The Oort cloud is a hypothetical set of small astronomical bodies, especially asteroids and comets, located beyond Pluto at the end of the Solar System.
In 1950 the Dutch astronomer Jan Oort, based on careful orbital studies and statistical analysis of the trajectories of comets, formulated a hypothesis, today commonly accepted, according to which, the nuclei of long-period comets come from a spherical cloud that surrounds the solar system beyond the orbit of Pluto, from about 30,000 astronomical units to about 3 light years.
These objects would have been formed in the first phases of accretion of the Solar System in the vicinity of the Sun, but would have been expelled to their confines by the effect of the forces of gravity. Those who did not totally escape these would have formed the Oort cloud.
Some of the objects in the Oort Cloud, because of the iteration with a nearby star, would be driven from time to time in the direction of the Sun, to which they would travel on a journey of hundreds of thousands of years until they began to alter its orbit by the effect of gravity of the great planets Jupiter and Saturn.
In this way, some bodies of the Oort Cloud become long-term comets, although others after passing through the nearby Solar System can be lost forever in outer space.
It is estimated, without data to support these hypotheses, that there are more than a billion small-diameter objects in the Oort Cloud, whose total mass can be equivalent to that of the planet Jupiter.
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