Mikael Granvik, Jeremie Vaubaillon, Robert Jedicke
We have for the first time calculated the population characteristics of the
Earth's irregular natural satellites (NES) that are temporarily captured from
the near-Earth-object (NEO) population. The steady-state NES size-frequency and
residence-time distributions were determined under the dynamical influence of
all the massive bodies in the solar system (but mainly the Sun, Earth, and
Moon) for NEOs of negligible mass. To this end, we compute the NES capture
probability from the NEO population as a function of the latter's heliocentric
orbital elements and combine those results with the current best estimates for
the NEO size-frequency and orbital distribution. At any given time there should
be at least one NES of 1-meter diameter orbiting the Earth. The average
temporarily-captured orbiter (TCO; an object that makes at least one revolution
around the Earth in a co-rotating coordinate system) completes
$(2.88\pm0.82)\rev$ around the Earth during a capture event that lasts
$(286\pm18)\days$. We find a small preference for capture events starting in
either January or July. Our results are consistent with the single known
natural TCO, 2006 RH$_{120}$, a few-meter diameter object that was captured for
about a year starting in June 2006. We estimate that about 0.1% of all meteors
impacting the Earth were TCOs.
View original:
http://arxiv.org/abs/1112.3781
You find a "small preference for capture events starting in either January or July." 500 yrs ago, would the preference still have been Jan or Jul? In other words, what causes this preference? Thank you,
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