The Deviation of the Lunar Center of Mass to the East of the Direction Toward the Earth. A Mechanism Based on Orbital Evolutionстатья
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Дата последнего поиска статьи во внешних источниках: 11 сентября 2018 г.
Аннотация:Abstract
—
It is known from observations of the gravitational
fi
eld and
fi
gure of the Moon that its center
of mass (COM) does not coincide with its geometric center, with the line connecting these two points
deviating to the Southeast of the direction toward the center of the Earth. The deviation of the lunar COM
to the South was explained earlier. Here, the deviation of the lunar COM to the East of the direction toward
the Earth is considered. The theory of the optical libration of a satellite orbiting synchronously about a
planet for an observer at the secondary (free) focus of the orbit is
fi
rst re
fi
ned. It is shown that the main axis
of inertia of the satellite undergoes asymmetric, non
-linear oscillations whose amplitude is proportional
to the square of the orbital eccentricity. A mechanism for the evolution of the orbit has been developed,
taking into account the preferred direction of the axis of inertia of the Moon toward the empty focus. Of
two alternative scenarios
—
evolution of the lunar orbit with decreasing or increasing eccentricity
—
only the
latter scenario is consistent with the observed eastward shift of the lunar COM. This mechanism predicts
that the lunar orbit had a lower eccentricity in the pas
t than it does today. This conclusion is consistent
with the results of observations and also with the fact that the eccentricity of the Moon’s orbit is indeed
currently increasing, indicating that it was lower in the past than its current value,
e
=0
.
0549
.Itisshown
by averaging the motion over a rapid variable that this mechanism for the orbital evolution can explain about
18
%
of the currently known eastward shift of the lunar COM. The results obtained re
fi
ne the theory of the
tidal evolution of the Moon.