FREE ESSAY ON ORIGIN OF SOLAR SYSTEM

ORIGIN OF SOLAR SYSTEM

The Origin of the Solar System One of the most intriguing questions in astronomy today is
the how our solar system formed. Not only does the answer add insight to other similarly
forming systems, but also helps to satisfy our curiosity about the origin of our species.
Although it is highly unlikely that astronomers will ever know with absolute scientific
certainty how our system originated, they can construct similar theoretical models with
the hopes gaining a better understanding. A basic understand of the current physical
aspects of our solar system are helpful when trying to analyzing its origin. Our solar
system is made of the Sun, nine major planets, at least sixty planetary satellite,
thousands of asteroids and comets that all span an immense distance. Each planet has its
own individual characteristics and seven of which have one or more satellites. There are
thousands of asteroids, mainly congested in the area between Mars and Jupiter, as well as
countless comets that all travel in a spherical orbit around our Sun. The Sun contains
approximately 99 percent of the mass in the solar system, but only 2 percent of the
system's angular momentum. It lies in the center of our system while all planets,
asteroids and alike rotate in elliptical orbits around it in the same plane. The smaller
inner planets have solid surfaces, lack ring systems and have far fewer satellites then
the outer planets. Atmospheres of most of the inner planets consist of large quantities
of oxidized compounds such as carbon dioxide. While on the other hand, the outer planets
are far more massive then the inner terrestrial planets, and have gigantic atmospheres
composed mainly of hydrogen and helium. Asteroids and comets make up the smallest portion
of the solar systems entities and are composed of the remnants left behind while planets
were forming. For over 300 years, there has been a very long history of conjecture on the
origin of the solar system. These many theories stem from two general categories. The
first category called monistic, involves the evolution of the Sun and planets as an
isolated system. The second group of theories called dualistic, suggested that the solar
system formed as a result of the interaction between two individual stars. The dualistic
formation theory has been almost entirely dropped and monistic formation has become the
general consensus on the basic formation of our solar system. Most modern theories of the
origin of the solar system hypothesize that all bodies in the solar system, including the
sun accreted from the formation and evolution of a single primordial solar nebula. It is
believed that our solar system began to form around 4.56 billion years ago from a dense
interstellar cloud of gas. Because of the conservation of angular momentum, the cloud of
gas formed a rotating flattened disk approximately the size of the planetary system. It
was this flattened disk that is referred to as the primitive solar nebula and from which
our current solar system evolved. Ordinarily, the internal pressures of the cloud are
sufficient to prevent if form collapsing. However, from time to time local increases in
pressure of the interstellar medium cause the additional compression of interstellar
clouds. These compressions caused the clouds to reach their threshold of gravitational
collapse. Once the gravitational attraction of matter is greater then any tendency to
expand due to internal pressures the cloud begins to collapse inward. Theoretical models
suggest that the presolar nebula continued to collapse until the center of the cloud
became so dense that heat started to form. This heat increased the thermal pressure of
the cloud until the collapse was eventually halted. The existence of our system of
planets is entirely due to the angular momentum of the initial cloud. If there were no
angular momentum, then the interstellar cloud would have collapsed to from a single star.
While at the same time, if the collapse had occurred under a system with too much angular
momentum then a binary star would have resulted from our system. Our system formed under
intermediate conditions allowing the planets to evolve. The fact that the Sun contains 99
percent of the solar system's mass but only 2 percent of its angular momentum raises
questions about the distribution of masses during the early formation of the solar
system. It is suggested that certain processes transported nebula mass inward to form the
Sun, and angular momentum outward to the preplanetary region. Thus decreasing the total
angular momentum of the Sun. Three separate hypothesizes have been suggested to explain
the processes for such a transport. The main theories suggest that gravitational torques,
viscous stress, and magnetic fields may have acted individually or in some combination to
produce our present system. The first theory including gravitational torques arises from
the gravitational forces between segments of asymmetric mass. One example of this case
would be between inner and outer regions of the trailing spiral arms of the nebula.
Assuming there is a source of asymmetry, then these torques can result in significant
outward transportation of angular momentum. Viscous stresses are another possible source
of the shift in angular momentum of the solar system during its evolution. Viscous
stresses are caused by the friction between adjacent fluid parcels trying to move past
each other with different speeds. These stresses result in the outward transport of
angular momentum and are one more possible explanation to the outward spread of momentum.
The third theory postulates that magnetic fields are the source of this momentum
transfer. Magnetic fields may have been produced during the collapse of the initial cloud
or even electrically generated between the proto-Sun and the solar nebula. This would
eventually end in the same result of an outward spread of angular momentum. Therefore the
evolution of the solar nebula involved both the transportation of mass into the central
proto-Sun region and the increased angular momentum in the planetary regions. This meant
that most of the primitive cloud's mass fell in to the proto-Sun's region while the
remainder formed the planets. It is not only important to study the evolution of the
solar nebula, but also the formation of the planets. There is a general consensus that
once the solar nebula settled to rest that solid dust particles began to move toward the
central plane of the nebula. It was at this stage that the planets began to form. There
are two current theories that resulted in the development of the planets. The first
theory suggests that the planets formed in a very basic process where dust particles
accumulated into planetesimals which in turn grew to the present planets. The second
theory proposes that planetesimals resulted from a gravitational instability in the
gaseous portion of the solar nebula. The first theory states process of planet formation
began with the settling of dust in into the central plane of the nebular disk. Soon
after, the first dust particles began to coagulate into small solid bodies. These bodies
then accumulated through a collective gravitational instability in of the dust disk. The
thin dust disk became more massive through continual sedimentation and resulted in its
breakup into a large number of planetesimals. Through a process of random collisions
these planetesimal continued to grow and accumulate mass. There are two possible extremes
that ended this process of accumulation. The first involved runaway accreting where one
object grows extremely large through the collection of all smaller planetesimals within
its area. The alternative extreme would involve the uniform growth of a number of masses
resulting in a many equal mass planetesimals. It is currently believed that the formation
of the planets resulted from a combination of these two processes. The equal mass
accumulation is presumed to have dominated during the early stages of planet formation
while the run away accumulation is suggested to have taken over during the latter stages.
However, there is one substantial problem with this explanation of the planet's
formation. The accumulation theory fails to take into account the rapid formation of the
giant planets. By the slow process of coagulation, it would take much longer then the
lifetime of the solar system to form the giant planets of Jupiter and Saturn. This
incorrectness in the first theory led scientists to contrive the second theory. The
second theory of planetary evolution involves a gravitational instability of the gaseous
portion of the solar nebula. It is suggested that if the solar system were massive enough
then the instability would lead to the fragmentation of the gaseous nebula and the
formation of giant gaseous protoplanets. This theory allows plenty of time for the
formation of the very large planets Jupiter and Saturn. The one flaw of this theory is
its contingency on a very massive planetary nebula, one much larger than ours. Because of
this problem many cosmogonists have begun to doubt that the gaseous disk instability led
to planet formation in our solar system. Although many of the details on the theories of
our solar system will most likely change in the near future, the fundamental concept of
solar system formation appear to remain the same. The Sun and planets began forming
approximately 4.56 billion years ago out of a solar nebula produced by the collapse of a
rotating interstellar cloud of gas and dust. Following soon after, the terrestrial and
Jovian planets eventually formed from the collision and accumulation of smaller
planetesimals. While there is significant evidence supporting the formation of the Sun
and planets in this way, it is not likely that scientist will know with complete
certainty about the solar system's origin for some time. It is highly likely that the
details in the theory of the solar system will change. With continued improvements in
technology and significant advances in astronomical fields of observation, further
understanding of our solar system will undoubtedly come. In recent years, the idea that
the Solar System formed from the evolution of a primodial solar nebula, has received
significant conformation. The use of satellites such as the Infrared Astronomical
Satellite (IRAS) have detected disks of solid particles around several nearby stars,
including Formalhaut, Beta Pictoris and Vega. The uses of satellites have provided
scientists with most of the information they currently have on the system's origin.
Another source of information lies in our neighboring planets. Investigations of the
other planets in the solar system by means of interplanetary spacecraft have provided a
wealth of data pertaining to the origin and history of the solar system. Through the
observation of solar-type stars in the Galaxy, we can learn critical information about
the properties of the interstellar cloud that collapsed to form our own solar nebula. It
is likely that future explorations and observations will help to solidify our
understanding of the solar system.