Editing Sol (section)

==Life cycle==

The Sun's current main sequence age, determined using computer models of stellar evolution and nucleocosmochronology, is thought to be about 4.57 billion years. 

It is thought that about 4.59 billion years ago, the rapid collapse of a hydrogen molecular cloud led to the formation of a third generation T Tauri star Population I star, the Sun.  The nascent star assumed a nearly circular orbit about 26,000 light-years from the center of the Milky Way Galaxy. According to the University Of Hawaii's Astronomical Sciences Department, the Ca-Al-I's (= Ca-Al-rich inclusions) here formed in a proplyd (= protoplanetary disk). Protoplanetary disk  are never older than 25 Ma. If 4567 Ma is given for the age of the Earth, then 4567 + 25 = 4592. But 25 Ma is the "maximum age" of proplyds. If proplyds slowly decay from the influence of the Sun and from planetesimal formation, then most Ca-Al-I's must have been formed some time within the range of 0 Ma and 25 Ma after the formation of the proplyd. If the median of Ca-Al-I ages are about 10 Ma after the proplyd formation, then we get 4565 + 10 = 4575, but this figure is created by speculating twice. Since it is assumed that planetary formation occurs over a period of about 100,000 years, that is the date given here

The Sun is about halfway through its main-sequence stellar evolution, during which stellar nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than 4 million tonnes of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation; at this rate, the Sun will have so far converted around 100 Earth-masses of matter into energy. The Sun will spend a total of approximately 10 billion years as a main sequence star.

The Sun does not have enough mass to explode as a supernova. Instead, in about 5 billion years, it will enter a red giant phase, its outer layers expanding as the hydrogen fuel in the core is consumed and the core contracts and heats up. Helium fusion will begin when the core temperature reaches around 100 million kelvin and will produce carbon, entering the asymptotic giant branch phase. 

Earth's fate is unclear. As a red giant, the Sun will have a maximum radius beyond the Earth's current orbit,  of 1 AU, 250 times the present radius of the Sun. However, by the time it is an asymptotic giant branch star, the Sun will have lost roughly 30% of its present mass due to a stellar wind, so the orbits of the planets will move outward.  If it were only for this, Earth would probably be spared, but new research suggests that Earth will be swallowed by the Sun owing to tidal interactions. Even if Earth escapes incineration in the Sun, its water will be boiled away and most of its atmosphere would escape into space.  In fact, even during its life in the main sequence, the Sun is gradually becoming more luminous (about 10% every 1 billion years), and its surface temperature is slowly rising.  The increase in solar temperatures is such that in about a billion years, the surface of the Earth will become too hot for liquid water to exist, ending all terrestrial life. 

Following the red giant phase, intense thermal pulsations will cause the Sun to throw off its outer layers, forming a planetary nebula. The only object that will remain after the outer layers are ejected is the extremely hot stellar core, which will slowly cool and fade as a white dwarf over many billions of years. This stellar evolution scenario is typical of low- to medium-mass stars.