SP-345 Evolution of the Solar
System
FIGURE 20.7.1a.- Average density of
planets and former planets as a function of orbital distance rorb
from the Sun. The guideline through the population of density points
is intended for intercomparison of this figure with figs. 20.7.1b and
c. The ordinate is also given in terms of gravitational potential
energy (mass, Mc, divided by
orbital radius, rorb); this makes
it possible to directly compare the distribution of satellites with
that of the planets The gravitational potential energy is also a
parameter which enters in an important manner in the discussion of
the critical velocity phenomenon (see chs. 21
and 23). Since the Moon and Triton are captured planets, the
Sun is regarded as their central body. Hence the Moon and Triton have
the approximate gravitational potential energy of the Earth and
Neptune, respectively. The horizontal lines through the points for
Ceres, Vesta, Triton, and Pluto indicate the estimated range of
uncertainty, with the vertical bar designating the lower limit for
the density of Pluto as discussed in the text. Data from table
20.5.1.
- Back -