The late planetary bombardment
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Updated June 01, 2013
The mystery of the orbits of giant planets and planetary bombardment late is explained in three articles published in the journal Nature on May 26, 2005, the laboratory Cassiopeia (CNRS), an international collaboration of scientists: Rodney Gomes (Rio de Janeiro, Brazil), Hal Levison (Boulder, Colorado), Alessandro Morbidelli (Nice, France) and Kleomenis Gypsies (Thessaloniki, Greece).
The dark spots on the moon are huge impact basins that formed about 600 to 700 million years after the formation of the Earth and Moon.
The list and characteristics of craters on the Moon and Earth are one of the strongest evidence that attest to the late heavy bombardment. The number of planetesimals that have reached the Moon, according to the Nice model is consistent with the list and timing of impact craters observed on the moon during the late great bombardment, called the late heavy bombardment Late Heavy Bombardment or (LHB) in English. In these publications, the authors show that after the dissipation of gas and dust in the primordial solar disc, the four gas giants (Jupiter, Saturn, Uranus and Neptune) were on near-circular orbits at distances d about 5.5 to 17 astronomical units, much closer and more compact than today. In addition a dense disk (about 35 Earth masses), small planetesimals of rock and ice, extending from 17 to about 35 AU.
These planetesimals were slowly ejected in all directions, by the gravitational perturbations of the four planets. "As Isaac Newton taught us, every action causes an equal and opposite reaction...
If a planet ejects a planetesimal outside the Solar System, in compensation, the planet moves slightly towards the Sun. If the opposite the world sends the planetesimal inward, then it will move slightly away from the Sun." says the article in Nature, Kleomenis Gypsies.
The simulations show that Jupiter had to move towards the Sun while the other giant planets are far away.
Normally these trips should have been very slow, but depending on the model, after 700 million years, an abrupt change appeared.
Saturn is then exactly twice the distance of Jupiter. "This has made foolish the trajectories of Uranus and Neptune," says Rodney Gomes. "Their orbits became eccentric and they also began to violently disrupt them."
This model explains that this trend Nice orbits of Uranus and Neptune is the cause of the LHB.
Some of these planetesimals sent into the inner solar system, have produced violent impacts on terrestrial planets. Harold Levison, "we have made several dozen simulations of this process, and statistically the planets ended up on orbits very similar to those we observe, with separations, eccentricities and inclinations correct. So, in addition to the LHB We can also explain the orbits of giant planets."
Nice model is a scenario describing correctly the formation and evolution of the solar system. He suggested that the giant planets have migrated from a compact initial configuration to their current positions, long after the dissipation of the protoplanetary disk of gas.
This planetary migration explains the events as the late heavy bombardment of the inner solar system, the formation of the Oort cloud, the existence of populations of small solar system bodies including the Kuiper Belt, the Trojan asteroids of Jupiter and Neptune and the number of objects in resonance Transneptunian dominated by Neptune.
It is widely accepted as the most realistic model known to explain the evolution of the solar system, but it can not fully explain the formation of the Kuiper Belt.
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Image: The four Galilean moons of Jupiter.
From top to bottom: Io, Europa, Ganymede and Callisto. Jupiter has more than 60 known natural satellites whose names are drawn from Greek mythology.
Birth of the Solar System
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The event happens there are 4.5 billion years in the vicinity of a spiral arm of the Galaxy.
In a nebula of gas turning opaque, small clusters are formed. Among them, our future Sun escapes while his companions scatter in the Milky Way.
Central to this future system still gas, a star is formed, aided by the force of gravity, it contracts and will capture 99.86% of the total mass of the cloud.
During this period the juvenile core temperature increases. This cloud will contract again until reaching temperatures of several million degrees kelvin.
This heating of the heart will trigger the initiation of thermonuclear reactor.
In this phase the protons combine releasing energy under the influence of the nuclear force. It is the fusion of hydrogen into helium, which stops the contraction of the star and that stabilizes the volume.
In the solar system, the Sun has captured 99.86% of the total mass of dust and gas of the original nebula. Jupiter, the largest planet in the system, has captured 71% of the remainder.
The other planets are shared, the residue of the gravitational evolution.
Our Sun was born! remember that our Sun has captured 99.8% of the total mass of the system.
The rest of the hot gaseous nebula of departure, the composition is identical to that of the Sun, continues to lose heat. There comes a point where it reaches the temperature at which certain chemical compounds are more stable in the gaseous state.
These compounds are then condensed, not liquid but solid as the pressure is very low. The nebula is responsible therefore solid grains, dust, known as condensate. These are grains that, by accumulating as a result of gravitation, will give rise to solid objects larger and larger, first, to meteorites, and later, to the planets.
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Image: The Sun has captured 99.86% of the total mass of dust and gas of the original nebula. Jupiter, the largest planet in the system, has captured 71% of the remainder.
The other planets have shared the residue of the gravitational evolution.
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Image: The Solar System belongs to a galaxy called the Milky Way, among the billion galaxies make up the observable universe.
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