Module #2 - Solar System Origins


1. Watch the Video of the Day:  PBS: Origins of Our Solar System (13 minutes) and make point form notes in your digital video journal. Please make sure that you SHARE your VIDEO JOURNAL document with Mr. Durk. (click on link for template and exemplar). You may decide to watch the video at a later time, as you may want to start Parts 2 and 3 in class today.

2. Read the following information / Content below in Part 1: Background and Terminology. Follow all hyper-links (BLUE) to external websites for activities, demonstrations and videos (if applicable). Copy only KEY information (i.e. the highlighted terms) to your digital notebook (in google docs). You may will need to decide which content is important and make point form notes accordingly.

3. Complete Part 2: Assignment (see below) and post onto the Discussion Board (using UGDSB LMS). NOTE: Please use google docs and 

4. Complete Part 3: Group Assignment - only in partners (see below) and submit to Mr. Durk via UG Cloud Share (Module #2: BOTH OF YOUR NAMES) - it must be in your Module folder. Be sure to complete the presentation in Google Slideshows or Prezi or any other ONLINE presentation software. Be sure to delegate work as you will have to complete on your own time outside of class.

DUE DATE:  Before Module #3: Thursday February 18th

As you will observe throughout this course, systems are an integral part of studying Physical Geography. In fact, upon completion of this course, you will have encountered many systems. This activity will concentrate on such a system and its quest for balance. Before we begin to study planetary systems, it is important to understand the origins of an even greater system, the universe.

Please remember to record all definitions and content in your digital notebook (using google docs). Links to WIKIPEDIA articles can be found by clicking on highlighted words in RED. Hyperlinks to other external websites are highlighted in BLUE.

Part 1: Background Information and Terminology

Your Task: Read information, make point form notes in your notebook (either using google docs or pen and paper) and follow all hyper-links to related sites. Watch all videos that are listed below also (no need to make notes, but you can if you wish)

Origins of the Universe

How old is the universe? How was it created? How has it evolved over time? These are only a few questions about the origins of the universe that have baffled many scientists since the dawn of curiosity. No one knows the exact answers to these questions. It is likely that no one will ever be able to answer these questions accurately; however, with more innovative tools, astronomers are significantly bridging the gap of knowledge about the origins of the universe.

The study of the origin and evolution of the universe is often termed cosmology (in contrast with cosmogony, which refers to the study of the origin of the solar system). Astronomers have set for themselves three major tasks in the field of cosmology: to understand how galaxies evolved from the earliest times to the present; to refine and extend the scale of cosmic distances; and to test fundamental theories of the expanding universe.

The three main theories put forward to explain the origin and evolution of the universe are:

  • The Steady State Theory
  • The Pulsating Theory
  • The Big Bang Theory

1. Steady State Theory:

The steady state theory (also known as the Infinite Universe Theory or continuous creation) is developed in 1948 primarily by Hoyle, Gold and Bondi as an alternative to the Big Bang theory. Although the model had a large number of supporters among cosmologists in the 1950s and 1960s, the number of supporters decreased markedly in the late 1960s with the discovery of the cosmic microwave background radiation, and today only a very small number of supporters remain. The steady state theory asserts that although the universe is expanding, it nevertheless does not change its look over time. For this to work, new matter must be formed to keep the density equal over time. According to this theory, the number of galaxies in the observable universe is constant and new galaxies are continuously being created out of empty space, which fill up the gaps caused by those galaxies, which have crossed the boundary of the observable universe. As a result of it, the overall size of mass of the observable universe remains constant. Thus a steady state of the universe is not disturbed at all.

2. Pulsating Theory:

According to this theory, the universe is supposed to be expanding and contracting alternately i.e. pulsating. At present, the universe is expanding. According to pulsating theory, it is possible that at a certain time, the expansion of the universe may be stopped by the gravitational pull and then the universe may contract again. After it has been contracted to a certain size, explosion again occurs and the universe will start expanding. The alternate expansion and contraction of the universe give rise to a pulsating universe.

3. Big Bang Theory:

Acknowledgements: Image courtesy of NASA/JPL

The most widely accepted theory in the field of astronomy today is the Big Bang Theory, first proposed in the 1920s and 1930s. By observing physical properties of the universe, proponents of this theory speculate that time began about 12 to 15 billion years ago, when all of the matter within the universe exploded from a singularity, a dense point with an infinitely small volume. The Big Bang theory is based upon three main supporting observations.

The first of these observations is that the universe appears to be expanding. By observing light from distant galaxies, it was discovered in the 1920s that this light is shifted towards the red end of the spectrum, implying that galaxies are receding from the earth. The Big Bang theory states that this recession is not due to the movement of the galaxies through space, but instead is an expansion of space itself. Assuming that the universe is expanding as a whole and that it has been since the beginning of time, cosmologists extrapolate back in time to when the universe was a small point.

The second observation relates to the relative abundance of chemical elements within the universe. The Big Bang model predicts that the universe should be composed of approximately 75% hydrogen, 25% helium, and small amounts of heavier elements. Although these predictions depend on the initial conditions of the early universe, which are nearly impossible to know accurately, the observable universe is nonetheless composed of about three-quarters hydrogen and one-quarter helium, along with small amounts of heavier elements.

The third observation concerns cosmic radiation. In 1948, a Russian astronomer named George Gamow speculated that the initial fireball of the Big Bang explosion should have left behind a uniformly distributed radiation which would fill the universe and cool as the universe expanded, and be visible in every direction of the sky. The Cosmic Background Radiation (CBR), as this radiation is called, was first detected in 1965 in the form of radio waves, and has a uniform temperature of 2.7K. The discovery of this radiation swayed many astronomers in favour of the Big Bang theory.

Every theory involves assumptions, and the Big Bang is no exception; however, despite being proposed in the 1920s, the model has survived the scrutiny of 80 years of technological advancements and competing theories, contributing to its credibility.

Acknowledgements: Canadian Space Agency

From within this infinite system, the universe, emerge other systems such as galaxies which, in turn, host solar systems.

Please remember to record all definitions and content in your digital notebook. Links to external sites can be found in BLUE. Please follow each link to explore each of these links.

Formation of Galaxies

How galaxies formed after the Big Bang is a question still being studied by astronomers. Astronomers hypothesize that approximately a billion years after the Big Bang, there were clumps of matter scattered throughout the universe. Some of these clumps were dispersed by their internal motions, while others grew by attracting other nearby matter. These surviving clumps became the beginnings of the galaxies we see today. They first appeared about 14 billion years ago.

When a clump becomes massive enough, it starts to collapse under its own gravity. At this point, the clump becomes a protogalaxy. Astronomers hypothesize that protogalaxies consist of both dark matter and normal hydrogen gas. Due to collisions within the gas, the hydrogen loses energy and falls to the central region of the protogalaxy. Because of the collisions of the gas, protogalaxies should emit infrared light. The dark matter remains as a halo surrounding the protogalaxy.

A recreation of a the Milky Way galaxy 

Image Acknowledgements: Canadian Space Agency
URL: Canadian Space Agency

Astronomers think that the difference in appearance between elliptical and spiral galaxies is related to how quickly stars were made. Stars form when gas clouds in the protogalaxy collide. If the stars are formed over a long period of time, while some stars are forming, the remaining gas between the stars continues to collapse. Due to the overall motion of matter in the protogalaxy, this gas settles into a disk. Further variations in the density of the gas result in the establishment of "arms" in the disk. The result is a spiral galaxy. If, on the other hand, stars are made all at once, then the stars remain in the initial spherical distribution that the gas had in the protogalaxy. These form an elliptical galaxy.

Astronomers also think that collisions between galaxies play a role in establishing the different types of galaxies. When two galaxies come close to each other, they may merge, throw out matter and stars from one galaxy, and/or induce new star formation. Astronomers now think that many ellipticals result from the collision of galaxies. We now know that giant ellipticals found in the center of galaxy clusters are due to multiple galaxy collisions.

Acknowledgements: NASA

Follow this LINK to learn more about the different types of exist in our Universe.

Introduction to the Milky Way

All the stars we see in our night sky are contained within our own galaxy, the Milky Way. A galaxy is a gravitationally bound system containing billions of stars along with interstellar gases and dust.

Because we are located within the Milky Way Galaxy and have never been able to view it from the outside, it can be difficult to determine the exact appearance of our galaxy. However, by studying other galaxies and by observing of the material within our own galaxy, astronomers now recognize the Milky Way as a spiral galaxy, a flattened disk with a central galactic bulge and spiral arms curling out from the centre. The entire galaxy rotates about its centre, with our sun, located on one of the spiral arms, traveling at about 230 kilometres per second and completing one galactic orbit every 200 million years. Surrounding the flattened disk is the galactic halo, a faint and roughly spherical region of old stars and star clusters. From the earth, the Milky Way appears as a hazy, luminous band or cloud of light which stretches across the night sky. This band of light seen from a dark site is our view looking out through the galactic disk. It is a collection of millions of stars along with glowing gases which are so far away and condensed that they appear as a luminous haze instead of individual points of light.

Follow this LINK to visualize the Milky Way Galaxy and our place within it.

Our Home in the Milky Way

The Milky Way galaxy is an immense collection of material, such that the size is very difficult to imagine. Given that one light year is the distance light travels in one year, travelling at a speed of over one billion kilometres per hour, and that a light year equals nearly 10 trillion kilometres, it is no wonder many are baffled when told the circular disk of our galaxy is approximately 100,000 light years across. The sun is located about two thirds of the way out from the galactic centre, on one of the spiral arms.

Our solar system and the stars visible in our sky comprise an extremely small portion of our galaxy. Our galactic centre cannot be seen in optical light due to heavy obscuration from foreground stars and interstellar matter; we can only see about a tenth of the way toward the centre. In a dark rural sky less than 3000 stars are visible to the naked eye, but the Milky Way galaxy contains billions of stars. These stars often form in clusters, when a large interstellar cloud collapses and fragments into several smaller protostars. It is believed that many stars have planets in orbit around them, creating new solar systems. Although stars are very far away, making it impossible to visually see orbiting planets, astronomers have identified about a hundred such stars using other techniques. One method of detecting planetary systems is the measurement of slight perturbations or variations in the star’s apparent location, as it is influenced by the planet’s gravity. Astronomers are able to detect such variations with advanced modern telescopes, and as a result, are able to infer the existence of other solar systems in our galaxy. This technique requires the detection of extremely small variations in a star's position, and as a result is only useful for relatively nearby stars. The MOST project is a Canadian satellite which was launched in June of 2003 and is designed to measure slight variations in stars, undetectable from the earth. Recently, a new technique has led to the discovery of a planet orbiting a much more distant star. This technique involves measuring the brightness of a star, and looking for a slight periodic drop in intensity, which is speculated to be caused by an orbiting planet passing in front of the star and blocking a small portion of its light. None of the planets discovered thus far are considered to be Earth-like; their masses range from one-fifth up to ten times the mass of Jupiter, and they orbit their stars at distances of up to about 3 AUs.

Formation of a Star

Stars form in cold, dark clouds of gas and dust. The cloud must be relatively cold for stars to form because the particles must be moving slowly enough to allow gravity to overcome internal pressure and form clumps of matter. The interstellar cloud must also be truly immense, covering billions of kilometres, and must be reasonably dense with hydrogen and helium atoms for a star to form. It is thought that a shockwave from a nearby star will trigger a collapse of the cloud, after which the atoms slowly draw together due to the gravitational attraction between them. As the cloud shrinks, it breaks up into smaller fragments known as protostars. An initial interstellar cloud can produce hundreds of protostars. A protostar is a star in its embryonic stage, and although it glows due to the release of gravitational energy, it is not yet hot enough to produce nuclear reactions within its centre. As the protostar continues to collapse due to gravity, it will attract more atoms and continually increase in mass and density. The increased density and gravity will cause the core temperature to eventually rise to about ten million Kelvin, hot enough to convert hydrogen into helium (nuclear fusion). Millions of years after the interstellar cloud first began to collapse, a star is created.

Video: The Formation of a Star (only 40 seconds in length)

The Sun

The surface of the sun was originally thought to be perfect and uniform, but we now know the photosphere is marked by numerous irregularly shaped dark patches called sunspots. Sunspots are depressed areas on the sun that have a lower temperature than the surrounding surface. They are typically about the size of the earth, and are composed of a darker central region called the umbra, which is surrounded by a lighter coloured ring called the penumbra. They are temporary features and constantly alter the appearance of the photosphere. Sunspots are closely tied to the solar magnetic field and often occur in groups or in pairs of opposite polarity.

The rotation period of the sun would be very difficult to determine without the aid of sunspots. Because the sun is not solid, it experiences differential rotation, meaning that the surface rotates at different speeds depending on latitude, with the equatorial regions rotating faster than the polar regions. The number of visible sunspots varies year to year, and the frequency follows a regular 11-year cycle between times of maximum and minimum. During times of maximum, hundreds of sunspots are visible, whereas during a minimum, the photosphere can be devoid of any sunspots. Complex sunspot groups cause the eruption of solar flares, which produce a substantial release of solar particles into the solar wind. Because charged particles from the sun cause the aurora on Earth, the number of sunspots directly affects these displays. During a sunspot maximum like in 2001, we tend to see amazing auroral displays, and during minimums the aurora are essentially non-existent.
            Our Sun: "An Average Star"                         
                       Source: NASA

Formation of the Solar System

M16 - Star Forming Region

Although the origin of the solar system is still not fully understood, the basic concepts are known quite well. The nebular theory describes the slow collapse of a nebular cloud into a protostar as described in Module 2. While a star is forming in the centre of the collapsing cloud, the outer, cooler regions of the cloud swirl around the central protostar in a disk-like structure called the solar nebula.

An advanced theory, called the condensation theory, includes the nebular theory but also incorporates interstellar dust as an essential ingredient in the formation of the planets. This theory claims that the dust grains of the interstellar medium helped cool the nebular cloud by radiating heat away, and also acted as a foundation upon which atoms could attach. These properties of the interstellar dust grains aided in the collapse of the nebula and in the formation of planets. As these atoms continued to accumulate new material, they grew into larger clumps which gathered still more particles as they swept through the materials of the nebular cloud. Through the process of accretion, objects of a few hundred kilometres in diameter began to form. As these protoplanets grew in size, a snowball effect was apparent; the larger the protoplanet became, the more rapid its growth. It had a larger surface area on which to collect smaller clumps that soon became massive enough to produce their own gravitational fields and began to attract materials. In addition to the large objects getting larger, their large gravitational fields began to accelerate the smaller particles to high velocities, causing many high-speed collisions and, therefore, the fragmentation of these particles into even smaller pieces. These tiny pieces of material were influenced more readily by the large protoplanets, and as a result were swept up more rapidly. This resulted in the formation of a relatively organized solar system out of chaotic beginnings: nine protoplanets and a relatively small amount of interstellar material . The four largest protoplanets began an additional stage of development; they were large enough to generate a gravitational field strong enough to pull in the remaining gases of the solar nebula.

Another factor in the development of the four inner terrestrial planets and the outer gaseous planets was temperature. After the protoplanets had formed, the central regions of the solar nebula were collapsing and forming the sun, as described in Module 2. The young sun caused the temperature of the closer inner protoplanets to be higher than the outer protoplanets. As a result, the kinetic energy of the gaseous molecules was too high for them to coalesce, and they simply dissipated. At the outer planets, however, the molecules were cold, and were moving slowly enough for gravity to overcome their movement. Over the course of several million years, the planets grew into the planets we know today. The solar system was thought to have formed in this manner about four and a half billion years ago.

Asteroid IDA

In the grand scheme of the solar system, cometsasteroids and meteoroids are relatively unimportant objects, altogether totalling only about 10% the mass of Earth’s moon. Nonetheless, comets can still be very beautiful and intriguing objects, with bright heads and extended tails of glowing gases. The majority of comets are located in the Oort cloud, a distant cloud of slow moving comets extending out to a distance of several thousand AU’s. Most comets in our sky originate from this cloud, and have extremely long orbital periods. Although new comets are discovered each year, they are almost always long-period comets (short-period comets would most likely have been discovered in the past) and their passage over the Earth will not be seen again for generations.

 Asteroids and meteoroids are small pieces of rock left over as debris from the formation of the solar system. Asteroids are larger than meteoroids and are typically found between the orbits of Mars and Jupiter. Meteoroids, on the other hand, are significantly smaller and are randomly located throughout the solar system. Meteoroids traveling through Earth’s atmosphere are called meteors, shining as bright flashes of light also known as “shooting stars." The streak of light is caused by the release of energy as the grain-sized particle burns up due to the friction between it and the upper atmosphere.

                          Asteroid Ida


Meteor showers occur in regular intervals and are caused when the Earth travels through a region of space packed with small dust particles left by a passing comet. Witnessing a meteor shower can be an amazing sight, as hundreds of streaks of light can cross the sky in a single night. If a meteoroid is large enough or dense enough, it will survive its journey through the atmosphere and will reach the earth as a meteorite. A meteorite is a significant object for scientists studying the early solar system, as its relatively unchanged composition can give valuable clues to the formation of our solar system, which was formed out of a swirling solar nebula a few billion years ago.

Early Theories on the Solar System

The Planets of Our Solar System and their relative sizes
Source: NASA

Watch the Video: Exploring Our Solar System (9 minutes)

During the first millennium B.C., astronomy became more scientific. Middle Eastern and Chinese cultures observed the sun, stars and the planets more precisely, attempting to learn more about our position in the universe. They studied intently the rise and set times of the stars and planets, and developed calendars useful for agriculture. Star positions also became important tools in understanding directions, thereby aiding navigation. Although not always correct in its beliefs, the most mathematically influential society during this time period was ancient Greece; not only did thy think that the earth was the centre of the universe, but one philosopher stated in 434 B.C. that the sun was a ball of fire 60 kilometres in diameter, hovering 6500 kilometres above Earth’s surface. The Greeks did, however, use mathematics to estimate the circumference of the earth and developed extensive star catalogues. Around 130 B.C., Ptolemy wrote Almagest, a huge collection of astronomical data including mathematical models, information about eclipses, and planetary and stellar positions and movements. It remained the main astronomical almanac for hundreds of years, and was not seriously challenged until Copernicus disputed the geocentric model of the solar system in the 1500's.

By the 16th century, when the tools used to measure stellar positions gave relatively accurate results, astronomers began to note irregularities in the accepted model of the solar system and the night sky. In the early 1500s, Nicolaus Copernicus noted that the planets had slight discrepancies between their observed and presumed positions. When the theory that the planets orbited the earth in perfectly circular orbits could not account for the observed motions, Copernicus speculated that the sun was the centre of the solar system. This heliocentric model had been postulated in the third century B.C., but had not been taken seriously and was subsequently ignored.

A breakthrough for astronomy came with the invention of the telescope. The spyglass was invented in 1608, but an Italian named Galileo Galilei was the first to construct a telescope in 1610 and use it to look at the night sky. His small handheld refractor telescope did not provide sharp images and had a magnification of only 20 times, but what Galileo saw was unlike anything anyone had ever seen before. Over the first few months of observations Galileo had discovered more about the solar system and the universe than anyone had previously achieved. He first studied the sun and moon and discovered their surfaces were not perfect; the moon had numerous craters and mountains and there were visible “blemishes” which rotated around the surface of the sun. He observed the planets, noting that they were circular disks and not pinpoints of light like the stars. The phases of Venus were discovered and signified that planets shone by reflected sunlight. He also noticed the four large moons of Jupiter which are now named after him. The motion of the four satellites from one side of the planet to the other convinced Galileo that they were in orbit around Jupiter, proving that not every object in the sky was in orbit around the earth.

Watch Video: Geocentric vs Heliocentric Theories of Our Solar System (9 minutes)

Planetary Orbits

Galileo’s findings revolutionized astronomy as a science. It was not until Kepler and Newton backed the observations with mathematical calculations that the heliocentric model of the solar system was accepted as truth. While Galileo was making his breakthrough observations , Johannes Kepler used the accurate recorded observations of Brahe to develop a new planetary model, and formulated the three laws of planetary motion. Essentially the first law stated that the planets orbited the sun in an ellipse with the sun at one focus, the second that the orbital speed of a planet slows down the further it is from the sun, and the third gave a mathematical relationship between a planet’s orbital period and its distance from the sun (The square of the orbital period of the planets is proportional to the cube of their average distance from the sun). These simple but innovative laws were in agreement with the observed planetary movements, and allowed astronomers to calculate the distances from the planets to the sun.

Kepler's Three Laws of Planetary Motion

In the late 1600's a mathematician named Sir Isaac Newton developed his own three laws of motion involving forces, along with the universal law of gravity. Newton’s three laws were the law of inertia, the relation between the force applied to an object, the object’s mass, and its acceleration, and the third law is the famous “for every action there is an equal and opposite reaction”. His proposal of the law of gravity, which described mathematically that the force of attraction between two bodies was proportional to the product of their masses divided by the square of the distance between them, was a monumental concept and explained how the planets remained in orbit around the sun. The theory of gravity finally convinced astronomers that the sun was the centre of the solar system and governed the motions of the planets.

Acknowledgements: Canadian Space Agency

Part 2: Discussion / Opinion

1. Based on your knowledge and understanding of the major theories that exist of the formation of our Universe (above reading), go to the Blogger Site for Module #2 and provide at least one comment (50-100 words ideally) explaining which theory you believe to be most accurate and WHY. Please include this discussion post on a google doc as the D2L Discussions is still not working.

Part 3: Celestial Bodies Research 

In groups of 1 - 2, complete web research one of the following celestial bodies found in our solar system:

Sun, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune or Pluto

Asteroids, Meteroids and Comets (all three is one topic)

The final product will be a slideshow of your findings using google presentations or PREZI. Make sure to include the following information in your presentation: 

NOTE: More than one group can do the same topic.

For the Planets:

  • A minimum of 4 unique images of the object (include the website that you got the image from)
  • Physical description
  • Mean Distance from the Sun (in kms & AU)
  • Apparent Solar Magnitude
  • Orbital Period
  • Rotational Period (Equatorial)
  • Equatorial Diameter (Kms, Earth=1)
  • Mass (Kg, Earth=1)
  • Density
  • Satelites
  • Interesting Facts (Explorer satellites, composition etc..)
  • ONE Video link to a youtube video.

For the Sun:

  • A minimum of 4 unique images
  • Physical description
  • Diameter (Kms, Earth=1)
  • Mass (Kg, Earth=1)
  • Average surface temperature
  • Movement in the Galaxy
  • Interesting facts( Explorer satellites, other information, Type of Star etc..)
  • ONE Video link to a youtube video.
  • Other Interesting facts and information about our Sun.

For Asteroids, Meteroids and Comets:

  • A maximum of 4 images
  • Physical description
  • Mean Distance from the Sun (Kms (in millions, AU)
  • Apparent Solar Magnitude
  • Orbital Period
  • Diameter(Kms, Earth=1)
  • Mass (Kg, Earth=1)
  • Density
  • ONE Video link to a youtube video.
  • Other Interesting facts and information about Asteroids, Comets and Meteorites.
Interesting Facts(Explorer satellites, names of most famous, next visible from earth etc..)