  Motivated by the trends found in the observed sample of extrasolar planets,
this paper determines tidal equilibrium states for forming planetary systems
--- subject to conservation of angular momentum, constant total mass, and fixed
orbital spacing. In the low-mass limit, valid for superearth-class planets with
masses of order $m_{\rm p}\sim10M_\oplus$, previous work showed that energy
optimization leads to nearly equal mass planets, with circular orbits confined
to a plane. The present treatment generalizes previous results by including the
self-gravity of the planetary bodies. For systems with sufficiently large total
mass $m_{\scriptstyle T}$ in planets, the optimized energy state switches over
from the case of nearly equal mass planets to a configuration where one planet
contains most of the material. This transition occurs for a critical mass
threshold of approximately $m_{\scriptstyle T} \ge m_{\scriptstyle
C}\sim40M_\oplus$ (where the value depends on the semimajor axes of the
planetary orbits, the stellar mass, and other system properties). These
considerations of energy optimization apply over a wide range of mass scales,
from binary stars to planetary systems to the collection of moons orbiting the
giant planets in our solar system.
