<P> The Solar System began forming about 4.6 billion years ago, or about 9 billion years after the Big Bang . A fragment of a molecular cloud made mostly of hydrogen and traces of other elements began to collapse, forming a large sphere in the center which would become the Sun, as well as a surrounding disk . The surrounding accretion disk would coalesce into a multitude of smaller objects that would become planets, asteroids, and comets . The Sun is a late - generation star, and the Solar System incorporates matter created by previous generations of stars . </P> <P> The Big Bang is estimated to have occurred about 13.799 ± 0.021 billion years before present . Since the expansion of the universe appears to be accelerating, its large - scale structure is likely to be the largest structure that will ever form in the universe . The present accelerated expansion prevents any more inflationary structures entering the horizon and prevents new gravitationally bound structures from forming . </P> <P> The Sun being a main sequence star, its future evolution can be predicted with some certainty . Over a timescale of a billion years or more, the Earth and Solar System are unstable . Earth's existing biosphere is expected to vanish in about a billion years, as the Sun's heat production gradually increases to the point that liquid water and life are unlikely; the Earth's magnetic fields, axial tilt and atmosphere are subject to long - term change; and the Solar System itself is chaotic over million - and billion - year timescales . </P> <P> Eventually in around 5.4 billion years from now, the core of the Sun will become hot enough to trigger helium fusion in its surrounding shell . This will cause the outer layers of the star to expand greatly, and the star will enter a phase of its life in which it is called a red giant . Within 7.5 billion years, the Sun will have expanded to a radius of 1.2 AU--256 times its current size, and studies announced in 2008 show that due to tidal interaction between Sun and Earth, Earth would actually fall back into a lower orbit, and get engulfed and incorporated inside the Sun before the Sun reaches its largest size, despite the Sun losing about 38% of its mass . </P>

How long after the big bang was it before protons and neutrons could form from quarks