  We explore two ways in which objects of planetary masses can form. One is in
disk systems like the solar system. The other is in dense clusters where stars
and brown dwarfs form. We do not yet have the instrumental accuracy to detect
multiplanet systems with masses like those in solar system; with our present
technology from a distant site, only the effects of Jupiter could be detected.
We show that the orbital characteristics (eccentricities and semimajor axes) of
stellar, brown dwarf, and exoplanet companions of solar-type stars are all the
same within our measuring accuracies and are very different than the planets in
the solar system. The period ratios in multiplanet systems do not distinguish
between the two models. We conclude that most of the exoplanets found to date
are formed like stellar companions and not in disk systems like the solar
system. This conclusion explains why metal-poor stars lack planets: because
metal-poor stars lack stellar companions with short periods. The distribution
of exoplanetary periods for primaries having [Fe/H]< -0.3 fits the distribution
for stellar companions of metal-poor stars and not of metal-rich stars.
