Science 9
Unit 5: Space
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Topic 7 – The Solar System Up
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The Sun
The Sun is made up of mostly hydrogen gas. It is 1.4 million km
in diameter. Its temperature is about 15 million degrees Celsius.
600t of hydrogen are converted, by nuclear fusion, into
helium per second. This is the energy released from the Sun.
The Sun emits charged particles in all directions. This solar
wind bombards the Earth at 400km/s, but the magnetic field
of the Earth protects us.
Traveling through The Solar System
The formation of our solar system is based on the ‘protoplanet
hypothesis’, which follows three steps:
1. A Nebula or a cloud of gas & dust in space begins swirling
2. Most of the matter (more than 90% of it) accumulates in the
center – forming the Sun
3. The remaining materials accumulate (forming planets) and
circle the Sun
The only way to see the detail on the planets in our solar system was
to send spacecraft up close to take pictures and send them back to the
Earth.
The Moon - The first “other world” seen up close was the Moon. On
July 17, 1969 Neil Armstrong and Edwin Aldrin landed on the moon for
a first hand look.
The Planets

The Inner Planets (Terrestrial)- Mercury, Venus, Mars and
the Earth - are considered the terrestrial planets because of their
composition.
The Outer Planets (Gas Giant) – Jupiter, Saturn, Uranus,
Neptune, and Pluto – are similar because of their gaseous
composition.
Planet Data see p. 412-415
Exploring the Outer Planets
(To boldly go where no human has gone before)
Observation equipment is sent out into space to explore distant areas
of our solar system. Space probes are unmanned satellites or
remote-controlled ‘landers’ that put equipment on or close to planets
where no human has gone before. Probes have done remote sensing
on Mercury and Jupiter, taken soil samples on Mars, landed on Venus,
and studied Saturn’s rings up close.
The most recent probes to explore Mars are still there. They are
Spirit and Opportunity. They are looking for evidence of water to
determine if Mars at one time could have sustained life. The only
place that has been explored by humans in space, other than our
Earth is the Moon.
Apollo 11 was the first landing and there have been many others
since. The next step is to establish a base for interplanetary manned
missions to Mars.
Voyager Today (note: the following is extra info)
As of April 4, 2007, Voyager 1 is over 15.18×109 km or 101.4 AU
from the Sun, and has thus entered the heliosheath, the termination
shock region between the solar system and interstellar space, a vast
area where the Sun's influence gives way to the other bodies in the
galaxy. If Voyager 1 is still functioning when it finally passes the
heliopause, scientists will get their first direct measurements of the
conditions in the interstellar medium. At this distance, signals from
Voyager 1 take more than thirteen hours to reach its control center.
Voyager 1 is on a hyperbolic trajectory and has achieved escape
velocity, meaning that its orbit will not return to the inner solar
system. Along with Pioneer 10, Pioneer 11, and Voyager 2, Voyager 1 is an
interstellar probe.
Voyager 2 launched on August 20, 1977. It is identical to its sister
Voyager program craft, Voyager 1, but unlike Voyager 1, Voyager 2
followed a slower trajectory that allowed it to be kept in the ecliptic so
that it could be sent to Uranus and Neptune by means of gravity assist
during the 1981 encounter at Saturn. Because of this, Voyager 2 could
not see the moon Titan up close like its twin, but it allowed the probe
to become the first spacecraft to travel to Uranus and Neptune, thus
completing a portion of the so-called Planetary Grand Tour, a rare
geometric arrangement of the outer planets that only occurs once
every 176 years.
Distribution of Space and Matter
Elliptical paths can help astronomers and scientists to trace and predict
where bodies in space are, have been and will be in the future. The
understanding of orbits has led to the discovery of many different
comets. NASA tracks asteroids, comets and meteors that have been
discovered by observatories and amateur astronomers.
Astronomical unit is used for measuring ‘local’ distances in the solar
system. It is equal to the distance from the center of the Sun to the
center of the Earth (approximately 149,599,000 kms).
Light year is equal to the distance light travels in 1 year
(approximately 9.5 trillion kms). It is used for longer distances – to
stars and galaxies. The distance to our nearest star, Proxima
Centauri is a little over 4 light years.
Comets- a celestial body made of ice and dust that orbits the Sun. It
has a bright centre and long faint tail that always points away from the
Sun. (ex. Halley’s Comet- we see it every 76 years- its last pass was
in 1986)
Meteors and Meteorites- a meteor is a piece of rock or metal that
enters the Earth’s atmosphere and glows brightly from the friction.
(Ex. Shooting stars) A meteorite is a meteor that has landed on the
Earth’s surface.
Looking into the Past?
When you view an object in the sky you are seeing it as it was in the
past. It has taken the light a very long time to reach the Earth. Light
from the Sun takes about 5 minutes to reach the Earth, whereas light
from Pluto takes about 5 hours. The farther away, the longer light
takes to reach the Earth. Light from the stars in the center of the
universe takes about 25,000 years to reach the Earth. The Hubble
telescope is capturing light from 12 billion years ago.
Stars
Stars are born in a nebula. A star is a hot, glowing ball of gas (mainly
hydrogen) that gives off light energy. Stars vary in their
characteristics. Very hot stars look blue, while cooler stars look red. In
the 1920’s, Ejnar Hertzsprung and Henry Norris Russell compared the
surface temperature of stars with its brightness (luminosity). They
graphed their data to show the relationship between brightness and
temperature of stars was not random. The process of ‘star-building’ is
known as fusion (when hydrogen is converted to helium), which
releases great amounts of energy and radiation.
Topic 7 Assignment
Vocabulary:
Solar wind
Inner planet
Outer planet
Proto-planet hypothesis
Space probe
Nebula
NASA
Fusion
Comet
Meteor
Meteorite
Use your notes and textbook to answer the following
questions.
1. Write out the protoplanet hypothesis.
The solid material in the the gas cloud clumped into
protoplanets that were somewhat like asteroids. The larger clumps
were hit by the smaller clumps until we got the 8 planets that we
have today. The 4 largest ones were able to retain hydrogen and
helium in their atmosphere.
2. List 3 interesting facts about the Sun that you read about:
The sun has a large black spot, which proves it’s rotation.
The Sun is by far the largest object in the solar system. It contains
more than 99.8% of the total mass of the Solar System
The temperature is 15.6 million Kelvin
3. What is solar wind?
The solar wind is a stream of energized, charged particles, primarily
electrons and protons, flowing outward from the Sun, through the
solar system at speeds as high as 900 km/s and at a temperature of 1
million degrees
4. When did the first astronauts land on the moon? Who were
they?
Neil Armstrong and Buzz Aldrin during July 20, 1969.
5. Which planet is most similar to Earth? Why?
In terms of size, average density, mass, and surface gravity, Venus is
very similar to Earth.
6. Venus is considered Earth’s twin, yet we would probably not
survive on Venus. Why?
Since Venus is the closest planet to the sun, the temperature is way to
hot for any life to live there.
7. How does the Sun release energy?
A nuclear fusion builds up, and overtime causes the planet to release
nuclear energy.
8. Why do many of the inner planets show evidence of heavy
cratering?
Because the Inner planets are all composed of solid matter.
9. What are Voyager I and II and why are they special.
They both went the furthest out, and reached many planets such as,
Uranus and Neptune.
10.
Why are comets called dirty snowballs?
because they go through space collecting dirt and stuff to build
themselves up
11.
What is the difference between a meteor and a meteorite?
Astronomers call "shooting stars" meteors. They are small bits of
"dust" from space that burn up in the atmosphere. A meteorite is a
piece of rock or other material from space that actually lands on Earth.