Asteroids
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The different groups of asteroids (Atens,Amors,Apollos,Trojans,TNOs) are one one of
the best studied celestial bodies at the ADG in Vienna. Different research work has
been done to explain the stability properties of these objects and to investigate
their collision possibilities.
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The Asteroid Belts
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On distinguishes four different asteroidal belts in our solar system.
There are :
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- the NEAs the Near Earth Asteroids (1)
- the Mainbelt between Mars and Jupiter (2)
- the Trojanbelt in the 1:1 resonance with Jupiter (3)
- the Kuiperbelt outside the neptunian orbit (4)
In the diagram above, you can see the different gaps an groups in the asteroid distribution
of the main belt.Their reason are the resonances : If the orbital movement of an asteroid
and an major planet shows an integer relation (i.e. if Jupiter performs 1 revolution, a
trojan asteroids performs also 1 revolution -
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this is the 1:1 resonance), then this can result
in a stabilisation or perturbation of the asteroidal orbit. You can see the so called
Kirkwood gaps, i.e. at the 3:1 or the 5:2 resonance.
The picture on the right shows the Kuiperbelt, which surrounds our solarsystem.
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The "mysterious" event at Tugunska in Sibira whas the effect of a huge
meteor impact, which exploded before it hit the earth, the effects of the shockwave are
visible in the picture |
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A Tsunami - a giant flood wave - is an event, which is caused by an impact in the ozean.
But it can also be caused by earthquakes under the sea.
65 million years ago, a giant meteor hit the northern part of the mexican peninsula
Yucatan.
This has caused the dying of the dinosaurs. On satellite photos one can see the crater with
an diameter of 200 km !
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Collision with Atens ?
The NEAs, the Near Earth Asteroids kann be divided in 3 different groups :
- the ATENS, with an semimajor axis smaller than that of earth
- the APOLLOS, with an semimajor axis bigger than that of earth
- the AMORS, witch do not cross the earth orbits and stay inside the orbit of mars
In a work of R.Dvorak and E.Pilat-Lohinger, the Aten encounters with earth and venus had
been examined. For this calculations 4 different modells were used. A 9 body system (the
whole solar system), one with 8, one with 6 bodies and one just with sun, earth,mars and
jupiter.The result of some test caculation showed, that the 6 body system (Solarsystem
without mercury, uranus, neptune and pluto) gives the best results.
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On the 3 pcitures on the right you can see, that the encounters of the ATENS with earth
and venus correlates with jumps in inclination and semimajor axis. This special asteroid
(2062 ATEN) later develops to an APOLLO. The table below shows the different encounters
with earth .The Earth encounter with the asteroid 34955, which
happens 5000 years ago, could be observerd by the ancient cultures, because the object was
bright enough to be seen. The second table shows, that their is a bigger probability for the
ATENS to hit the venus, than the earth.
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