“
Catch a star ! “ |
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THE MOON
SUMMARY
III. Physical characteristics of the Moon IV. Tides VI. Experiments 1 -Procedure 2 - Observations, acquisition and image processing 3 - Assumptions 5 - Conclusions VII. Personnal
conclusion VIII. References
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Three theories are proposed to explain the
origin of the Moon :
1 - The theory of Fission
: The rotation of the Earth was 10
times faster than today and under the effect of the tides of the Sun, parts of
the external layers would have been rejected and would have accumulated to form
the Moon.
2 - The theory of capture: the Moon would have
been formed by agglomeration of the matter of a protoplanetary disc in which
metals were missing.
3 - The theory of
collision: a giant asteroid (8 times
as large as the Moon) hit the Earth on its side. At the time of the
"crash" parts of the earth’s crust was projected into space, forming
the Moon, whereas the metal core of the asteroid agglomerated with that: of the
Earth by fusion.
from” Astronomie et
astrophysique”
The first historic observation :
The first man who really observed the Moon was Galileo
because he observed the Moon with a refractor of 30 mm aperture.
II- Discovery of the Moon
The discovery of the moon was
realised by observations from Earth and with space probes.
|
year |
country |
results |
Luna-1 |
1959 |
U.S.S.R. |
By flight |
Luna-2 |
1959 |
U.S.S.R. |
crash |
Luna-3 |
1959 |
U.S.S.R. |
Photographs of hidden side of the moon |
Ranger-7 |
1964 |
The |
Photographs of hidden side of the moon crash |
Luna-9 |
1966 |
U.S.S.R. |
First
landing on the moon |
Apollo-11 |
1969 |
The |
First
manned landing on the moon, return of
samples |
Luna-16 |
1970 |
U.S.S.R. |
Automatic return of
samples |
Luna-17 |
1970 |
U.S.S.R. |
Lunokhod-1:remote
controlled moon jeep |
III - PHYSICALS CHARACTERISTICS
Position: |
- single Natural satellite
of the Earth |
Movement around the Earth: |
- average distance to the Earth is of 384400km
is approximately 0.0026 A.U. -
orbital Eccentricity: 0.054° - Period of revolution: 27.32 days - Slope of the orbit: 5.1° in comparison with the Terrestrial
orbit |
Rotational movement: |
- the period of rotation of 27.32 days is the
same one as its period of revolution - relative flatness is 0.0006 - slope of the equator compared to the
orbit: 2.6° |
Mass, size and density: |
- equatorial diameter: 3476 km - volume:
2.20*10-3 km2 - mass:
7.35*1022kg - fields gravitational: 1.57N/kg - escape velocity: 2.4km.s-1 - true density: 3.36 - decompressed density: 3.35 - gravity has the equator 1.62m.s-2 |
Temperature on the surface: |
- extreme:
day : 127°C (400K) night : -173 °C (1OOK ) - average:
0°C ( 273 K ) |
Albedo: |
-0.07 |
Atmosphere: |
- none |
Magnetic field: |
- none |
Tourist information: |
- time of radio transmission with the Earth is
of approximately 1.3s |
Tides
count among the most significant variations In the height of the sea. The
combined attraction of the Moon and the Sun, is at the origin of this
phenomena and its variations. The
Moon and the Sun attract the Earth and its oceans which become deformed.
Water will accumulate
where attraction is maximum, i.e. at the point
of the sphere located closest to the star. Moreover,
thanks to the speed of movement, a centrifugal force opposite to attraction
maintains the Earth on its orbit. This centrifugai force pushes back the
water, which thus will accumulate contrary to the Star.
Moreover, one knows that the Moon is seldom in the equatorial plan of the
Earth, thus, for the same latitude,
the amptude will not be the same for the two daily tides. Sometimes there is only one
tide per day. |
from”
Astronomie et astrophysique” |
Titan, the greatest satellite of Saturn, is very
interesting because it can be compared to Earth at this origin.
The atmosphere is very rich, actually scientists
suppose that consists of clouds of ammoniac, nitrogen and methane or could say
“among over grasses”. They are waiting with impatience the landing of the
Huygens spacecraft.
We can note that diameter and mass are similar at the
moon but the principal difference is about atmosphere. The atmosphere of Titan
is very important with organic molecules like N2 and CH4.
Principals characteristics of Titan and comparison
with moon :
Datas |
|
Comparison
with M oon |
position |
1 222 000
km from Saturn |
3,2 x
distance Earth- Moon |
Period
of revolution |
15,96
days |
27,32
days |
diameter |
5150 km |
1,48 x |
volume |
7,2.1010
km3 |
3,3 x |
mass |
1,3.1023
kg |
1,77 x |
Density |
1,9 |
0,57 x |
Atmosphere -
pressure -
temperature -
composition |
1,5 bar - 183
°C ( 90 K ) 90% of
N2 ; 10% of CH4 ; clouds of hydrocarbures |
None - 173
°C ( 100 K ) none |
albedo |
0,2 |
0,07 |
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This image
taken by Cassini's visual and infrared
mapping spectrometer clearly shows surface features on Titan. It is a
composite of false-color images taken at three infrared wavelengths: 2 microns
(blue); 2.7 microns (red); and 5 microns (green). A methane cloud can be seen
at the south pole (top of image). This picture was obtained as Cassini flew
by Titan at altitudes ranging from 100,000 to 140,000 kilometers (88,000 to
63,000 miles), less than two hours before the spacecraft's closest approach.
The inset picture shows the landing site of Cassini's piggybacked Huygens
probe. Credit:
NASA/JPL/University of Arizona |
VI- Experiments
After preparatory meetings we chose the evening of October 21, 2004 to take our
images. All the photographs were taken by us with the assistance of a
professor of the club of astronomy. This evening
was not selected randomly, because to make a good lunar study in the evening,
we needed to take pictures during the first quarter, while having a clear
sky. This evening was “ideal”. After having gathered the material in the course of
the day, we began the evening at 19h00. After installing the material, we
could begin the observation from 19h18. With material of a Perl Vixen
refractor 150mm in diameter and 750mm focal distance, we observed the Moon.
The webcam “toucam pro” was used to carry out the videos, several
intermediaries were used, like the lens of Barlow 2X, a reducer of focal of
0.5X, a filter cantiniuum or a IR-UV filter, (it cuts infra-red and
ultra-violet at the same time). |
Pierre
and the telescope |
We encountered several difficulties that evening. Given that this refractor is equipped with a motorised
mounting aided by automatic follow-up, we first had to mount it, that is align
the refractor’s axis of rotation with the earth’s. During the first
observation we experienced a lot of turbulence which complicated the
focusing. We also realised that focusing produced vibrations which were
accentuated by the refractor zoom. Thus, the more we zoomed, the stronger the
vibrations were (use of barlow). Furthermore, the wind created vibrations on
the refractor. The turbulence was therefore stronger because, the moon being
low caused the atmosphere to be thicker. |
Webcam
and this carry-eyepiece adapter |
We produced a score of films of the moon that required
formatting in order to be released. The formatting For this step we used a program called “registax
V1.1beta” which is free and available on the internet. Formatting at a film
file-type.avi is carried out in 4 stages:
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2 - Observations
At the time of our
observation, we could notice that there were various kinds of craters. Some have a central peak located at the center
of the crater, others have their crown in the shape of steps, others have an extremely flat bottom... All these differences let suppose that all
these craters have many different origins.
Thus we will raise some assumptions, which we will explain thereafter by
comparing the results of our experiments with the craters of the Moon that we
took.
We have observed that the
moon crater could have various forms shown on this photography:
(Personnal picture)
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On the small and the large
craters (fig. 1 and 2 ) diameter d is
close to the diameter of its base D.
Moreover, on the craters on fig. 1 and 2 the diameter is much larger
than their height. One can notice that the
crater on fig.2 has one central peak, they are not found only on craters of a
significant diameter. We noticed that some of the
craters had an extremely flat bottom whereas with other are equipped with an
irregular bottom. |
We also observed long
mountainous bands, those would be the vestiges of old giant craters (dating
from the formation of the Moon) having been immersed by the magma resulting
from the lunar era of vulcanicity (= 3.3 Gy).
They are the seas. Some finals images after treatments : ( pictures took by us ) |
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3 -
Assumptions
The lunar craters can have
different origins. That is seen by the
diversity of their forms. Here are some assumptions concerning their origin:
1 - Volcanic origin: flow of lava produced by the repression of a
dome, which is dug by the aspiration of the magma.
2 - Meteoritic origin: fall of meteorites which by contact on the
lunar ground disintegrated by producing a violent explosion devastating a
surface much larger than the size of the meteorite itself.
3 - Collapse: once the era of vulcanicity was completed,
certain bulky magmatic chambers could have been blocked causing a very
significant local collapse. That would
result in a considerable drop of the level of the lunar ground.
These various assumptions are
the fruit of our imagination. Some can appear
more realistic than others. We will
model thus them and observe their result in order to roughly deduce the origin
of the various lunar craters.
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The first experiment consisted in reproducing on a
small scale the formation of a crater of volcanic origin. For that we used a polystyrene container (~
8 L) which we equipped with a PVC pipe that we heated to give it a U shape
(fig. 1). We then ran concrete in this
container up to the level of the head of the pipe, and then we let it dry for
about two days. Observations: we
obtained a crater of a very small raised diameter, broad, without jagged
edges. |
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The second experiment
consisted in modelling the fall of meteorites and observing the results. To
be done, we had to copy of the lunar crust in a container. We then used plaster which we dampened so
that it had an ideal consistency:
neither too soft, nor too hard, to be closest to the surface of the
Moon. Once the good compromise was
found, we manufactured pellets of this plaster, of the same consistency, in
order to copy on a reduced scale the meteorites. We then propelled them against the plaster
surface contained in the container and at this point in time some craters of
various forms appeared. |
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Observations: We
obtained craters of various aspects but on the whole they have shredded
edges, a low depth compared to the diameter and a bottom without a central
peak. |
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The third experiment consisted
in reproducing the effect of the collapse of an underground cavity (ex: old lunar magmatic chamber). For that, we used dry plaster with the
consistency of corn flow again in which we put an inflatable balloon fitted
with a valve than enable us to inflate and deflate it at will. |
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Observations: we obtained
flat-bottomed circular cavities, but without raised edges |
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Experimental modelling to which we carried out have us
to deduce the probable origin of certain craters: smallest.
Indeed, those whose extreme
diameters (bases and head of the crater) are almost equal and the height is
low. Their characteristics observed with
the telescope correspond to the characteristics of the craters modelled in our
experiment. They are small craters which
are also the most widespread on the lunar surface.
The large craters with
central peak were very difficult to model.
We were not able to produce one in our experiment. Was this the result
of the consistency of our model not corresponding to the consistency on the
lunar ground? Or perhaps an insufficient
launch speed? Is our modelling adapted
on a great crater scale?
In the same way, to come up with a crater "of
volcanic origin", we modelled a dome with a central hollow (fig 1). Would this be the cause of a bad consistency of
the material, or is because the retractation of cement is different from the
lunar magma?
As for the craters whose origin would be a collapse, our experiments
give only extremely cylindrical craters of which the depth varies according to
the volume of the balloon after inflation.
We can think that on a large scale, a collapse would
produce strong vibrations which would cause crumbling of the walls of the
craters. The final result would be a crater in the shape of steps with a more
or less conical total form
(fig 2).
The results of these experiments are rather
disappointing because they can explain only one kind of craters: those of
modest size. But the difficulty of modelling these phenomena in addition
teaches us difficulties to model and the importance of the side effects of
these phenomena (vibrations) and all their details to be taken into
account.
We find this experiment to
be harder than expected, but very interesting nonetheless. It enabled us to
discover more about the mysteries of our satellite, the Moon. As the project went on, our
problems multiplied. However, we were not discouraged. The fact that this was
such a challenging experiment made the results we achieve through our
experiments all the more satisfying. First of all, producing the
images proved rather difficult. Even though we experienced good weather, the
unfortunate presence of turbulence made it hard to take clear picture. We are
therefore very proud of our images. They took a long time to take because we
had to make many attempts before we succeeded. |
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Bibliography :
« astronomie et astrophysique » Seguin et Villeneuve.
« astronomie et webcam » Christophe Béthune.
Internet sites :
http://www.r.aberlin.free.fr/lune.htm
www.astronomie.caplain.net/lune.htm
www.membre.lycos.fr/solaire/html/sys_solaire/terre/lune/lune.htm
PROJECT REALISED BY:
Group N° 32 |
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CLENET
Antoine ( 18 years ) , DABRETEAU
Pierre ( 17 years ) and
Jean-Jacques RIVES ( teacher ) From :
Lycée Léonard de Vinci Rue du
fromenteau BP 369 85603 MONTAIGU Cedex |
Thanks to
M.GAUTHIER ET Mr Richard for the
help to traduce this document.