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again,
but
sometimes
they
fall
into
a
long
orbit
aroundthe
sun.
about
three
or
four
of
these
a
year,
known
as
long-period
comets,
pass
through
theinner
solar
system.
just
occasionally
these
stray
visitors
smack
into
something
solid,
likeearth.
that’s
why
we’ve
come
out
here
now—because
the
comet
we
have
come