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Formation And Evolution of The Solar System | Article 2

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Formation and evolution of the solar system.

The formation and evolution of the solar system begin 4.5 billion year ago with the gravitational collapse of a small part of a giant molecular cloud.most of the collapsing mass collected in the centre, froming the sun, while the rest flattened into protoplanetary disk out of which the planets moons, asteroid, and other small solar system bodies formed.

Formation and evolution
Formation and evolution

This model, known as the nebular hypothesis was first developed in the 18th century by Emanuel swedenborg, Immanuel Kant and Pierre Simon Laplace . Its subsequent development has interwoven a variety of scientific disciplines including astronomy, physics, geology, and planetary science. Since the dawn of the space age in the 1950 and the discovery of extrasolar planets in the 1990, the model has been both challenged and refined to account for new observation.

The solar system has evolved considerable since its initial formation.many moons have formed from searching discs of gas and dust around their parents planets, while other moons are thought to have formed independently and letter been captured by the planets.still others, such as Earth's moon, may be the result of joint collision.collisions between bodies have occurred continually up to the present day Central to the evolution of the solar system. The position of the planets might have shifted due to gravitational interaction. This planetary migration is now thought to have been responsible for much of the solar system's early evolution.

In roughly five billion years, the sun will cool and expand outward too many times its current diameter, before casting off its outer layer as a planetary nebula and leaving behind a stellar remnant known as White dwarf. In the far distant future, the gravity of passing stars will gradually reduce the sun's retinue of planets. Some planets will be destroyed, other eject into interstellar space.ultimately, over the cause of 10 of millions of years, it is likely that the sun will be left with none of the the original bodies in orbit around it.

  Formation

The nabular hypothesis says that the solar system formed from the gravitational collapse of a fragment of a giant molecular cloud. The cloud was about 20 parsec (65 light years) across, while the fragments roughly one parsec across.the further collapse of the fragments lead to the formation of dense cores 0.01-0.1pc (2,000-20,000 Au) in size. One of these collapsing fragments formed what became the solar system.the composition of this region with the mass just over that of the sun was about the same as that of the sun today, with hydrogen, along with helium and trace amount of lithium pronounced by bigbang nucleosynthesis, forming about 98% of its mass. The remaining 2% of the mass consisted of heavier elements that were created by nucleosynthesis in earlier generation of star. Late in the life of these stars, they ejected heavier elements into the interstellar medium.

Planets Origin
Planets Origin
The oldest inclusion found in meteorites, thought to trace the first solid material to form in the pre solar nebula,are 456 8.2 million year old, which is one definition of the age of solar system. Studies of ancient meteorites reveal traces of stable daughter nuclei of short lived isotopes, such as iron 16, that only form in exploding, short-lived stars.this indicates that one or more supernova occured near the sun while it was forming. Are shockwave from a supernova may have triggered the formation of the sun by creating relativity dense region within the cloud, causing the region to collapse. because only massive, short-lived stars produced supernova, the sun must have formed in a large star forming region that produce massive stars, possibly similar to the Orion nebula. Studies of the structure of the kuiper belt and off anomalous material within it suggest that the sun formed within a cluster of between 1000 and 10000 of stars with the diameter of between 6.5 and 19.5 light years and a collective mass of 3, 000. This cluster began to break apart between 135 million and 5:35 million year after formation. Several simulations of our young son interacting with close passing stars over the first hundred million years of its life produce anomalous orbit observed in the outer solar system, such as detached object.

Because of the conversation of angular momentum, then nebula spun faster as it collapsed. As the material within the nebula condensed, the atoms within it begin to collide with increasing frequency, converting their kinetic energy into heat.the centre, where most of the mass collected, became increasingly hotel than the surrounding disc. Over about 100,000 years, the competing forces of gravity, gas pressure, magnetic field, and rotation curved the contracting nebula to flatten into a spinning protoplanetary disc with a a diameter of about 200 AU and form a hot, dense protostar at the centre.

At this point in its evolution, the sun is thought to have Been a T Tauri star. Studies of T Tauri star show that they are often accompanied bi discs of pre-planetary matter with masses of 0.001-0.1 M. These discs extend to several hundred AU the Hubble space telescope has observed protoplanetary discs of up to 1000 AU in diameter and star forming regions such as the Orion nebula.and are rather cool Kumar reaching a surface temperature of only about thousand kelvins at their hottest. Within 50 million years, the temperature and pressure at the core of the sun became so great that its hydrogen begin to fuse, creating and internal source of energy that countered gravitational contraction until hydrostatic equilibrium was achieved. This marked the sun's entry into the prime face of its life, known as the main sequence. Main sequence star derived energy from the fusion of hydrogen into helium in their cores. The sun remains a main sequence start today.

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