Editing Sun (section)

==Fate of the Sun==

[[Astrophysics|Astrophysicists]] say our Sun is a [[G-type main-sequence star]] in the middle of its [[stellar evolution|life]]. In about billion years, increased solar energy will boil away the [[Earth's atmosphere]] and oceans. In a few more billion years, they think the Sun will get bigger and become a [[red giant]] star. The Sun would be up to 250 times its current size, as big as {{convert|1.4|AU|km mi|abbr=in|lk=in}} and swallow up the Earth.

[[Earth]]'s fate is still unknown. In the long term, the Earth's future depends on the Sun, and the Sun is going to be fairly stable for the next 5 [[billion]] years.<ref>[http://faculty.wcas.northwestern.edu/~infocom/The%20Website/evolution.html The Sun's evolution]</ref><ref>Goldsmith D. & Owen T. 2001. ''The search for life in the universe''. University Science Books, p. 96. {{ISBN|978-1-891389-16-0}}</ref>  Calculations suggest that the Earth might move to a wider orbit. This is because about 30% of the Sun's mass will blow away in the [[solar wind]]. 

However, in the very long term the Earth will probably be destroyed as the Sun increases in size. Stars like the Sun become [[red giant]]s at a later stage.<ref>Schröder K.-P. & Smith R.C. 2008. Distant future of the Sun and Earth revisited. ''Monthly Notices of the Royal Astronomical Society'' '''386''' (1): 155–163. [http://mnras.oxfordjournals.org/content/386/1/155]</ref> The Sun will expand beyond the orbits of [[Mercury (planet)|Mercury]], [[Venus]], and probably Earth. In any event, the ocean and air would have vanished before the Sun gets to that stage.

After the Sun reaches a point where it can no longer get bigger, it will lose its layers and form a [[planetary nebula]]. Eventually, the Sun will shrink into a [[white dwarf]]. Then, over several hundred billion or even a trillion years, the Sun would fade into a [[black dwarf]].