100-C 25-C 50-C 75-C C+M 50-C+M C+Y 50-C+Y M+Y 50-M+Y 100-M 25-M 50-M 75-M 100-Y 25-Y 50-Y 75-Y 100-K 25-K 25-19-19 50-K50-40-40 75-K 75-64-64CHAPTER 2
The Origin of the Solar
System
John E. Chambers
Carnegie Institution of Washington
Washington, D.C.Alex N. Halliday
University of Oxford
Oxford, United Kingdom- Introduction 7. The Asteroid Belt
- Star Formation and Protoplanetary Disks 8. Growth of Gas and Ice Giant Planets
- Meteorites and the Origin of the Solar System 9. Planetary Satellites
- Nucleosynthesis and Short-Lived Isotopes 10. Extrasolar Planets
- Early Stages of Planetary Growth 11. Summary and Future Prospects
- Formation of Terrestrial Planets Bibliography
1. Introduction
The origin of the solar system has long been a fascinating
subject posing difficult questions of deep significance. It
takes one to the heart of the question of our origins, of how
we came to be here and why our surroundings look the way
they do. Unfortunately, we currently lack a self-consistent
model for the origin of the solar system and other planetary
systems. The early stages of planet formation are obscure,
and we have only a modest understanding of how much the
orbits of planets change during and after their formation. At
present, we cannot say whether terrestrial planets similar
to the Earth are commonplace or highly unusual. Nor do
we know the source of the water that makes our planet
habitable.
In the face of such uncertainty, one might ask whether
we will ever understand how planetary systems form. In
fact, the last 10 years have seen rapid progress in almost
every area of planetary science, and our understanding of
the origin of the solar system and other planetary systems
has improved greatly as a result. Planetary science today
is as exciting as it has been at any time since theApollo
landings on the Moon, and the coming decade looks set to
continue this trend.
Some key recent developments follow:
1.A decade ago, the first planet orbiting another Sun-
like star was discovered. Since then, new planets have
been found at an astounding rate, and roughly 200 ob-
jects are known today. Most of these planets appear
to be gas giants similar to Jupiter and Saturn. Re-
cently, several smaller planets have been found, and
these may be akin to Uranus and Neptune, or possibly
large analogs of terrestrial planets like Earth.
2.In the last 10 years, there have been a number of
highly successful space missions to other bodies in
the solar system, including Mars, Saturn, Titan, and
several asteroids and comets. Information and images
returned from these missions have transformed our
view of these objects and greatly enhanced our un-
derstanding of their origin and evolution.
3.The discovery that one can physically separate and an-
alyze star dust–presolar grains that can be extracted
from meteorites and that formed in the envelopes of
other stars—has meant that scientists can for the first
time test decades of theory on how stars work. The
parallel development of methods for extracting iso-
topic information at the submicron scale has opened