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From Kupier cloud comes the comets that usually are beyond Pluto’s orbit, they lie on the ecliptic’s plane and have elliptic orbits.

From the  depth of the solar system and beyond it, comets come from Oort cloud, the rest of interstellar cloud in which was born our solar system. This big cloud contains an area between 50.000 and pheraps 150.000 astronomical unites (an astronomical unite means 150.000.000  kilometres). If we convert this distance in light year we get to know that Oort cloud lies between 0,8 and 1,5 light years from the Sun, these comets come from all the directions and approach to the Sun with open orbits (they are parabolic or iperbolic).

For the Kupier cloud case, the comets will periodic , the Oort cloud after it transit near the Sun will disappear in the space and  will never return. These bodies that have small dimensions, when they arrive in Jupiter’s orbits, the heat of Sun spurs the evaporation of shallow ice. The steam so free drags small dusts that diffuses solar light making sparkling these things.

A “coma” forms  around the nucleus and it is usually the first sign of the cometary nature of this body in approaching. The “coma” develops itself in a tail on the opposide side of  the Sun direction, it’s caused by the pression of radiation and by the particles that form solar wind. Thanks to formation with low temperature and to distance from other bodies, the stuff of which is made the nucleus of comets gives us some important information about the initial chemical composition of solar system. From this argument there is the interest for the missions that are able to lodge tools directly on nucleus or to bring again towards earth some cometary specimens.

The big quantity of water in  the nucleus and the organic matter found in dusts of coma and of tail, can affect the oceans origin and the earth atmosphere and the beginning of life.

The interest for the glamorous comets,  has deep scientific motivation that studies the beginning of our planetary system.

A comet  (during every transit  near sun) loses a part of his composition and after every transit towards perihelion runs out and  leaves in the space detritus and dusts.

After a period of transits the comet  disintegrates itself because the  reciprocal attraction of its components cannot join them. Earth during his motion goes across these fragments. They enter in its atmosphere producing the “meteoritic rains”, that go on regurlary in the same time during a year.

The Perseidi swarm is very famous, that earth goes across on 9th  and on 13th  august, this phenomenon gives rise to fallen stars at St Lorence night; instead earth crosses Orionidi swarm in October.