Heavy elements are produced by supernovas. Some of
the resulting clouds of hot gases
slowly coalesce, their centers collapsing under gravity to form stars. Somehow parts of
the outer regions of these clouds form planets. How does this happen? |
The standard model involves collisions of successively
larger objects. |
More careful calculations reveal a problem with the
standard model. |
Another model avoids this problem by asserting that instead of small rocks,
fractal dust clumps form. |
|
There is some evidence to support this view. |
Comets are thought to be fossils from
the very early solar system. During the last flyby of Halley, the density was estimated
at about 0.2 gm/cm3 - that is, this comet is not a huge snowball, but rather
is very fluffy, possibly with a fractal structure. |
Many details of this model remain unclear.
In particular, the mechanical properties
of fractal dust is an area of active research. If we observe the sorts of restructuring
necessary to make the transition from cotton ball to planetisimal, then fractals may take
on a very important role in our history. |