Origin of the Solar System

LESSON 2

Content Standard 

1. The learners demonstrate an understanding of the formation of the universe and the solar system. 
2. Learning Competencies 
3. The learners shall be able to describe the different hypotheses explaining the origin of the solar system (S11/12ES-Ia-e-2) and explain the current advancements/information on the solar system (S11/12ES-Ia-e-5) 

Specific Learning Outcomes 

At the end of this lesson, the learners will be able to: 

1. Identify the large scale and small scale properties of the Solar System; 
2. Discuss the different hypotheses explaining the origin of the solar system; and
3. Become familiar with the most recent advancements/information on the solar system.

Solar System

Overview

• The solar system is located in the Milky Way galaxya huge disc- and spiral-shaped aggregation of about at least 100 billion stars and other bodies;
• Its spiral arms rotate around a globular cluster or bulge of many, many stars, at the center of which lies a supermassive black hole;
• This galaxy is about 100 million light years across (1 light year = 9.4607 × 10^12 km);
• The solar system revolves around the galactic center once in about 240 million years;
• The Milky Way is part of the so-called Local Group of galaxies, which in turn is part of the Virgo super cluster of galaxies;
• Based on on the assumption that they are remnants of the materials from which they were formed, radioactive dating of meteorites, suggests that the Earth and solar system are 4.6 billion years old on the assumption that they are remnants of the materials from which they were formed.

  

Large Scale Features of the Solar System

1.       Much of the mass of the Solar System is  concentrated at the center (Sun)  while angular momentum is held by the outer planets.

2.       Orbits of the planets elliptical and are on  the same plane.

3.       All planets revolve around the sun. 

4.       The periods of revolution of the planets increase with increasing distance from the Sun; the innermost planet moves fastest, the outermost, the slowest;

5.       All planets are located at regular intervals from the Sun.

Small scale features of the Solar System

1.       Most planets rotate prograde

2.       Inner terrestrial planets are made of materials with high melting points such as silicates, iron , and nickel. They rotate slower, have thin or no atmosphere, higher densities, and lower contents of  volatiles - hydrogen, helium, and noble gases.

3.       The outer four planets - Jupiter, Saturn, Uranus and  Neptune are called "gas giants" because of the dominance of gases and their larger size.  They rotate faster, have thick atmosphere, lower densities, and fluid interiors rich in hydrogen, helium and ices (water, ammonia, methane).

Element Abundance on Earth, Meteorites, and Universe

A.      Except for hydrogen, helium, inert gases, and volatiles, the universe and Earth have similar abundance especially for rock and metal elements. 

B.      The sun and the large planets have enough gravity to retain hydrogen and helium. Rare inert gases are too light for the Earth’s gravity to retain, thus the low abundance. 

C.      Retention of volatile elements by the Earth is consistent with the idea that some materials that formed the Earth and the solar system were “cold” and solid; otherwise, the volatiles would have been lost. These suggest that the Earth and the solar system could be derived from materials with composition similar to that of the universe.

D.      The presence of heavy elements such as lead, silver, and uranium on Earth suggests that it was derived from remnants of a supernova and that the Sun is a second-generation star made by recycling materials.

Abundance of elements

Earth’s origins known mainly from its compositional differences with the entire Universe. Planet-making process modified original cosmic material.

Origin of the Solar System

Any acceptable scientific thought on the origin of the solar system has to be consistent with and supported by information about it (e.g.  large and small scale features, composition).  There will be a need to revise currently accepted ideas should data no longer support them.

Rival Theories

Many theories have been proposed since about four centuries ago. Each has weaknesses in explaining all characteristics of the solar system.

Nebular Hypothesis

In the 1700s Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace independently thought of a rotating gaseous cloud that cools and contracts in the middle to form the sun and the rest into a disc that become the planets. This nebular theory failed to account for the distribution of angular momentum in the solar system. 

 

Encounter Hypotheses:

A.      Buffon’s (1749) Sun-comet encounter that sent matter to form planet;

B.      James Jeans’ (1917) sun-star encounter that would have drawn from the sun matter that would condense to planets, 

C.      T.C. Chamberlain and F. R. Moulton’s (1904) planetesimal hypothesis involving a star much bigger than the Sun passing by the Sun and draws gaseous filaments from both out which planetisimals were formed;

D.      Ray Lyttleton’s(1940) sun’s companion star colliding with another to form a proto-planet that breaks up to form Jupiter and Saturn. 

E.       Otto Schmidt’s accretion theory proposed that the Sun passed through a dense interstellar cloud and emerged with a dusty, gaseous envelope that eventually became the planets. However, it cannot explain how the planets and satellites were formed. The time required to form the planets exceeds the age of the solar system.

F.       M.M. Woolfson’s capture theory is a variation of James Jeans’ near-collision hypothesis. In this scenario, the Sun drags from a near proto-star a filament of material which becomes the planets. Collisions between proto-planets close to the Sun produced the terrestrial planets; condensations in the filament produced the giant planets and their satellites. Different ages for the Sun and planets is predicted by this theory.

Sun - Star interaction

Nobel Prize winner Harold Urey’s compositional studies on meteorites in the 1950s and other scientists’ work on these objects led to the conclusion that meteorite constituents have changed very little since the solar system’s early history and can give clues about their formation. The currently accepted theory on the origin of the solar system relies much on information from meteorites.

  

Protoplanet Hypothesis - Current Hypothesis

A.      About 4.6 billion years ago, in the Orion arm of the Milky Way galaxy, a slowly-rotating gas and dust cloud dominated by hydrogen and helium starts to contract due to gravity 

B.      As most of the mass move to the center to eventually become a proto-Sun, the remaining materials form a disc that will eventually become the planets and momentum is transferred outwards. 

C.      Due to collisions, fragments of dust and solid matter begin sticking to each other to form larger and larger bodies from meter to kilometer in size. These proto-planets are accretions of frozen water, ammonia, methane, silicon, aluminum, iron, and other metals in rock and mineral grains enveloped in hydrogen and helium.

D.      High-speed collisions with large objects destroys much of the mantle of Mercury, puts Venus in retrograde rotation. 

E.       Collision of the Earth with large object produces the moon. This is supported by the composition of the moon  very similar to the Earth's Mantle

F.       When the proto-Sun is established as a star, its solar wind blasts hydrogen, helium, and volatiles from the inner planets to beyond Mars to form the gas giants leaving behind a system we know today.

 

 Recent advancement/information on the Solar System

·         Exploration of Mars

Since the 1960s, the Soviet Union and the U.S. have been sending unmanned probes to the planet Mars with the primary purpose of testing the planet's habitability.  The early efforts in the exploration of Mars involved flybys through which spectacular photographs of the Martian surface were taken.  The first successful landing and operation on the surface of Mars occurred in 1975 under the Viking program of NASA.  Recently, NASA, using high resolution imagery of the surface of Mars, presented evidence of seasonal flow liquid water (in the form of brine - salty water) on the surface of Mars. 

Rosetta's Comet

Rosetta is a space probe built by the European Space Agency and launched on 2 March 2004.  One of its mission is to rendezvous with and attempt to land a probe (Philae) on a comet in the Kuiper Belt.  One of the purpose of the mission is to better understand comets and the early solar systems. Philae landed successfully on comet (67P/Churyumov–Gerasimenko) on 12 November 2014.  Analysis of the water (ice) from the comet suggest that its isotopic composition is different from water from Earth

·         Pluto Flyby

On 14 July 2015,   NASA's New Horizon spacecraft provided mankind the first close-up view of the dwarf planet Pluto.  Images captured from the flyby revealed a complex terrain - ice mountains and vast crater free plains. The presence of crater free plains suggests recent (last 100 millions of years) of geologic activity.

Additional Learning Materials

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DOWNLOAD THE PDF VERSION HERE.

Reference: 

Teaching Guide for Senior High School EARTH AND LIFE SCIENCE. Published by the Commission on Higher Education, 2016