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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. [ 121 ] [ 122 ] Within 7.5 billion years, the Sun will have expanded to a radius of 1.2 AU (180 × 10 ^ 6 km; 110 × 10 ^ 6 mi)—256 times its current size.
Earth formed in this manner about 4.54 billion years ago (with an uncertainty of 1%) [25] [26] [4] and was largely completed within 10–20 million years. [27] In June 2023, scientists reported evidence that the planet Earth may have formed in just three million years, much faster than the 10−100 million years thought earlier.
Impurities in the A-cloud formed Mars and the Moon (later captured by Earth), impurities in the B-cloud collapsed to form the outer planets, the C-cloud condensed into Mercury, Venus, Earth, the asteroid belt, moons of Jupiter, and Saturn's rings, while Pluto, Triton, the outer satellites of Saturn, the moons of Uranus, the Kuiper Belt, and the ...
Diagram of the early Solar System's protoplanetary disk, out of which Earth and other Solar System bodies formed. The Solar System formed at least 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud. [b] This initial cloud was likely several light-years across and probably birthed several stars. [14]
HD 189733 b forms around parent star HD 189733: the first planet to reveal the climate, organic constituencies, even colour (blue) of its atmosphere; 13.345 billion years (455 Mya): Vega, the fifth-brightest star in Earth's galactic neighbourhood, forms. 13.6–13.5 billion years (300-200 Mya): Sirius, the brightest star in the Earth's sky, forms.
c. 4,450 Ma – 100 million years after the Moon formed, the first lunar crust, formed of lunar anorthosite, differentiates from lower magmas. The earliest Earth crust probably forms similarly out of similar material. On Earth the pluvial period starts, in which the Earth's crust cools enough to let oceans form.
According to evidence from radiometric dating and other sources, Earth formed about 4.54 billion years ago. [7] [8] [9] The current dominant theory of planet formation suggests that planets such as Earth form in about 50 to 100 million years but more recently proposed alternative processes and timescales have stimulated ongoing debate in the planetary science community. [10]
In 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years. [19] [20] He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface temperature gradient to decrease to its present value.