burning celestial object. Today's opinion is that the Sun was formed about 4.6 billion years ago. In 1998 accredited scientists set the age of the Sun at 4.5 billion years (plus/minus 0.1 billion years). This information was gained through theoretical calculations of the ages of stars.
The theory states that a huge cloud of dust particles and hydrogen drifted through space as a dark_nebula. The pressure waves of a massive explosion caused it to begin to move and the matter began to contract under its own gravity.
Over the next 50 million years this process continued, until it had the size of the Sun today. Temperature and pressure rose on the inside because of the contraction of the gases. When a certain temperature was reached, the contraction ended and hydrogen fusion began. The Sun began to shine brightly and has remained in this state to this day.
According to calculations, the Sun will be able to continue its activity for another 4.5 billion years. Then the hydrogen reserves in its interior will be exhausted and it will collapse. This will cause a new surge of energy and the internal temperature will rise higher than ever before. The outer gas layers will expand and the Sun will become a red giant. It will be 500 times brighter and 100 times bigger than the Sun and will fill the entire sky as seen from the Earth. The Earth itself will not fall into the grasp of the mass of the red giant. It will already have been hurled outwards into space.
After a renewed phase of cooling and contraction the Sun will collapse and contract to become a white dwarf. During the following millions of years it will cool down continuously.
