May Have Been Captured In "Close" Encounter
Recently, astronomers reported the surprising discovery of a
very large diameter Kuiper Belt planetoid -- (90377) Sedna -- on a
distant, 12,500-year-long, eccentric orbit centered approximately
500 astronomical units from the Sun. Sedna's estimated diameter is
about 1,600 km, two-thirds that of Pluto. Initial studies of
Sedna's origin have speculated that it might have been ejected from
the giant planets region of our solar system far inside the orbit
of Pluto, or perhaps was captured from a passing star's Kuiper
Belt.