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By 10 million years, gas in the protoplanetary disc has been blown away, and outer planet formation is likely complete. [38] 10 million – 100 million years 4.5–4.6 bya: Terrestrial planets and the Moon form. Giant impacts occur. Water delivered to Earth. [2] Main sequence 50 million years 4.5 bya: Sun becomes a main-sequence star. [32] 200 ...
[31] [68] Searches as of 2011 have found that core accretion is likely the dominant formation mechanism. [68] Giant planet core formation is thought to proceed roughly along the lines of the terrestrial planet formation. [20] It starts with planetesimals that undergo runaway growth, followed by the slower oligarchic stage. [65]
French philosopher and mathematician René Descartes was the first to propose a model for the origin of the Solar System in his book The World, written from 1629 to 1633.. In his view, the universe was filled with vortices of swirling particles, and both the Sun and planets had condensed from a large vortex that had contracted, which he thought could explain the circular motion of the plane
A planet's year depends on its distance from its star; the farther a planet is from its star, the longer the distance it must travel and the slower its speed, since it is less affected by its star's gravity. No planet's orbit is perfectly circular, and hence the distance of each from the host star varies over the course of its year.
Thus, the Sun occupies 0.00001% (1 part in 10 7) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 −6) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune, is 30 AU ...
The history of planetary science may be said to have begun with the Ancient Greek philosopher Democritus, who is reported by Hippolytus as saying . The ordered worlds are boundless and differ in size, and that in some there is neither sun nor moon, but that in others, both are greater than with us, and yet with others more in number.
If formed in the gravity field of a planet as the planet is forming, a moon will orbit the planet in the same direction as the planet is rotating and is a regular moon. If an object is formed elsewhere and later captured into orbit by a planet's gravity, it can be captured into either a retrograde or prograde orbit depending on whether it first ...
Viktor Sergeevich Safronov (Russian: Ви́ктор Серге́евич Сафро́нов) (born Velikie Luki; 11 October 1917 in Russia – 18 September 1999 in Moscow, Russia) was a Soviet astronomer who put forward the low-mass-nebula model of planet formation, a consistent picture of how the planets formed from a disk of gas and dust around the Sun.