Limits on the abundances of heavy elements in the four jovian planets
in our Solar System. For each planet, the point on the left represents
the total amount of high-Z material, whereas the (lower) point
on the right shows 
the amount of heavy
elements segregated into the planet's core.  For Jupiter and Saturn, the
thick lines represent solutions with additional constraints obtained
from evolution models. Note the high level of uncertainty, especially
regarding the core masses of Jupiter and Saturn. Models of Jupiter
with small cores (i.e., less than 2 Mearth) require significant
enrichments in heavy elements (i.e., more than 20 Mearth).
(From Wuchterl, Guillot & Lissauer 2000; PPIV)