|GENERAL COMETS KNOWLEDGE|
Since humanity exists, comets ( for their variable look in time) are well-known and have always been fascinating man. They appear in the sky like celestial bodies with shape larger in the course of months and then their shape begins to become smaller and disappears in the course of few months. They come from regions in frontiers of solar system and occasionally some of these bodies disturbed by some near stars or by gravitational force of planets or by reciprocal impacts, hurry towards sun and become warmed by it.
click to enlarge the pictures
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
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
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
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
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.
The comets can deviate from their original
orbit cause the gravitational attraction of solar system bodies; some
comets (not periodical) can pass over closed orbits becoming periodical
and vice versa or they can collide against other bodies. For example:
from an original long period orbit (more than 500 years), to a passage
near Jupiter, the Halley comet passage was changed in a 76 years period.
Copyright © 2006 FOAM13