*Astron. Astrophys. 346, L65-L68 (1999)*
## 4. In the long run
Asteroid 1999 AN_{10} was observed until the angular
distance from the sun became . It
will be again at from the Sun after
the beginning of June; by that time the uncertainty of its position on
the sky will grow to 1.5 arc minutes (corresponding to
), that is any new observation will
significantly contribute to an improvement of the orbit. It is very
likely that the observations made in the second half of this year will
constrain the orbit well enough to predict accurately the 2027
encounter. This implies that some of the returns of the Table will be
discarded as incompatible with the observations; in fact, most of them
if the 2027 encounter is not very deep.
The problem, however, will not go away, because all along the LOV
there are possible encounters occurring later, almost every six
months. We have analysed with our global method the same
multiple solutions over a time span
of 50 years after 2027, and found 165 possible returns, out of which
117 in the moderate to low stretching region. This situation is
qualitatively stable: whatever the actual orbit is, it will not be
possible to predict with certainty the returns after the next close
approach for a time span longer than a few decades.
Since at least one node of 1999 AN_{10} will remain
close to the orbit of the Earth for centuries, this asteroid shall
have to be monitored, by observations and computations, for a very
long time. It is conceivable that at some time in the future a
decision could be made to deflect it; but, a deflection decreasing the
depth of some specific close approach could increase the impact risk
at a later date. Thus before such a decision can be contemplated we
need to better understand the theory of resonant and non-resonant
returns, which has only been outlined in this paper.
© European Southern Observatory (ESO) 1999
Online publication: June 17, 1999
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