Download Formation of the Solar System

CGF 3M Assignment 2
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
external websites are highlighted in BLUE.
Part 1: Background Information and Terminology
Your Task: Read information, make point form notes in your notebook (google
docs) and follow all hyper-links to related sites.
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
URL: NASA
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
A recreation of a the Milky Way galaxy
own gravity. At this point, the clump
becomes a protogalaxy. Astronomers
Image Acknowledgements: Canadian Space
hypothesize that protogalaxies consist
Agency
of both dark matter and normal
URL: Canadian Space Agency
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.
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 that 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
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.
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 theorydescribes 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, comets, asteroidsand 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.
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
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 mode 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.
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 1600s 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: Individual Written task
1. Based on your knowledge and understanding of the major theories that exist of the
formation of our Universe (above reading), provide at least one comment (50 words)
explaining which theory you believe to be most accurate and WHY.
Part 3: Group Assignment
1.
Group Assignment
In groups of 2, 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)
Be sure to get the approval of your choice by Mr. White before you begin the
websearch. The final product will be a slideshow presentation of your findings using
presentation software of your choice (ex. Powerpoint or Corel Presentations). Make
sure to include the following information in your presentation:
For the Planets:



A maximum of 4 images of the planet (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..)
For the Sun:







A maximum of 4 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..)
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
Interesting Facts (Explorer satellites, names of most famous, next visible from earth
etc..)
DO NOT JUST CUT AND PASTE INFORMATION. TAKE TIME TO MAKE YOUR
PRESENTATION VISUALLY APPEALING AND UNIQUE!
Resources:
http://www.eightplanetsfacts.com/ The Eight Planets
http://www.nineplanets.org/ Welcome to the Planets
http://pds.jpl.nasa.gov/planets Moons and Planets, Solar System Exploration, NASA
http://sse.jpl.nasa.gov/planets/index.cfm Moons, Solar System Exploration, NASA