What is a solar nebula?
It is assumed that our solar system was formed about 4.6 billion years ago from a large cloud of gas and dust, measuring several light -years in average, known as the Nebula. This cloud consisted mainly of hydrogen gas with a smaller number of elements that now form the solar system. According to solar nebula theory, some of this cloud began to download gravity, probably due to the disruption of the nearby supernova or the passage of another star, and, as was the case, the initial slow cloud rotation began to increase, causing it to match the disk shape. As more material accumulates in the center of the disk, the density and temperature reach the point where the fusion of hydrogen atoms began, created helium and released a huge amount of energy, resulting in the birth of the sun. Planets, asteroids and comets made of residual material.
Over time, another collapse was stopped by the sun reaching hydrostatic balance. The solar wind from the young sun scattered a large part of the material in the solar mLhovina, reduced its density and the nebula began to cool. In addition to the three lightest elements - hydrogen, helium and lithium - the elements of which were composed of the solar nebula were either made up of nuclear fusion in the stars, now long gone, or in the case of elements heavier than iron, created by supernovae. Simple covalent molecules were also present, including water, methane and ammonia and ionic molecules such as metal oxides and silicates. Initially, as a result of high temperatures on the disk, these compounds would be gaseous, but as cooling, most elements and compounds condensed into small particles; Metals and ion compounds were first condensed due to their higher boiling and melting.
Near the center of the disk, metals, metal compounds and silicates prevailed, but further, where the temperatures were lower, large amounts of ice condensed from the nebula. In this outer area, gaseous hydrogen and helium were also abundant; These gases were largely dispersed by the sun wind closer to the sun. Tiny fixed particles withThey knocked down and stuck together to create more and more objects that began to attract more gravity material, which eventually led to the formation of planets. In the inner solar system, there was a lack of ice, hydrogen and helium to the formation of a relatively small planet mercury, Venus, Earth and Mars, composed mainly of a rock. Further out, aggregated LEDs and mineral particles that make up larger bodies that have been able to maintain light gases and helium through relatively strong gravitational fields, resulting in "gas giant" planets, Jupiter, Saturn, Uranus and Neptune.
The theory of solar nebula is a number of key features of our solar system. Fact that the planets - with the exception of Pluto, which are no longer considered a planet - all lies in more or less the same planes and the fact that everyone orbits the sun in the same direction, suggests that they have arisen from the disk surrounding the sun. The presence of relatively small rocky planets in the inner solar system and gas giant in the outer areaIt also fits well into this model.
Behind Neptune, the farthest planet, lies the buyer belt, a area of relatively small objects composed of a rock and ice. It is assumed that Pluto could have arisen here and that the comets are objects of the Kuiper belts that have been pushed into the orbit that brings them to the inner solar system. The Kuiper belt is also well explained by the theory of the solar nebula as resulting from the rest of the ice and the rocky material too distracted to form planets.
Further evidence supporting this theory comes from anywhere on the mammary path. Astronomers can study parts of our Galaxy, where stars, such as Orion Nebula, are currently formed, a large volume of gas located in the constellation of Orion. Most of the new stars in this nebula are surrounded by gas and dust discs, which are expected to eventually be formed planets.