Category: Solar System

Introduction

The early astronomers considered the sun, stars, and planets to be the only components of the entire universe. They had a strong belief that the Earth was the heart of the whole creation. They also realized that stars’ position did not change and that there were other star-like objects as well, wandering amid them.

They called the star-like objects; planets, which is a Greek word for “wanderers”. During the early 1500’s, the first astronomer Nicholas Copernicus in a controversial statement asserted that the sun was the center of the solar system, and not the earth. This was not popular with the people and although his ideas were unpopular, he is the father of modern astronomy. Galileo Galilei came later as the first astronomer to study the planets using a telescope (Kruesi 16).

Astronomers have with a lot of effort tried to find an answer to the original place of formation of asteroids and comets. As late as mid twentieth century, the well-known theory alleging that asteroids are leftovers of an ancient planet flare-up, still existed. A number of astronomers even believed that majority of these asteroids were situated in the asteroid belt that is located amid Jupiter and mass (Ipatov).

On the other hand, they assumed that comets were hanging groups of pebbles and sand that had gathered and were just moving about haphazardly all through the solar system. The idea was that if one of those substances drew near a planet, the bigger body’s magnitude pulled the comet in the direction of the inner solar system where Venus, Earth, Mars, and Mercury inhabited (Brownlee 32).

Origin of Asteroids and Comets

Due to lack of a clear theory or explanation as to the origin of comets and asteroids, scientists had to seek explanations from diverse outlooks in an effort to give details on the beginning of the solar system. Scientists discarded the previous notion that asteroids originated from an explosion of a planet that was situated somewhere stuck between Jupiter and Mars.

This is because the whole mass of entire bodies uncovered in the asteroid belt could not yet amount to a minute portion of the Earth’s mass (Brownlee 30). The modified conclusion came to be, that the asteroid belt does not contain adequate collection to structure a whole planet.

Similarly, it was later observed that asteroids are also located in other segments of the solar system apart from Mars and Jupiter. Through this attempt of giving an explanation on how the asteroids might have left the asteroid belt, an enhanced perspective of their formation was apprehended (Ipatov and Mather 1530).

A better perception of what comets actually are and how they were possibly formed came to existence. This is attributed to a number of researchers who drew attention to the reality that the previous theory on floating sandbank was insufficient, given that it was unsuccessful in explaining how a comet possibly will repetitively structure a tail during every visit to the inner solar system (Brownlee 31).

Originally, there was an assumption that sand grains creating a comet had an ice coating that melted as the comet drew nearer to the sun and the ensuing vapor figured the tail. Consequent reviews to this theory came up with a conclusion that only a single trip to the inner solar system would exhaust the entire ice. In great efforts to discover how the solar system was created, astronomers reassessed the theory of how comets were formed, with a belief in mind that icy bodies might have just formed in particular regions (Kruesi 16).

Solar System Formation

Ultimately, it is the reworked theory of formation of comets and asteroids that finally appeared to fit precisely and rationally in the larger model developed before by scientists to give details on how the complete solar system might have formed. This bigger model was put forward from the solar nebula premise initially proposed in the 18^th century through French mathematician Pierre-Simon Laplace and German philosopher, Immanuel Kant (Ipatov).

In this contemporary theory, it is projected that the development of the solar system was about 4.5 to 5 billion years back, as a result of a vast cloud of dust and gases floating all over the space. The majority of these substances were extremely and incredibly thin dispersed, although they still put forth considerable gravitational pull.

Because of this gravitational force, particles of both dust and gas were forced to move in the direction of one another. Additional materials continued falling headed to the center of the nebula as the process went on. The heavier the core developed in mass, the higher the gravitational force it produced (Ipatov).

Due to the fact that a rise in gravitational pull leads to extra materials being attracted to the core and while the mass with gravitational pull amplified, the process gathered speed even further. The course of activity of falling materials to the center of the core, led to resistance so the majority of the energy escaped inform of heat that caused the inner elements of the planet to warm up.

This growth of the amplified mass and the relative rise in heat within the core increased so immensely that the heats build up at the center of the mass could not escape any further. This led to a nuclear reaction and the ultimate formation of the sun (Brownlee 32).

This contemporary theory therefore suggests that the residual materials since the first cloud, came together to structure a compacted disk that rotates around the sun. Scientists believe that the flat disk of objects was the beginning of the planets, asteroids, comets, and moons.

The elements of the enormous disk that were far-off the hot star rapidly began cooling down and finally coagulated into elements of ice and rock. Then, due to gravitational force, the particles were stuck close to each other and therefore forming bigger particles and ultimate huge bodies many thousand miles in diameter called planetesimals (Ipatov and Mather 1526).

Planetesimals were believed to contain loose granular-like structures, enabling them to absorb energy from whichever object that knocked them hence thwarting them from bouncing back yet again. A gathering of numerous big planetesimals led to the creation of planets and moons, whereas analogous accumulations of lesser planetesimals came up with formation of comets and asteroids (Rice 48).

Asteroid Belt

The crucial departure points of asteroids and comets in the early solar system could stem from the type of materials that made each one of them, in addition to the distance of each one of them from the sun. The planetesimals formed near the inner solar system contained harder material since they were more directed to the hot sun and therefore became heat-resistant.

Nearly all the materials that endured this sort of heat were iron and heat defiant rocks. Owing to the regular friction and the gravitational pull emanating from superior bodies, a number of the rocky and metallic planetesimals were finally integrated into the bodies of the central planets (Rose 56).

On the contrary, the hard planetesimals situated on the outer surface of the inner solar system, that is, beyond Mars, possibly could not collect to structure a planet. This could be due to the fact that they were very close to Jupiter, which being the leading planet in the whole solar system, applied an extremely powerful gravitational pull keeping majority of the objects, from gathering to make a single huge planet (Rice 50).

Consequently, a good number of the planetesimals stayed separate. This might be confirmed in the sense that the asteroids are experiential as existing in an orbit that ought to have been taken by a planet therefore leading to the verity that earthly pattern projected by Titius-Bode Law could be right (Rose 56).

Asteroid belt was a tumultuous and vicious region because particles were hauled towards one another via their gravitational pull and the sturdy Jupiter’s gravity. Scientists as a result suggested that it is impossible for millions of bodies to go on floating eternally in the asteroid belt (Kruesi 16).

The main feature that always interrupts these bodies is the shock that originates from recurring collisions. The majority of the asteroids fabricated from the ordinary lab material would be anticipated to collapse as indicated in a variety of laboratory experimentations although every asteroid amid an interconnected strength greater than iron’s is very likely to stand such collisions (Kruesi 16).

The Kuiper Belt

Following the reasoning, that Jupiter’s strong gravity is responsible for the expulsion of asteroids from the asteroid belt, several questions have been asked regarding to where the steroid disappeared to after expulsion. Some scientists argue that some of the asteroids might have penetrated the inner solar system with the likelihood that they could have crashed with either the Sun or the interior planets (Brownlee 33).

Some of the other bodies might have been subjected to never-ending wandering all along the “Interstellar black gulfs space” (Brownlee 33). Another group could possibly have been established in the outer solar system, amid a key argument that Jupiter’s sturdy gravity might have enforced them in the direction of a belt of substance that lies past the major orbits of Uranus, Saturn, and Neptune (Ipatov and Mather 1526).

However, it is important to note that the largest part of materials in this area is not mainly composed of stony and metallic materials but, relatively extra icy (Ipatov and Mather 1528). Located outside the Neptune planet, the belt is at times viewed as a reservoir in which a number of planetesimals go in coming up with a cold region a distance from the sun.

In the process of the said formation of the early on planetesimals, the heat in the inner solar system was too much for ice-based composite to endure and remain intact, resulting to a large number of them being blown outwardly (Brownlee 34).

Temperature at the distant ends were low thus enabling ice-made compounds to withstand. This in turn resulted to a buildup of gases such as ammonia, carbon dioxide, and water ice among others on the external section of the solar system. While there could have been sufficient materials that led to formation of small planetesimals, it was not possible to form the main planets during this span of time and instead formed a merely diffused precinct of quite a few icy objects (Rice 51).

This presence of an icy belt lying past Neptune was established recently by scientists although, it was previously proposed by two researchers; Gerard Kuiper and Kenneth Edgeworth. The affirmation that there are reality objects in that region was appreciated in 1992 where the region came to be named Kuiper Belt in respect of Kuiper, while the bodies therein came to be known as ‘Kuiper Belt objects”, or KBOs (Ipatov and Mather 1528).

Pluto

There have been questions seeking answers as to whether Pluto is a giant comet or a planet, considering it is the smallest planet. From the time it was discovered in the early 1930s, Pluto remains to be the planet whose location is farthest from the sun. This classification has held for a long time until recently when some scientists proposed that Pluto should not be regarded as a planet anymore. This is because of the mere fact that it possibly began just as a huge object in the Kuiper Belt (Rose 57).

There is a probability that Pluto was the ever-biggest ice-based planetesimal to form beyond Neptune region. Despite the fact that Pluto is made up of a very thin atmosphere as well as having a satellite which qualify it to be a planet, there are some asteroids that have satellites in their atmosphere as well. Additionally, other large KBOs have also been found out. In 2001, researchers saw “Varuna, 2001 KX 76”, that is about 550 miles diagonally (Brownlee 34).

This object is almost as large as the Pluto’s moon; Charon, moreover considered as a huge KBO. Because of this invention, a larger KBO approximated to be 800 miles across was later found out in 2002, referred to as xQuaoar. Today, hundreds of big KBOs have been discovered, and scientists estimate it to be a small percentage of them as they are approximated to exist in millions to billions (Ipatov and Mather 1528).

The Oort cloud

Comets are not exceptionally found in the Kuiper belt. When the strong gravitational force within Jupiter ejected a number of asteroids from the belt, a mix of gravities of Saturn, Uranus, Jupiter, and Neptune too vigorously expelled millions of planetesimals, which are suspected to have gone to the inner solar system and absorbed by either the sun or the inner planets (Rice, 47).

A good number of the objects are found in the region of comets and quite a few of the asteroids are found past Pluto in the outer solar system. The region was named after a Dutch astronomer called Jan Oort who discovered it in 1940 (Ipatov).

According to estimations, the immature solar system contained comets packing its environs with the Earth’s primeval sky getting numerous dozens of comets (Rice, 53). Most comets collided with the planets, but some effectively used their gravity to land into totally fangled orbits and mostly planets.

Jupiter was the only planet that could have survived at a higher rate. Any other comet close to Jupiter’s gravity could have been plunged into the Oort cloud or forever expelled from the solar system (Rice 49).This process might have carried 500 million years from the formation of the solar system to drain the supply of comet-based materials at a quicker rate according to scientists. Today the process still goes on, but it takes place at an extremely slow rate as a baton of activities of millions of years ago (Rice 50).

Astronomers estimate that “Oort cloud does elongate for approximately ten to one hundred thousand AU from the sun containing millions to billions of icy bodies” (Brownlee 35). Latest approximates have indicated that 2 percent of the entire objects in this region are asteroids made of metal and stone discarded by the huge planets. Repeated collisions between these objects force some to travel far-off the Oort cloud into the inner solar system. Some pass so close to the earth such that they are visible to human eyes (Rice, 53).

Conclusion

From the above discussion, it is evident that the existence of comets and asteroids in the solar system is not the only evidence to the way it was formed, but also the structure shows a lot about the process of formation (Ipatov). The largest planetesimals are supposed to be the present moons and planets, whereas the lesser planetesimals resulted to be the comets and asteroids.

A greater part of the asteroids was created in the asteroid belt. This part consists of rock and metal whereas, the largely ice-based comets were expelled to the Oort cloud and Kuiper Belt (Ipatov). The current position of asteroids and comets can therefore be perceived to be an excellent pointer to the development that captured millions of years to accomplish the formation of the solar system.

Works Cited

Brownlee, Donald. “Comets and the early solar system.” Physics Today 61.6 (2008): 30-35. Print.

Ipatov, S. Migration of Celestial Bodies in the Solar System. (2003) Editorial URSS Publishing Company, Moscow. Print.

Ipatov, S and Mather, J. “Comet hazard to the Earth.” Advances in Research. 33 (2004): 1524-1533. Print.

Kruesi, Liz. “Meteorite holds hints of solar system formation.” Astronomy 39.7 (2011): 16-16. Print.

Rice, Ken. “Building, moving and destroying planets.” AIP Conference Proceedings, 1094.1(2009): 45-54. Print.

Rose, William. “Early solar systems and the formation of massive stars.” AIP Conference Proceedings 713.1 (2004): 55-58. Print.

Introduction

Philosophers and scientists, particularly the astronomers, have been looking for information pertaining to how the universe was formed.

Even though there is no single authoritative model that explains the manner in which the universe was formed, there is one model that satisfies the highest share of astronomers: the nebular hypothesis or model.

The model is not only the most popular but also the one that garners several factual arguments on its accounts for the formation of the universe. The hypothesis dates back to 1734 when Emanuel Swedenborg (Woolfson 1984, p.6) first proposed it.

It dates the formation of the universe back since some 4.6 billion years following the collapse of an interstellar molecular cloud of particles comprising of ice, rock, and dust among others. However, several criticisms were raised on it for a couple of years making it fall out of favour.

One of the central criticisms of the nebular hypothesis rested on its inability to provide an explanation on why the sun lacked angular momentum in comparison with all other planets, which orbit around it (Fogg & Nelson 2007, p.1195). Nevertheless, “now, it is back with a definitive model” (Gomes et al. 2005, p.466).

As from early 1980s, tremendous studies have been carried on young stars. The studies show that young stars are “surrounded by cool discs and gas, exactly as the nebular hypothesis predicts” (Gomes et al. 2005, p.468). This has made the nebular hypothesis to be reaccepted.

Following this validation of nebular hypothesis, this paper finds it ample to describe nebular model of the solar system coupled with the features of solar system that the model explains.

Description of Nebular model of the solar system

According to nebular model of the formation of the universe, the formation of the solar system is inherent to the formation of the stars and planetary disks. The figure below shows fundamentals of universe formation.

Source: (Kokubo & Ida 2002, p.673)

Formation of stars

Stars are believed to have been formed from a giant cloud of molecular hydrogen, which was as big as 300,000 times the size of the sun (Montmerle at al. 2006, p.42). The nebular theory of the solar system approximates that the massive collapsing of the proto-stellar nebulae took place some 100, 000 years ago (Pudritz 2002, p.69).

All nebulas initiate with some angular momentum. A gas is found at the centre of every nebular. Relative to the outer parts, this gas has a lower angular momentum. It undergoes an incredible compression resulting to the formation of a hot core that does not contract.

The core’s mass is lesser than the original mass of the entire nebula (Mohanty, Ray & Basri 2005, p.492). The core constitutes the seed, which, while fully grown, forms the stars. Further collapsing truncates into retention of the angular momentum.

Consequently, “the rotation of the in-falling envelop accelerates which largely prevents the gas from directly accreting onto the central core” (Klahr & Bodenheimer, 2003, p.869). Forcefully, the gas finds its way outwards close to “the equatorial plane of the core, which in turn forms the disk that further accretes onto the formed core” (Klahr & Bodenheimer 2003, p.887).

This makes the core grow magnificently in terms of mass to the extent that it makes up a proto-star, which is very hot. In this particular stage, the in-falling envelope gigantically obscures the proto-star coupled with its disk making it directly invisible (Mohanty, Ray & Basri 2005, p.499).

The proto-star emits a radiation, which is in the order of sub-millimeters or millimeters. Nebular theory classifies these proto-stars as belonging to class zero. However, the luminosity of these proto-stars is ideally very high ranging in the order of 100.

This energy originates from gravitational collapses (Kokubo & Ida 2002, p.666). It occurs because the cores of the proto-stars have not become hot enough to the extent that the process of nuclear fusion can begin.

When the materials forming the envelope proceed falling into the proto-star disk, a stellar object becomes conspicuous. This occurs initially in the region of infrared and in a visible range of electromagnetic spectrum later.

When the proto-star garners enough mass above, about 80 times of that of Jupiter, hydrogen fusion initiates. However, when this mass is lower than this, a brown dwarf object is developed (Mohanty Ray & Basri 2005, p.508).

Development of new stars takes place about 100, 000 years upon inception of the collapse process. The resulting solar system’s objects are classified as class one proto-stars at this level.

During the next stage, the disk gathers the envelope. This results to its disappearance. The resulting proto-star is the T Tauri star. According to Mohanty, Ray and Basri (2005), “the mass of the disk around a classical T Tauri star is about 1–3% of the stellar mass, and it is accreted at a rate of 10^-7 to 10^-9 solar masses per year” (p.505).

A classical T Tauri star has properties such as “emission limes, existence of jets, photometric variability, strong flux, and possession of magnetic activities” (Mohanty, Ray & Basri 2005, p.505).

The formation of the emission lines is owed to the hitting of the star’s surface by accreted gas. This takes place within the magnetic poles. The jets are principally the avenues through which the excessive momentum of the star is lost.

Formation of planetary disks and planetary system

Apart from the formation of stars, another essential concern of the nebular model is to provide an explanation of how the proto-planetary disks are formed. This provides mechanisms of laying the foundation on provision of an explanation on how the entire universe formed, as well as how it continuously evolves.

Nebular hypothesis holds that, under certain circumstances and provisions, instead of disappearance of the planetary disk, it may give rise into a planetary system.

Megeath et al. supports this argument by claiming, “Proto-planetary disks have been observed around a very high fraction of stars in young star clusters” (2005, p.114). An example of formation of a proto-planetary disk in Orion nebula is shown in the figure below.

Source: (Font et al. 2004, p.901)

Disks exist right from the onset of the process of formation of stars. However, in the early stages, it is not possible to view them because of opacity in the environment that surrounds a proto-star. For a class zero proto-star, the planetary disk is immensely hot.

Consequently, inside the disk, many of the volatile materials evaporate leaving behind refractory elements. Therefore, ice can only possibly exist in the outermost part of the disk (Font et al 2004, p.901). Rocky planets are formed in the inner sections of the proto-planetary disks.

In these sections, temperatures are too high to permit condensation of ice coupled with certain other substances to form grains (Sean, Quinn & Lunine 2007, p.67). Consequently, coagulation of grains that are rocky in nature occur leading to creation of planetensimals that are rocky.

In the words of Montmerle et al (2006), the conditions “are thought to exist in the inner 3-4 AU part of the disk of a sun-like star” (p.73). On the formation of the planetensimals from the proto-planetary disks, the process of runaway accretion initiates.

During this process, the planetary body grows such that M^4/3 is directly proportional to R⁴ (Montmerle et al 2006, p.65) where R is the radius of the growing body while M is its mass. When this process is completed, the stages of oligarchic accretion and merger follow respectively. These are the last two stages for the formation of a rocky planet.

Features of solar system explained by nebular solar system

The nebular theory for the formation of the solar system explains the process of formation of a number of features that make up the solar system. They include stars, planets, and asteroids among others.

The theory holds that the universe formed when the interstellar gas molecules that were filled with ice, rocks, and dusts among other particles spontaneously collapsed. This collapse was caused by a turbulence whose aftermath was heating up of these particles making them turn into stars.

Initially, the components that make up the universe were in the form of clouds. A cloud of dust believed to form the solar system by astronomers is shown below.

Source: (Montmerle et al 2006, p.47)

During the solar system formation process, most of these clouds settled at the centre to form the sun. On the other hand, some of the materials became flattened to form the planetary disks (Montmerle et al 2006, p.49). Material making up the disks formed the planet coupled with other objects that are found in the solar system.

Other materials stuck together to form solids (balls), which grew bigger when more materials collided with them. The balls formed the cores of the planets.

When the growing solids developed their own gravitational pulls, the rate of attraction of ice and dusts particles became even more enhanced.

Stars and terrestrial planets

With regard to the nebular hypothesis, stars resulted from the thick and gigantic particles of hydrogen vapours.

The hydrogen clouds were “gravitationally unstable and matter coalesced to smaller denser clump, which then collapsed and formed stars” (Stamatellos, Hubber & Whitworth 2007, p.31). The formation of giant stars is illustrated below.

Source: (Stamatellos, Hubber & Whitworth 2007, p.30)

The nebular hypothesis also holds that the process of star formation is an intricate one. It produces hefty amounts of proto-planetary disks of gasses around a forming star. In the due process, this may truncate into the formation of planets.

Consequently, the procedure of star creation results to the innate configuration of terrestrial system. In this context, Fogg and Nelson (2007) claim that the hypothesis approximates, “…a sun-like star usually takes 100 million years to form” (p.1198). The proto-planetary disks are initially hot.

However, during the T Tauri star formation stage, it cools down upon attracting more dust grains that are composed of ice and rocks. This makes the first stage of formation of the planetary system. The second stage is marked by the coagulation of planentesimals to become kilometer-sized embryos right from centimeter-sized ones.

However, “ if the disk is massive enough, the runaway accretions begin, resulting in the rapid-100,000 to 300,000 years- formation of moon-to mars-sized planetary embryos”(Sean, Quinn, T & Lunine 2007, p.70).

Within the vicinities of stars, the developing embryos of planets undergo massive merging processes leading to the formation for terrestrial planets.

This is the last stage, which takes approximately 100 million years. The most complex development is that of the creation of colossal planets like Jupiter.

Giant planets

Formation of Giant planets is thought to take place under conditions that are below snowlines. In such situations, the emanating planets embryos are principally comprised of ices. Consequently, such planets are “several times massive than the inner part of the proto-planetary disks” (Fogg & Nelson 2007, p.1196).

The nebular hypothesis further postulates that the components that are formed after the formation of the ice embryo are necessary. This remains unclear even though growth may take place to surpass 5 to 10 times the size of the earth.

This threshold value is critical in the initiation of the process of accretion of gases (hydrogen-helium) from the surface of the disks. According to this theory, the course of gathering gases at the center of the springing planet is essentially slow.

However, “when the planet becomes 30 or more times greater than the earth, the process accelerates and extends into the runaway” (Montmerle et al 2006, p.41). The process of accretion does not proceed for eternity. It stops upon exhaustion of gasses. Consequently, planets acquire their defined masses since no further increase in masses occurs.

Planets already created may relocate themselves thus causing a failure of cores leading to the formation of planet-like Neptune and Uranus (Boss 2003, p.578). Cores leading to the formation of these two planets “were formed too late when the disk had almost disappeared” (Megeath et al 2005, p.113).

The nebular theory also holds that other components of the solar system were formed in similar manner in which the earth, the stars, and or giant planets such as Neptune, Saturn, and others were formed.

Asteroids

Just as Neptune was formed from failed cores, nebular theory claims that asteroids coupled with other planetesimals formed from failed formation of planets. Failed planets are essentially the objects that were formed from solar nebular (Bottke, et al. 2005, p.65).

However, they hardly ended up being large enough to compose a planet. From this explanation of the formation of asteroids, it is apparent that the initiation stages for formation of an element of the solar system may lead to the formation of another element under certain conditions such as the failure of a process to proceed to completion.

Conclusion

Many theories have been put forward to explain the formation of the solar system. One of such theories is the nebular theory of the formation of the solar system. The theory argues that the solar system was formed, and continues to evolve, through the coalescence of dust and ice among other particles in space.

The theory dates back to 1743 when Emanuel Swedenborg first put it forward. Although it later faced disfavours, the modern evidence based on studies of the formation of new stars has made its reaccepted. However, this does not mean that the theory has cleared up all its criticisms.

For instance, a prominent drawback of the theory rests on its inability to provide explanations of the manner in which materials that are accreted by proto-stars lose their angular momentum. Consequently, it becomes hard to explain why some stars possess planets while others do not have belts made of dust.

Amid these and other challenges of the nebular hypothesis, the paper has argued that the theory can explain the formation of some features of the solar system such as the stars, asteroids, and planets among others.

References

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Bottke, W, Durda, D, & Nesvorny, D 2005, ‘Linking the collisional history of the main asteroid belt to its dynamical excitation and depletion’, Icarus, vol. 179 no. 1, pp. 63–94.

Fogg, J & Nelson, P 2007, ‘On the formation of terrestrial planets in hot-Jupiter systems,’ Astronomy & Astrophysics, vol. 461 no.3, pp. 1195-1199.

Font, S, McCarthy, G, Doug, J, & Ballantyne, D 2004, ‘Photoevaporation of circumstellar disks around young stars,’ The Astrophysical Journal, vol. 607 no.2, pp. 890–903.

Gomes, R, Levison, F, Tsiganis, K & Morbidelli, A 2005, ‘Origin of the cataclysmic late heavy bombardment period of the terrestrial,’ Nature, vol. 435, no. 7041, pp. 466–469.

Klahr, H & Bodenheimer, P 2003, ‘Turbulence in accretion disks: vorticity generation and angular momentum transport via the global baroclinic instability,’ The Astrophysical Journal, vol. 582 no.2, pp. 869–892.

Kokubo, E & Ida, S 2002, ‘Formation of protoplanet systems and diversity of planetary systems,’ The Astrophysical Journal, vol.581 no.1, pp 666–680.

Megeath, T et al. 2005, ‘Spitzer/IRAC photometry of the ρ Chameleontis association,’ The Astrophysical Journal, vol. 634 no. 1, pp. 113-116.

Mohanty, S, Ray, J, & Basri, G 2005, ‘The T Tauri Phase down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs,’ The Astrophysical Journal, vol. 626 no. 1, pp. 498–522.

Montmerle, T et al. 2006, ‘Solar System Formation and Early Evolution: the First 100 Million Years’, Earth, Moon, and Planets, vol. 98 no. 4, pp. 39–95.

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Sean, R, Quinn, T, & Lunine, J 2007, ‘High-resolution simulations of the final assembly of Earth-like planets 2: water delivery and planetary habitability,’ Astrobiology, vol. 7 no. 1, pp. 66–84.

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Introduction

Nebular model, an explanation about the origin of the solar system was first proposed by Laplace in 1796. He suggested that the matter from which the solar system formed was at one time a nebula or a slowly rotating cloud of hot gas and dust. The dust and gas cooled and the cloud began to shrink. As the cloud became smaller, it began to spin more rapidly, and somehow became flattened. The rotation could have resulted from a combination of centrifugal forces while gravitational force caused the fragments of gaseous matter to be left behind. The rings fused into planets and moons while the larger part of the cloud formed the sun.

The nebular model is the most widely accepted hypothesis in cosmology, but has several flaws. First concerns about the speed of the rotating sun. The model predicts the speed of the rotating sun to be 50 times fast that its actual speed. Secondly, there are doubts that the rings hypothesized to form the planets would ever condense. However, this model seems to explain most of the phenomena observed in our solar system. These have been considered to be the evidence of the theory for a very long time. This has been supported by scans of the universe which indicate the process to be taking place elsewhere. In response to this, the paper is aimed at explaining the nebular model of the solar system in details and the features of the solar system that the model can explain. Despite the many theories about the formation of the solar system, the nebular model seems to be the most inclusive and which is associated with observable evidence.

Pre-solar nebular

The nebular model maintains that our solar system began to form when a fragment of a giant cloud of dust and gas began to collapse due to the gravitational forces exceeding the forces related to gas pressure that expanded it (Montmerle, et al, 2006. p.47). This collapse was triggered by a range of perturbations such as density waves in rotating galaxies and a supernova blast wave. Montmerle and others (2006) assert that the cloud had the size of about 20 pc while the collapsing fragment was about 1pascecs across (p.47). The fragments continued to collapse resulting to the formation of dense cores, about 0.01 to 0.1 pc in size11. The pre-solar nebular (one of the collapsing fragments) was to form our solar system. The mass of this fragment which was to form the sun was just larger that the mass of the sun. This part contained elements like hydrogen, helium as well as lithium while the other included heavier elements formed earlier.

Stable daughter nuclei of transitory isotopes like iron-60 which form only in exploding transitory stars have been revealed from studies of earliest meteorites. Therefore, a supernova must have occurred in a region near the sun. it is likely that the hypothesized formation of the sun was initiated by the supernova shock waves. The nebular became denser and caused the fragmentation. And since only enormous, transitory stars produce supernova, this formation must have taken place in the region where massive stars are formed, probably similar to Orion Nebular (Hester, Desch, Healy & Leshin, 2004. p.1117). Revelations from Kuiper belt and the strange materials it contains suggest that the formation of the sun occurred within a cluster of stars. The width of the cluster was between 6.5 and 19.5 light years and a mass of about 3,000 suns (Simon & Zwart, 2009. p.13).

In the Nebular model, the collapsing cloud begins to spin faster and faster because of the angular momentum being conserved. The condensation of the matter in the cloud was characterized by the bombardments of the molecules with escalating frequency, and their kinetic energy changing into heat energy. The core of the nebular, where the mass was concentrated, acquired much heat than the surrounding regions. For many years, the competing forces associated with gas pressure, gravity, rotation, and magnetic fields caused the contracting cloud to flatten into a spinning pancake shape (protoplanetary disc) and formed a hot, dense protostar or a star prior to hydrogen fusion at the core (Greaves, 2005. p.68).

During this stage in the formation of solar system, the sun is suggested to have been developed into a T Tauri star. In the presence of T Tauri star, it means that there are protoplanetary plates having smaller masses than the star itself. These discs may extend to several hundred light years and are somewhat cool, with the highest temperature being a thousand kelvins only (Küker, Henning & Rüdiger, 2003. p.397).

The Hubble Space Telescope observed potoplanetary discs that are 1,000 AU wide in regions where stars are formed like the Orion Nebular. With time, the temperature and pressure of the center of the sun went to an extent that the hydrogen gas contained started to fuse and created a source of energy within the disc that counteracted the gravitational contraction leading to a hydrostatic balance. At this juncture, the sun entered into the principal phase of its evolution, often referred to as the main sequence. Stars in this phase obtain energy from hydrogen fusion in their centers. Since the formation halted, the sun has existed as a main sequence.

Planetesimals

According to nebular model, the planets in our solar system formed from the same nebula as the sun, the sola nebula. The cloud fragments left from the formation of the sun were responsible for the planets formation (Boss, & Durisen, 2005. p.137). The common and accepted method by which this formation took place is referred to as accretion. In this method, the planets started out as dust particles orbiting around the inner protostar. These particles collected into bigger objects through fusion and later collided to form planetesimals. Through further collisions, these bodies ultimately increased in size at a rate of several centimeters annually for several million years that followed.

The solar nebular formed from very hot gases and dust and the heat could not allow volatile molecules to condense. Therefore, only silicates and metals (heavier elements) were the only constituents in the formation of terrestrial planets. These rocky planets became the so called terrestrial and include: Mercury the closest to sun; Venus the second nearest, Earth the third nearest and finery Mars the farthest of the rocky planets. Compounds with high melting points are very scarce in the universe and so the rocky planets grew to relatively small sizes. The terrestrial planetesimals grew to a small fraction of the Earth masses and stopped accumulating matter approximately 100,000 years after the sun was formed. Through collision and fusions of the terrestrial embryos that followed, the rocky planets are believed to have grown into their present sizes (Lin, 2008. p.58).

During the formation of the rocky planets, these planets remained engrossed in a gas and dust cloud disc. And because the gas had its own pressure plus the gravitational pressure, it orbited slower than the forming planets. The difference in pressure resulted in a drag which changed the angular momentum causing the planets to eventually move to new positions. The temperature differences in the disc controlled the rate by which the planets moved, yet the overall trend was for the planets nearest to the core to move inward as the nebular dissipated, leaving them in their present orbits.

Jovian planets essentially formed further away from the sun. This is past the snow line which is the area between Jupiter and Mars. In this region, the temperatures were lower and volatile elements could condense. These materials constituted the larger part of the Jovian planets. These compounds are more abundant in the universe than silicates and metals that formed the rocky planets. As the planet increased in size, they were able to consume the lighter gases that were most abundant in the solar nebular. Formation of the planets past the snow line collected to several times the earth masses in a period of about three million years. At present the Jovian planets comprise almost 99 percent of the total mass rotating around the sun.

Furthermore, it is believed that the existence of Jupiter near the snow line is not an accident. As the falling ice approached the snow boundary, it encountered a change in temperature and evaporated causing the surrounding area to accumulate a lot of water. This resulted in a reduction of the pressure and dust particles could spiral faster and thus stopped moving towards the sun. Effectively, the snow line formed a barrier that made the matter to accumulate fast at a short distance from the sun. The excess matter combined into a large body of several Earth masses that grew swiftly by acquiring hydrogen from the adjacent disc to the largest planet in the solar system. The lower masses for Saturn resulted from its later formation when most of the gas to consume had been swallowed by Jupiter.

All the T Tauri stars including the sun are characterized by strong stellar wind. Other stable stars may have weaker winds. Neptune and Uranus must have formed after Saturn and Jupiter, when the stellar winds had cleared much of the matter within the disc. Therefore, the planets acquired very small amounts of hydrogen and helium, probably one Earth mass each. In effect, the two planets are usually called the “failed cores”. Though, the formation assumptions of these planets bring a problem relating to the time taken to form them.

The actual distance of the planet from the sun suggests that the planets formation or the accretion could have taken a much longer period of time. This means that the formation of the planets took place a closer distance from the sun…probably near or between Saturn and Jupiter…and they later migrated to their present positions (Levison et al., 2007. p.258). Planet migration was on both directions during their formation, either to the warmer region or the cold regions. The growth of the planetisimals could have halted after many years when the strong stellar winds forced the material out of the solar nebular into interstellar region.

Formation of the moons

Moons have been known to revolve around many planets as well as other bodies in the Solar system. Three mechanisms could have been responsible for the formation of the moons and include: from a solar disc through co-formation, from bombarding fragments and confinement of the passing objects.

Saturn and Jupiter have several large moons including Europa, Io, Titan, and Ganymede, which might have formed from discs surrounding each planet in a similar way the giant planets originated from the discs surrounding the sun (Takato, et al., 2004. p.2224). This formation is indicated by the nearness of the moons to the planets and their relatively larger sizes. The indicated attributes cannot be attained through capture neither can the moons form from bombardment fragments due to their gaseous nature. Moons further away from the giant planets tend to have smaller sizes and have peculiar orbits with random inclinations. Only captured bodies could be having such characteristics. Unfortunately, such moons have been reported to be revolving in the opposite direction. Evidence on the capturing of passing objects is based on Triton which is a moon of Neptune which has many irregularities. This moon could probably have been captured with Kuiper belt.

The formation of the moons within the terrestrial planets could probably have been a consequence of collision or capture. Phobos as well as Deimos is believed to be captured asteroids outside the snow line. Stevenson (1987) suggested that the Earth’s moon might have formed from a particular, slanting collision (p.271). The object that caused the impact had a mass similar to that of Mars, while the collision possibly took place as the end of giants bombardment period approached. The bombardment released some of the fragments into the orbit, which then united to form the moon (Canup & Asphaug, 2001. p.710). Perhaps, the collision was the last in the sequence of fusions that formed the primary. The earth-Sun Lagrangian points are also believed to be some of the areas where the moons could have been formed. Charon, a moon in Pluto is believed to have formed from a large collision.

Features explained by nebular model

The nebular model explains many features of the sola system including:

• Density difference between Jovial and terrestrial planets
• Terrestrial planets have fewer and smaller moons than Jovian planets
• Most of the planets carry a disc shape
• All the planets revolve in one direction

The terrestrial planets have approximately similar densities as none accreted much of the low-density material, which still existed in vapour form in the region near the core of the solar system. Moving towards Mars and Asteroids, volatile condensates such as water are more available leading to lower densities. However, the bodies could grow big enough to allow for the gravitational swallowing of gases. Saturn and Jupiter grew large enough to accrete gasses which lowered their densities. The increasing density of the outermost planets is due to the low-density methane condensates which makes the planets to have higher levels of heavy materials which increase the density.

The nebular model explains the formation of moons to have occurred as a result of co-formation, impact fragments, and capture of passing objects. Only co-formation was possible in the region beyond frost line and resulted in moon almost the size of terrestrial planets. The circum-planetary disc as a result of solar nebular fragmentations resulted in the formation of many fragments that fused to form the planets and moons. However, the moons in the terrestrial planets formed as a result of bombardments and capture of the passing objects.

The collisions were not very frequent and could have occurred outside the terrestrial region sending the fragments into the interstellar region. In addition, the passing objects could only be captured within the Kuiper belt region in order to form a moon. Unfortunately, many objects passed outside this region and thus only a few could be captured.

Due to the competing forces from gas pressure, gravitational force, and angular momentum, the constricting nebular starts to flatten resulting into a spinning flattened object with a swelling at the core. The decreasing angular momentum support close to the poles indicates that the material will easily fall close to the top, and not at the equator. Therefore, there results a swell which finally leads to the disk shape. The disc should not necessarily be flat, but is typically thicker on the outside than inside.

The entire solar system including the sun and the planets were formed from the solar nebular in which an angular motion was involved. In turn, the resulting fragments also spiraled in the same direction but with varying velocities due to their accumulating materials. As the disc materials reduced and the stellar winds brew them into the interstellar region, the revolving bodies could not change the aspects that defined their flow and rotated on a specific orbit at a specified speed. However, the nebular model does not explain satisfactorily about the moons that rotate in the opposite direction, yet it claims to have been formed together with the planets. The only explanation could be that the moons formed from either collision outside the solar system or capture of a passing object to assume their present direction. There is also a possibility that the moons collided with other bodies and thus changing their direction of rotation.

Conclusion

The nebular model of the solar system is a comprehensive theory that explains the origin of the solar system basing on the existence of a cloud of gases and dust. The cloud contracted to form a disc-shaped nebular. The nebular then contracted to form small planetisimals. The planetisimals fused to form the planets. The moons could have formed from bombardments or capture of passing objects, but most of the larger moons for the jovial planets formed just like the planets. The nebular theory can explain why the planets revolve in the same direction or why most planets are disc shaped. It can also explain the difference in densities between jovial planets and terrestrial planets and why the rocky planets have fewer moons that the giant planets.

References

Boss, A. P. & Durisen, R. H. 2005. Chondrule-forming shock fronts in the solar nebula: a possible unified scenario for planet and chondrite formation. The Astrophysical Journal, 621(2), pp.137–140. Web.

Canup, R. M. & Asphaug, E. 2001. Origin of the Moon in a giant impact near the end of the Earth’s formation. Nature, 412 (6848), pp.708–12. Web.

Greaves, J. S. 2005. Disks around stars and the growth of planetary systems. Science, 307 (5706), pp.68. Web.

Hester, J. J., Desch, S. J., Healy, K. R. & Leshin, L. A. 2004. The cradle of the Solar System. Science, 304 (5674), pp.1116-1117. Web.

Küker, M., Henning, T. & Rüdiger, G. 2003. Magnetic star-disk coupling in classical t Tauri systems. Astrophysical Journal, 589 (1), pp.397. Web.

Levison, H. F. et al 2007. Origin of the structure of the Kuiper belt during a dynamical instability in the orbits of Uranus and Neptune. Icarus, 196 (1), pp.258. Web.

Lin, D. N. C. 2008. The genesis of planets. Scientific American, 298 (5), pp.50–59. Web.

Montmerle, T. et al. 2006. Solar system formation and early evolution: the first 100 million years. Earth, Moon, and Planets, 98 (1-4), pp.39 –95. Web.

Simon F. & Zwart, P. 2009. The Lost siblings of the Sun. Astrophysical Journal, 696 (13/16), p.13. Web.

Stevenson, D. J. 1987. Origin of the moon–The collision hypothesis. Annual Review of Earth and Planetary Sciences, 15 (1), pp.271. Web.

Takato, N. et al. 2004. Detection of a deep 3- m absorption feature in the spectrum of Amalthea (JV). Science, 306 (5705), pp.2224–7. Web.

NASA established a discovery mission named Genesis in 2001 that targeted the sun. Astronomy experts within NASA launched it in August 8, 2001. However, the mission is still ongoing since samples are under study. This spacecraft revolved around the sun and earth for four years collecting particles of solar wind.

The spacecraft entered the earth space in September 2004 above the Utah desert. Unfortunately, as it sped down towards the earth surface, its parachutes failed. Consequently, it crashed into the earth surface damaging some of its components. However, this crash did not damage the samples it was carrying. Thus, the scientists extracted them from the debris and transported them to a laboratory for analysis (Russell 1).

Purpose

The mission had various objectives, the first being the collection of solar wind samples and bring them to earth for analysis. This mission required a lot of expertise because there were specific areas where genesis was to collect these specimens. An additional objective of the mission was to increase the knowledge of the sun’s composition. Many scientists have planned for this mission for a very long time.

However, most of them have not accomplished it because of the nature of the sun. It is evident that they could not construct an appropriate instrument that could reach the sun without damaging along the way. An addition purpose of the mission was to find out the procedures that led up to the derivation of the solar system (Russell 2).

Instruments

The instruments used in the discovery mission include Genesis, which was the spacecraft. Additional instruments were silicon, aluminum, and gold foil collectors that purified the samples it collected in the sun. The mission was equipped with communication devices that conveyed the information collected in the sun. The most important instruments in this mission were the cameras that provided high dimension images and the sound detectors that conveyed any other movements in the sun a part from that of Genesis (Angelo, 262).

On its return journey, the capsule was fitted with parachutes means to open immediately it entered the earth surface. This was to provide it with a soft landing. Additionally, there were standby helicopters with the obligation of capturing the return capsule mid air. This strategy was to prevent it from crushing and splitting its contents (Angelo, 262).

Discoveries

The first discovery of the mission was the fact that the solar wind contained 350 wafers. In addition, the wafers contained various components like silicone and germanium. This was an important discovery in the mission as these components could help in further discoveries.

Thus, many scientists referred to it as an imperative initial discovery. Most importantly, this discovery gave assurance that the mission was in the right track. An additional discovery of this mission was that the sun consists of burning gases. This discovery arose from the scrutiny of Genesis’s temperature whenever it approached the sun to collect samples (Flores 70).

Importance of the discoveries

These discoveries were imperative because they answered the objectives of the mission. It is noteworthy that the presence of wafers and the composition of different gases will help the scientists to compute the isotopic fraction of oxygen and nitrogen in the sun. As a result, it will help in accomplishing the objectives concerning the sun’s composition.

An additional objective that will be addressed with this discovery is the increase of knowledge on the sun’s composition. Furthermore, the discoveries will aid in determining the processes involved in the solar system foundation (Flores 70).

Works Cited

Angelo, Joseph. Encyclopedia of space and astronomy. New York, NY: Infobase Publishing, 2006. Print.

Flores, Julián. A second genesis: stepping-stones towards the intelligibility of nature. World Scientific, 2009. Print.

Russell, Charles. The Genesis Mission. Massachusetts, MA: Springer Publishers. 2003. Print.

Our Solar System

Just as the name implies, the Solar System is a multifaceted system that encompasses an array of celestial bodies orbiting around the sun. A visit into the Adler Planetarium museum showcases these bodies displayed in a state-of-the-art facility. A theatre show ushers viewers with the rubric ‘Welcome to the Universe,’ commencing with a view of a blackened night sky thanks to a range of military-grade projectors.

It is of note that the show features a live presenter who guides the viewers on how to locate the fundamental celestial landmarks. A walk into the Solar System room gives one a first-hand experience of how it feels like to be in space. A view of the eight planets together with their specific features agrees with the theoretical explanation. For instance, the planet Saturn is displayed as the second largest and is surrounded by rings. An array of telescopes in the outer space viewing the Solar System shows how the pictures of these bodies are taken. Moreover, the System is donned with meteors and asteroids.

A reflection of a theoretical explanation of the Solar System reveals a true picture of the same, as displayed in the exhibition. It shows that the terrestrial planets, including Mercury, Venus, Earth and Mars, are the smaller planets. On the contrary, the outer four planets are large and they are surrounded by planetary rings, a composite of dust and minute objects. Jupiter is the largest of all the planets followed by Saturn. The exhibition displays the planet Saturn as having numerous and beautiful rings just like it is being depicted in the literature. It is noteworthy that these planets are displayed so that they lie on a flat plane (an ecliptic plane) just like it has been explained in the literature. The Sun is the largest body and lies at the centre of the Solar System (Johnson 1).

I chose the Solar System since I wanted to know if the exhibit captures all the important features that are mentioned in the literature.

Shoot for the Moon

A ‘Shoot for the Moon’ is a revelation of the first maiden journey to space by the Americans in the 1960s. Featured in the exhibition is the Gemini 12 spacecraft, exhibited with an all-time state-of-the-art technology. This was the last type of this series, launched on November 11, 1966, from Cape Canaveral. The visitors of the museum are invited to a Lunar Danger Training Lab to experience at first hand what it feels like to be on the Moon.

One experiences a ‘Lunar Leap’ and eventual ‘Touch Down’ on the moon. Alex, a robot, exhibits a series of tests performed on astronauts before they are deemed fit for survival on the surface of the Moon. It is of note that the exhibition is surrounded by artifacts that include “an Apollo 8 in-flight suit, Apollo 13 helmet and gloves, Lovell’s visual acuity test card from Gemini 7, and original flight plans and manuals flown on the Gemini 12 mission” (Pearlman 2).

Jim Lovell tells about the initial American journeys into space way back in the 1960s. Lovell shares his personal experiences and the series of setbacks that nearly hampered his ambition of space exploration. His perseverance allowed him to accomplish four spaceflight missions and ultimately travel to the Moon twice. The Adler Planetarium creates insights of these flights when Lovell and his shipmates explored space using Gemini 12. As such, the visitors get the feeling of how risky Lovell’s mission was in his quest to comprehend space science.

Vitally, my choice for this exhibit is owed to the fact that I have passion for space science and I dream of exploring the space in future.

Works Cited

Johnson, Steve. It’s a new, sparkling ‘Universe’ at Adler Planetarium. New York: Penguin, 2012. Print.

Pearlman, Robert. Adler Planetarium: Jim Lovell/Shoot for the Moon. Houston: TX, 1999. Print.

Dense planets are generally closer to the Sun than less dense planets. Dense materials (like iron) are generally closer to the center of a planet. These two observations are caused by very different processes. Explain what is different about the processes these two sets of processes (you will have to review the material on solar system formation as well as planetary interiors for this question).

The solar system planets formed when the nebula cloud particles combined to form a rotating disk that was billions of miles in diameter. The disk was formed because of the pulling action of the gravitational force between the nebula particles that acted towards the center of the disk. The disk particles were held together through electrostatic forces and rotated in the same direction as the rotation of the disk.

During the planetary formation process, the rotation of the disk caused the nebula particles to gain an angular momentum, which caused the speed of the particles to increase exponentially. The resulting disk was 0.003 light-years or 200 AU in diameter. During the planetary formation process, smaller bodies combined to form planetesimals in an accretion process. Planets were formed from planetesimals, which were formed from a combination of small particles, which increased in size to form the big planets in a few million years. The resulting planets, formed from planetesimals bodies, are referred to as protoplanets. Protoplanets were made of different types of radioactive materials, which influenced an increase in the temperature of the core of the planets.

High-temperature changes, melting rocks, and metals were the main causes of the creation of planets in the solar system. The process through which the planets were formed is known as differentiation. The differentiation process was caused by strong thermal effects on the radioactive materials at the core of the planets. The key elements that define the formation mechanisms of planets include rock and metals.

The formation of the Jovian planets was based on the physical and chemical processes that occurred on metals and rocky materials. Planetesimals planets were formed through the capture of the nebula materials, which consisted of large and low-density helium and hydrogen to make the dense solid cores of the Jovian planets. The main differences in the formation of the terrestrial and the Jovian planets included different chemical, physical, thermal, and gravitational differentiation processes. The outer planets were formed by ice particles that coalesced together.

A planet is found in a newly discovered solar system. It is a terrestrial planet that is 2.3 AU from its star, and its mass is 1.4 Earth masses. Would you expect it to be hot enough inside to be nearly molten (like Earth and Venus)? If so, what is the likely heat source? Explain your answer.

Yes, the planet could be as hot as the earth. The rationale for the answer is because the orbit of the discovered planet lies in the star’s habitable region. Besides, the mass of the planet which is 1.4 Earth masses does not allow the planet to be a gas giant. The mass and the distance between the planet and the parent star suggest that it has a rocky and metallic interior. That implies the planet is composed of rocky materials and the density of the temperature because of the density of the planet increases as we go deeper into the core of the planet.

The planet has sufficient heat that makes its center to be in a molten state because of the physical and chemical composition of the materials that make the core of the planet. The molten state is caused by disintegrating radioactive minerals.

Introduction

For almost two thousand years, the earth was believed to form the center of the solar system. However, in early 16^th century Nicolas Copernicus (an astronomer of the Polish origin) proposed a new perspective that, the earth was just a planet like any other and did not form the center of the solar system. He rather proposed that, the sun was the center of the solar system; he called his model the heliocentric system. His findings were written in a book called “On the Revolutions of the Heavenly Bodies” which was published after his death. This paper will give an in-depth analysis of the Copernican model, the Ptolemaic model, and then give a comparison between the two models.

Copernican model

Nicolas Copernicus designed his model of the solar system to achieve the greatest simplicity, within his physical and philosophical axiomatic framework. He sought to eliminate the unnecessary hypothesis of the Ancients concerning coincidences and correlations of planetary orbits by explaining these orbits in terms of his heliocentric approach. The Copernican model of the solar system consists of the central star sun surrounded by a family of planets in concentric circular orbits. Whether we accept Copernican model or the multi-star model of the solar system is a philosophical choice rather than a scientific decision. He came up with a new ordering of the solar system as illustrated in the figure below (Anon. “The Copernican Model”1)

From Copernican order of the solar system, we realize that, the Earth is placed in third position from the sun and that the moon goes around the earth it’s an orbit. The Earth goes around the sun once every day causing the stars to rotate around it in the other direction. Copernicus was able to prove that the sun and not the earth was the center of the solar system but held unto the assumption of circular motion. He found that, all the planets rotate around the sun in a circular motion but the time taken by each planet to complete one rotation differs. The planets which are closer to the sun take a shorter time as compared to the ones further from the sun. Each planet has an orbit called ellipses in which it rotates around the sun.

Despite all the research, Copernicus had carried out, he feared publishing his book because he did know how the other astronomers and the church would react. That’s why; his book was only published soon after his death. However, for over one hundred years, his book was widely accepted and used in the study of astronomy. Other astronomers emerged later to criticize his findings but were not able to completely do away with his work and it still forms the basis of the study of the astronomy. The most commonly used aspect of Copernicus’s model is that the solar system is heliocentric.

That is, the earth, moon, and planets relate around the sun in a uniform circular motion. This approach has one main advantage in that, if we are able to accept the fact that, the sun is stationary, then it is understandable that, the epicycles of the bigger planets to those of the inferior planets explains the orbit of the earth and thus all of the circles must be equal ((Anon. “The Copernican Model”4).

The Ptolemaic model

The Ptolemaic model was first developed in the second century. It was believed to be a complicated astronomical system that managed to estimate the position of each planet. Ptolemy observed that the motion of the planets would only be estimated through a mathematical devise and that the model that gives the right answer should be adopted since it is hard to know the truth. Ptolemy’ model assumed that, the earth and not the sun was the center of the solar system. Just like Copernicus, Ptolemy found that, planets move on an epicycle that moves in a much bigger circle referred to as a deferent. He assumed that the stars move around the spheres of the other planets.

This findings contrast with Copernicus finding in that, according to Copernicus,, the stars wove around the earth in an opposite motion to the earth’s movement around the sun. The following figure is an illustration of Ptolemy’s solar system (Anon. “Copernicus vs. Ptolemy” 2).

Comparison between Copernican model and Ptolemaic model

Copernicus model gives a deeper analysis of the solar systems and it is a better version as compared to the Ptolemy’s model. For instance, Copernicus rejected Ptolemy’s equant scheme and found out that, all the heavenly bodies move in uniform circles. Both motions move in the same direction uniformly although one is faster than the other. However, both Copernicus’ model and Ptolemy’s contains equal numbers of epicycles although Ptolemy’s epicycles are bigger than Copernicus.

Copernicus’s assertion that the sun was the center of the solar system was driven by two forces. The first force was the failure of Ptolemaic model to give precise prediction about the positions of the planets. This is because Ptolemaic relied on mathematical devices and the device which was believed to produce easy predictions was assumed to be true. The second reason was that, Copernicus was opposed to the fact that Ptolemy used big epicycles to elucidate the retrospective motions of the planets. According to him, the motion of the planets could be elucidated by assuming that the earth also moves around the sun (Betz 65).

The Ptolemaic explanation derives from a model that captures little of the physical reality of the solar system. Unlike the Ptolemaic model, Copernican model represents the solar system as a proper system. The Ptolemaic model held that everything (including the sun) revolves around the Earth, a special object in the model

Because Copernicus imposed uniform circular motion on his model, it could not accurately predict the motions of the planets as compared to Ptolemy’s model. However, Copernicus model was more elegant in idea than the Ptolemy’s model. Placing the sun at the center of the universe produced a symmetry among the motions of the planets that was pleasing to the eye and to the intellect. All of the planets moved in the same direction at speeds that were simply related to their distance from the sun. In the Ptolemaic model, the planets were not treated equally like in Copernican model, for instance the epicycles of Venus and Mercury remained at the center on the Earth-sun line (Anon. “Copernicus vs. Ptolemy” 2).

The model may have eventually won support for its elegance more than its accuracy. The Copernican model relies on uniform circular motion and consequently does not precisely describe the motions of the planets, but the Copernican hypothesis that the universe is heliocentric was correct. Despite his flawed model, Copernican’s hypothesis was a groundbreaking moment in the history of astronomy.

Although Copernicus proposed a revolutionary idea in making the planetary system heliocentric, he was a classical astronomer with tremendous respect for the old concept of uniform circular motion. In fact, Copernicus objected strongly to Ptolemy’s use of the equant. The gradual acceptance of the Copernicus hypothesis has been named the Copernican Revolution because it involved not just the adoption of a new idea but a total revolution in the way astronomers thought about the place of the Earth.

Copernicus believed that the most important feature of astronomy is that all heavenly motions must be uniform circular motion. Copernicus had a revolutionary idea that the solar system is centered on the sun, but his insistence upon uniform velocities and circular motion was wrong (Betz 65). Perhaps the present situation in cosmology is similar to the situation after Copernicus, but before Kepler and Newton.

Conclusion

We would expect that the Copernican system succeeds better at explaining the asymmetry of season across the hemispheres. As the Copernican model deals with the planets as a system, it has no difficulty in explaining the asymmetry of the seasons and the varying lengths of the days. In this sense, the Copernican model has a grater explanatory power: by adopting the mobility of the earth, it naturally explains retrograde motions, the seasons, and the relative distance of the planets from the sun. But the Copernican system is more unwidely than the Ptolemaic model, at least in this respect. Nevertheless, it retains a closer fit to the solar system than the Ptolemaic model

Works Cited

Anon. “Copernicus vs. Ptolemy: How do we know what is “right” in science.” Web.

Anon. “The Copernican Model: A sun-centered solar system.” Web.

Betz, Fredrick. Managing technological innovation: competitive advantage from change. New York: wiley- IEEE, 2003.

Introduction

In this report, my mystery solar system is composed of nine planets. From these, five form the inner solar system while four from the outer solar system. From the planets forming the inner solar system, I chose planets one and five to research and report on. On the other hand, for the outer solar system, I chose planets two and four to research and reported on.

Mystery solar system

The table below shows some important data about the aforementioned planets.

I believe planets 1 and 5 of the inner solar system fall within the terrestrial planets category since they are close to the sun (0.21 and 1.24 AU, respectively). Moreover, this is attested by the fact that they have no moons. If that is not enough, analysis of their sizes reveals that they are either smaller or almost equal to that of the planet earth (radius of 0.68 and 1.07 earth masses for planets 1 and 5, respectively). In order to arrive at the probable composition of these planets, their densities are what drove me to my conclusion. These planets are denser (5.5 and 4.53 g/cm3 for planets 1 and 5, respectively) vis-à-vis the other two outer solar planets. To this end, I concluded that they are made up of both rocky substances and heavy metals. Of note, the gases that are most likely to be dominant in these planets that are closer to the sun are the heavy gasses. As such, I concluded that these planets are encapsulated by carbon dioxide and nitrogen gases. Finally, with the composition of these two planets in mind, I concluded that they are heated internally courtesy of radioactivity (due to unstable heavy metals), accretion, and differentiation (when materials drop from a higher point).

On the other hand, I believe that planets 2 and 4 of the outer solar systems fall under jovian planets since they are gigantic (10.66 and 8.78 earth radii). Moreover, this is underscored by the fact that they are far away from the sun (9.84 and 53.21 AU from the sun). Data revealing their densities confirm that these planets are composed of lighter materials. The densities of planets 2 and 4 are 1.12 and 0.68 g/cm3, respectively. These are less than those of the other two planets forming the inner solar system. As such, I concluded that they have composed of both lighter gasses (He and H) and ices (H2O). The other evidence that confirms my conclusion is that these planets have relatively higher spin (15.2 and 8 hrs respectively) as compared to those of the inner solar system (8057.21 and 40.87 hrs, respectively). This makes them have relatively flattened poles. Having the composition of the planets in mind, I concluded that the internal heat of the planets emanates, chiefly, from the friction between gasses.

Planet 1 and 5 (Terrestrial planet)

When one is on the surface of planet one, he/she will weigh less since the gravitational pull is less than that on the earth. Basically, the force of gravity is proportional to the planetary mass. Since its mass is 0.305 earth masses, the gravitational pull is expected to reduce by this factor.

Assuming person 1 weighs x N on earth;

This person will weigh 0.305*x N Ξ 0.305x N.

Conversely, while on planet five, this person will weigh slightly heavier due to the fact that this person will experience a greater gravitational pull that is proportional to the planet’s mass (1.013 earth masses). Therefore, this person will weigh 1.013*x N Ξ 1.013x N.

The interior of terrestrial planets are likely to be hot enough to power geological activities now or in the past owing to the internal processes that continue to happen in situ. The energy derived through the processes of accretion, differentiation, and radioactivity are the ones responsible for the geological activities witnessed in these worlds. Radioactive decay is particularly an important process that initially generated a lot of interior heat on these worlds when they were still young. This process is significant in heat generation since these worlds are dominated by radioactive isotopes. Vitally, the heat generated through this process (E=mc2) is proportional to the planetary mass and the percentage composition of the heavy metals. As such, a lot of heat is anticipated from this process. Basically, a combination of these processes generates a lot of interior heat vital in driving geological activities.

The surface processes that are likely to happen on the surfaces of these worlds include impact cratering, volcanicity, tectonics, and erosions. Impact cratering happens when impactors, particularly comets, bombard the surfaces of terrestrial planets at terrific velocities (30,000 – 250,000 Km/hr), thereby creating craters on their surfaces. On the other hand, volcanicity happens when magma rises to shoot outside through a vent owing to an inbuilt pressure within the mantle. Plate tectonics happens when the plates forming the crust collide, shear, or separate. The forces behind these motions originate from the hot mantle that is always under convectional current. Finally, erosion happens when the rocky materials are shifted thanks to the agents of erosion.

The surface temperature of a planet is given by the formula below:

T= b/λ.

The constant of proportionality b is given by 2.9×10-3 m.K, and the variable λ is the wavelength of a planet’s irradiation.

Therefore, planet 1has a surface temperature T = 2.9 x 10-3/ (4.908 x 10-6) K Ξ 590.87 K

Planet 5 has a surface temperature T = 2.9 x 10-3/ (1.2293 x 10-5) K Ξ 235.91 K

No-greenhouse temperature is defined as the temperature of a planet in the absence of infrared absorbers that include carbon dioxide and water droplets, among others. For planets 1 and 5, this temperature is equivalent to 570 and 228 degrees Celsius, respectively. In comparison with the surface temperatures of the planets (591o C and 236o C for planets 1 and 5, respectively), it is evident that the greenhouse gasses are responsible for the increased temperature.

The fact that there are differences between the no-greenhouse temperatures and the surface temperatures of the planets, it goes without saying that these planets are encapsulated by atmospheres. Nonetheless, planet 5 is likely to have a thicker atmosphere than the planet one because it is massive and far a distance from the sun. As such, this planet has a greater gravitational pull and hence, less likely to suffer from atmosphere escape, a function of temperature.

The gases that are more likely to form the atmospheres of planets 1 and 5 are the heavy gases that can withstand the escape velocity. These atmospheres are dominated by carbon dioxide gas, oxygen, methane, sulfur dioxide, ammonia, nitrogen, and water. The composition of the atmosphere is such that as one moves away from the sun, the more a planetary atmosphere is dominated by lighter gases. To this end, planet 1 is likely to be dominated by CO2 gas, while planet five is probably dominated by both nitrogen and ammonia.

Conclusion

It is improbable that one would visit the planet one because of the high temperatures and the lack of oxygen. Planet 5 is hospitable because it is more like the planet earth. It has enough oxygen, and the temperatures are favorable.

Planets 2 and 4 (Jovian planets)

For planet 2, the composition of hydrogen and helium as a fraction of the whole mass is approximately equal to 13/100 or 0.13. Similarly, for planet 4, this fraction accounts for approximately 0.13.

Planet 2 is likely to have metallic hydrogen liquid because it is relatively massive with respect to planet 4. Metallic hydrogen liquid is a function of pressure. As such, planet 2 is less likely to possess this metallic hydrogen liquid.

The surface temperature T= b/λ.

Therefore, for planet 2: T = 2.9 x 10-3/ (3.8555*10^-5) K Ξ 75.2 K

For planet 4: T = 2.9 x 10-3/ (8.7588*10^-5) K Ξ 33.1 K

The clouds surrounding these two planets are made up of hydrogen, helium, and their compounds. These are very colorful.

The moons are less likely to have atmospheres for the reason that they lack sufficient gravitational pull owing to their relatively small sizes.

What processes drive plate tectonics?

The process that drives plate tectonics is believed to be thermal related. Basically, this thermal heat originates from the hot mantle embedded within a shell of plates. The hot mantle causes the motion of plates via a thermal convection mechanism. Ideally, whatever happens, is that the hot mantle rises in a fashion similar to conventional current. As it rises, it cools and then sinks. The process recurs once more.

This motion causes plates to move towards each other, move away, or slide past one another. When the plates move away from each other, they form divergent boundaries. Consequently, a rift in the crust forms. This would later be filled with the surrounding water. On the other hand, when plates move against each other, they form convergent boundaries that form mountains and volcanoes. Finally, when plates slide against each other, they form the transform-fault boundary. On many occasions, shallow earthquakes are experienced when these types of boundaries form.

The layers that make up the temperature structure of a planet’s atmosphere and the energy sources that heat them

A planetary atmosphere is made up of four main temperature layers. These layers include the thermosphere, mesosphere, stratosphere, and troposphere. The thermosphere encompasses two layers; the exosphere and some parts of the ionosphere (>80Km). Across this layer, the temperature increases with altitude. The mesosphere layer (17 Km

The greenhouse effect is a warming effect due to the presence of greenhouse gasses in the atmosphere that includes carbon dioxide (the most dominant gas). The greenhouse effect is not bad; however, recently, increased human activities have led to increased atmospheric carbon dioxide that has resulted in global warming. Basically, whatever happens, is that the heat emitted from the Earth’s crust (long wavelength) cannot penetrate through the ozone layer. This heat is, instead, irradiated back to the Earth, increasing its temperatures.

The four processes that can add gas to a planetary atmosphere and the five processes by which a planetary atmosphere can lose gas

The planetary atmosphere can be gained courtesy of gravitational field strength, which is basically strong in giant planets but less in smaller ones. This force attracts gasses to encapsulate a planet. Moreover, atmospheric gasses can be gained through volcanic outgassing due to volcanic activities. Also, the planetary atmosphere can be gained due to surface impacts, for instance, when a comet hits the surface of a planet to release gases. Finally, planetary gases can be gained through the processes of evaporation and sublimation that occur on open water sources.

The planetary atmosphere can be lost via chemical reactions. For instance, the planet Mars lost its oxygen due to an oxidation reaction with iron. Also, the planetary atmosphere can be lost thanks to solar winds that wipe away gases from planets with no magnetic fields. Moreover, the planetary atmosphere can be lost through thermal escape because of higher planetary temperatures. Finally, a planet’s atmosphere can be lost because of processes such as freezing and condensation, which emplace gases on the surfaces.

The water and carbon cycles in the Earth’s atmosphere and how feedback works within them

The water cycle is a series of processes that replenish the water that is utilized on the planet earth. This process is also called the hydrological cycle, and it involves a number of processes. First, the water from the surface of the Earth evaporates while the plants evapotranspire. The water droplets rise, cool, and then condense to form clouds. This will fall as precipitation on the surface of the Earth, flowing like rivers into oceans. This will evaporate, and as such, the process recurs.

Akin to the aforementioned cycle, the carbon cycle is another process vital in checking the atmospheric carbon in the atmosphere lest we suffer from carbon extremities. The carbon is made available to the atmosphere as CO2 gas by both plants and animals when they respire or when man burn fossil fuel. This is, in turn, eliminated from the atmosphere through the process of photosynthesis, where plants manufacture food. Secondary consumers (animals) feed on these foods, respire to provide energy to the body, and later die to form fossil fuel. This replenishes the lost carbon in the atmosphere. The process recurs to form a carbon cycle.

Calculation/Critical Thinking Problems

Going by the information provided about the inner solar systems, I believe planet five will have a strong greenhouse effect. This is because the planet is the most massive (1.013 earth masses), and as such, it has a strong gravitational pull than other planets. This will function to attract more gases than the other planets. Also, because it is far away from the sun (1.24 AU), it is unlikely that the atmosphere will be lost via thermal escape. The no-greenhouse temperatures attest that the planet is far much cooler than the others thus can retain the atmosphere. This is further emphasized by the wavelength of the light emitted (12293 nm); it is more than the others. This shows that it is relatively cooler than the others.

The surface temperature (T) of a planet is given by the equation below

T= b/λ. But b = 2.9E-3 m.K and λ is the wavelength of a plant’s irradiation.

Therefore, for planet 2, T = 2.9*10-3/ (6902*10-9) = 420 K.

Planet 3, T = 2.9*10-3/ (8956*10-9) = 324 K.

Planet 5, T = 2.9*10-3/ (12293*10-9) = 236 K.

Going by my expectations, planet five, which is further away from the sun, is the coolest. However, with an expected dense atmosphere, one would expect it to be the hottest. Nonetheless, a planet with a dense atmosphere is not necessarily the hottest. There are some other factors like the distance from the sun that determine the average planetary temperature.

My planet of choice for classification is planet 5 for the one that is less than ten earth masses and planet 3 for the one that is greater than ten earth masses. First, planet 5 is a terrestrial planet. This one has a relatively high density compared to the exoplanets. This high density is due to the fact that its core is mainly composed of heavy metals. Also, these types are typified by few moons or none. Its atmosphere is less dense and thus suffers from extreme diurnal temperatures. My planet 5, on the other hand, is classified as a gas giant (Jovian planet). This is typified by numerous moons, gaseous atmosphere, and liquid surfaces. Comparatively, it has a low density due to its composition.

Scientists believe that Europa has a subsurface ocean due to a number of pieces of evidence presented on the realm. First, Galileo spacecraft brought this to light when it sensed a rather induced magnetic field on this realm. Conductive substances were also detected within a depth of 30Kms. Also, the geographical makeup of the realm (fractured) strongly suggests that the plate is highly mobile.

Going by the evidence gathered, I believe that this information is scientific. In fact, the geographical evidence of the numerous fractures of the realm plus the chaotic terrain tells it all.

Introduction

The origin of the Sun and its orbiting planets has been a point of hypothesis and conjecture ever since man looked upon the stars and planets and wondered about their origins. For the ancient Greek and Roman civilization the celestial bodies they observed in the sky were thought of as Gods and Goddesses, looking down up the Earth from some form of godlike platform. Today, it is an established fact that the heavenly bodies we see in the night sky are composed of planets and stars, celestial bodies of rock, gas and varying forms of elements that were formed billions of years ago. Even though such objects have been observed for hundreds of years it is only within the last 200 that humanity has begun to understand their unique qualities. While there have been conjectures, varying hypothesis and age old established theories what must be understood is that as the science of astronomy evolves humanity begins to slowly adapt to new information, new discoveries and subsequent re-evaluations of what we knew of as fact. For example, early studies of astronomy adopted the geocentric model in that they believed that the sun, planets, moon and stars revolved around the Earth, not only that there was also the belief that the Earth was in fact flat (Copernicus, 2009: 83). It is based on this that when examining the established theories on the origins of the solar system one must do so with both an open yet skeptical mind, taking into account the given data and observations yet not clearly adhering to any one theory as being definitive proof.

Another interesting topic that should be taken note of is the origin of the Earth itself for just as there have been numerous theories as to the origin of the solar system there have been a plethora of theories which have attempted to determine the origin of the Earth itself. Our home planet is unique in that it is the only planet within our solar system that has sufficiently developed to be able to support life. While there have been varying accounts of how life came to be on Earth, with religion and science vying for attention, the fact remains that the uniqueness of our planet should not be underestimated and as such bodes a certain degree of curiosity as to the origins of the unique circumstances that enabled Earth to become what it is today. It is based on the various questions presented that this paper will explore the origins of the solar system and of Earth itself in order to attain a clear picture of where it came from and what its possible end could be.

The Nebular Hypothesis

Currently, one of the most widely accepted theories regarding the formation of the solar system is that of the nebular hypothesis which states that the solar system originated from a molecular cloud wherein through the introduction of an external force caused a gravitational collapse of the fragment resulting in the creation of A pre-solar nebula that would eventually become our solar system (Glassmeier, 2006: 1 – 5). While there has been no definitive evidence as to the exact origin of the external force that caused a section of the molecular cloud to collapse rather than dispersing it into space it is theorized that the energy from a nearby supernova produced sufficient enough force to cause the collapse and help trigger the necessary events needed to create the solar system. While few studies dispute the nebular hypothesis several do call into question the theory that a supernova caused the initial collapse. Studies such as those by Woolfson (2010) state that the energies from a supernova instead of causing a section of the molecular cloud to collapse would have actually dispersed a majority of the cloud into space thus preventing the formation of the solar system (Woolfson, 2000: 1 – 15). Furthermore, while the nebular hypothesis has been well established as a guiding concept in understanding the creation of celestial bodies little is known as to the precise origins of the molecular cloud that gave birth to the solar system itself. Several scientists such as Lognonne et al. (2007) state that origin of the Sun and its surrounding planets was a molecular cloud and go to great lengths explaining how it led to the creation of the solar system yet a lot of studies neglect to mention how the molecular cloud came to be in the first place (Lognonne et al., 2007: 1 -3)

Origin of the Molecular Cloud

While this paper has so far expounded on the nebular theory involving the Solar system’s origins as coming from a giant molecular cloud a rather interesting question comes to mind, “if the origin of the solar system is that of a giant molecular cloud where did the molecular cloud come from?”. Studies such as those by Sorrell (2008) explain that while our own sun is 4.5 billion years old the age of the universe itself has been estimated at roughly 13.75 billion years (estimate subject to change due to varying accounts as to the proper calculation) (Sorrell, 2008: 45 – 49). Furthermore it must be noted that our sun is not the oldest sun in the universe let alone in our galaxy and in fact can be considered in the prime of its “youth” as a main sequence star (Naylor, 2009: 432). It has been theorized by researchers such as Freire (2008) that a few billion years after the Big Bang, Super Massive stars, many times the temperature of our current sun and several times its size, were among the first stars to form within the universe (Freire, 2008: 459-460). These celestial bodies were able to grow to such great size due to less “competition” for available materials in order to coalesce into stars; it must be noted though that at this point in time planets were unable to form due to the lack of heavier elements in which a sufficient enough solid mass could coalesce into a planet (Dessart, 2010: 2113-2125).

Rather interestingly, it was actually due to the inherent instability of Super Massive stars that the universe became what it is today; this is due to the theory that as a direct result of their internal instability most of the original Super Massive stars became supernovas which actually caused the original molecular clouds in the universe to form (Dessart et al., 2010: 2120 – 2125). The original state of the universe was actually more “pure” in the sense that there was a distinct lack of heavier elements, as such the question of “where did the heavier elements come from?” comes to mind. This is actually resolved by looking at the activity of our own sun wherein through a process called stellar nucleosynthesis in which the nuclear reactions within the sun itself is able to help build the nuclei of elements that are heavier than hydrogen (Chiosi, 2010).

Runaway Star Hypothesis

In relation to the explanation of the origins of the molecular cloud as coming from the debris from Super Massive stars Courtland (2010) presents a new theory that details exactly how the molecular cloud that spawned the solar system came to be. In her study which involved the examination of various meteorites she discovered that sealed within the rock were calcium-aluminum rich incisions (Al-26) that could only have been formed by stars that were at least 10 times as massive as the sun (Courtland, 2010: 8). Due to the fact that Super Massive stars usually form within clusters with Al 26 usually decaying rapidly due to the intense heat within such clusters it is hypothesized by Courtland (2010) that a run away must have been tossed out of its orbit as a direct result of either an explosion of a nearby Super Massive star or due to combined gravitational push by its sibling stars within the cluster (Courtland, 2010: 8). Due to Super Massive stars having a relatively short life cycle when the star became a supernova the dispersed molecules and elements became the molecular cloud that we know of today as being the primary basis of the nebular hypothesis.

Formation of the Sun and Planets

Creation of the Sun

Since this paper has now established the various theories which attempt to explain the origins of the molecular cloud that brought about the creation of the solar it is now necessary to explain the current prevailing theory on how the planets and the creation of the sun came about. As mentioned earlier, in the section detailing the nebular theory, it was explained that as a direct result of a gravitational collapse of a section of the molecular cloud this precipitated the creation of the solar system (Boeyens, 2009: 493-499). A better explanation of this would be that as section of the nebula collapsed this produced a certain degree of angular momentum wherein the nebula actually began to spin faster as it collapsed in on itself. This spinning combined within the collapse produced a great deal of kinetic energy within the core of the molecular cloud until the result was a contraction of the center of the molecular cloud, which had now become a disc shaped object, into what is known as a proto-star, namely a star that has yet to have hydrogen fusion occur at its core (Boeyens, 2009: 493-499). Within 50 million years the internal temperature and pressure of the core itself was able to build to sufficient levels resulting in the start of hydrogen fusion marking the entry of the sun into its life as a main sequence star (Boeyens, 2009: 493-499)

Theory of Accretion

The theory of accretion is currently the most widely accepted theory proposing the creation of the planets, in it the theory indicates that the leftover material from the sun’s creation continued to spin around the sun slowly clumping together piece by piece until larger dust shaped particles were created (Ogihara et al., 2007: 522-530). Gradually these dust particles also began clumping together resulting in the creation of larger and larger objects until finally the entire solar system was composed of literally dozens of moon sized objects that crashed into each over a period of several million years (Ogihara et al., 2007: 522-530). It must be noted that the reason why such a process didn’t just create a system of bits and pieces of rock is due to the fact that these moon sized objects actually had viscous outer cores in the sense that their composition was similar to lava due to the high temperatures of the sun at the time and the process of accretion itself. As such when the objects collided what resulted was not a titanic clash that mutually shattered the objects but rather a process where both objects combined to form a larger structure or surfaces were “swapped” in the sense that certain parts of either proto-planet’s surface accreted to the colliding object (Ogihara et al., 2007: 522-530).

Creation of the Earth

Originally the Earth was a proto-planet no bigger than the moon yet over several million years the process of accretion was able to slowly build up the Earth to its present shape. It must be noted though that the early outer core of the planet was fluid in that due to the intense heat present at the time metals that had accumulated on the planet’s surface slowly submerged into the inner core creating the metallic core that is present today (Robin, 2008: 4061 -4075). Within 150 million years of the planet reaching its current mass the surface sufficiently cooled resulting in the creation of a primitive crust, yet unlike today the surface of the Earth is estimated by studies as being roughly 1600 degrees Celsius with numerous volcanoes dotting the landscape releasing gases into the atmosphere which formed the initial atmosphere of the planet which was kept in place by Earth’s inherent gravity (Robin, 2008: 4061 -4075).

Formation of the Oceans: Comet/Proto-planet Impact Theory

Most scientists agree that the presence of water on the Earth was the pivotal necessity necessary in order for life to start on the planet. When examining the process of Earth’s creation though there seems to be few indicators of water actually forming directly from the process of creation or within the Earth itself (Robin, 2008: 4061 -4075). One theory that attempts to explain this is the comet/proto-planet impact theory which states that proto-planets, planetoids and comets that were composed of ice were actually prevalent in the inner system during the later stages of the process of accretion. (Robin, 2008: 4061 -4075) As such as the Earth continued to orbit around the sun it supposedly impact millions of comets along with several icy proto-planets to create the water that can be seen in the oceans today. In fact, 4.4 billion years after the creation of the sun the Earth had actually sufficiently cooled enough to actually create clouds, rain, and the even oceans on the planets surface (Robin, 2008: 4061 -4075). This particular period marks the creation of the atmosphere that is present in the world today which is a combination of oxygen, carbon dioxide and other gases.

Conclusion

By the end of this paper it has become apparent that the process of creation of our solar system and even of our planet has been an accumulation of fortunate incidents that culminated in humanity evolving into its present state. When examining the theories explaining the creation of the molecular cloud, how Courtland (2010) presented the notion that the molecular cloud our present system came from originated from a rogue Super Massive star that coincidentally was shot out of its group by gravitational forces, that it was able to travel far enough to an area ideal enough for uninterrupted growth, that the creation of our planet was in the right place, at the right time with readily available water literally crashing into the planet in order to support life; a combination of all of these completely coincidental factors almost leads one to believe that the creation of humanity itself was no accident but on purpose. On the other hand there are quite literally billions upon billions of solar systems within the universe and it might actually be the case that the process that created the Earth is not so coincidental and that somewhere out there life similarly exists on thousands of planetary systems with the exact same composition as that of humanity yet far away enough that we cannot see the similarities at the present.

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