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SAMPLE PAPER
2
Level 2 Earth and Space Science
2.6: Demonstrate understanding of stars and
planetary systems
Credits: Four
You should answer ALL parts of ALL questions in this booklet.
If you need more space for any answer, use the page(s) provided at the back of this booklet and
clearly number the question.
Check that this booklet has pages 2–9 in the correct order and that none of these pages is blank.
YOU MUST HAND THIS BOOKLET TO YOUR TEACHER AT THE END OF THE ALLOTTED TIME.
EXEMPLAR FOR EXCELLENCE
NOTE: These exemplars do not fully show Grade Score Marking (GSM) because of
the small sample of student scripts involved, and the absence of a cut score meeting
to determine grade boundaries. In 2012, level 1 2011 examination papers will have
exemplars marked full in accordance with GSM. These will be published on the
NZQA website when the assessment schedules are published.
OVERALL LEVEL OF PERFORMANCE
This exemplar has been generated by a subject expert not a candidate.
© New Zealand Qualifications Authority, 2012
All rights reserved. No part of this publication may be reproduced by any means without the prior permission of the New Zealand Qualifications Authority.
2
You are advised to spend 60 minutes answering the questions in this booklet.
QUESTION ONE: THE SUN
The Sun is at the centre of our solar system and provides the energy source for life on
Earth.
Explain in detail EACH of the stages (birth, life, and death) in the life cycle of the Sun. In your
explanation, you should make reference to the energy changes:
•
fuel use
•
mass
•
gravity.
You may draw a labelled diagram (s) in the box provided to support your answer.
During a stars birth a giant molecular cloud needs to be present. This may have come from
the remains of other exploded stars. The cloud begins to condense inwards due to gravity
or because of a trigger e.g. a supernova. As the cloud condenses the particles increase in
temperature due to increased friction. If the temperature reaches a specific point, about 1,
000, 000 kelvin then a proto-star will form.
At this point nuclear fusion begins and the process of hydrogen atoms fusing into helium
and releasing energy begins. The temperature increases to millions of degrees and matter
is converted into radiant energy. Our sun is a main sequence star. This means it uses
hydrogen as its fuel, our sun will spend the majority of its life, about 6 billion years, doing
this (H →He).
As our sun begins to run out of hydrogen it will increase in size and become a red giant.
This happens as it tries to increase its pressure, the core collapses and it begins fusing
helium to form carbon. Our sun does not have the mass required to fuse carbon. Therefore
the centre of the sun will collapse in on itself as gravity overcomes the internal pressure
outwards. The outer layers if the sun will be stripped off to form a new stellar nursery (giant
molecular cloud).
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The old core of the sun will become a white dwarf with no fuel source of its own. Eventually
the white dwarf will cool, become a black dwarf and die.
The candidate gives the linkages between the stages to
show how they progress, and gives a complete in-depth
life cycle of a star, focusing on fuel usage and gravity.
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QUESTION TWO: OUR SOLAR SYSTEM
Explain in detail how our solar system came to have inner and outer planets. In your answer, you
should consider the:
• formation of the solar system (including planets and their associated moons)
• size and composition of the inner and outer planets
• other features of the inner and outer planets related to their formation and ongoing existence.
The sun formed in a giant molecular cloud (GMC). It was at the centre of this cloud where
gravity was at its greatest that our sun was born. The rest of the GMC became a protoplanet disk. This was the birthplace for all our solar system’s planets and moons.
The planetary disk was in constant motion. This caused solar currents to form. The
movement/ spinning caused particles to get stuck together. Once they reached a certain
size, gravity held them together and planets began to form.
The inner planets (Mercury, Venus, Earth, and Mars) formed close to the sun. These planets
are made up of compounds (e.g. iron and nickel), which have high melting points. This is
because it is too hot for molecules with low melting points to be present (e.g. water and
methane). Also, any gases (H, He, CH4) were blown away by solar winds when our sun
ignited.
The inner planets ware comparatively small because their main compounds are relatively
rare in our universe. The inner planets all have similar characteristics;
• Solid surfaces
• Thin or non-existent atmospheres.
• Spin slowly compared to the outer planets.
None or few moons (e.g. Earth 1 and Mars 2) (moons were also blown off by solar winds,
Earths moon came from a solar collision, Mars’s moons are captures asteroids).
None of the inner planets have rings.
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The outer planets form further away from the sun in the proto-planetary disk where it was
cooler. Because of the decrease in temp, compounds like methane and other gases could
remain solid (this is the reversal of the inner planets, where lots of low melting point
compounds are commons compared to the high melting point compounds). This meant the
outer planets could grow in size and became the gaseous giants we know today.
The outer planets all have similar characteristics;
• Mainly made up of gases (due to being far enough away from the solar winds to keep
gases when the sun ignited).
• Have small solid/ liquid cores.
• All have similar atmospheres with lots of H, He, CH4.
• Many moons present (not blown away).
• All of the outer planets have orbiting rings of rock and dust.
The candidate gives a description of the
formation of the planets, linked to the presence
of moons, atmospheres, size etc. They also relate
composition to where planets are found, and
shows evidence of further reading.
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QUESTION THREE: USING THE HERTZSPRUNG-RUSSELL DIAGRAM
Red giants and white dwarfs are labelled on the Hertzsprung-Russell (HR) diagram below.
Explain in detail how the characteristics of red giants differ from those of white dwarfs. In your
explanation, you should consider:
•
the position of the red giants and white dwarfs on the Hertzsprung-Russell diagram
•
EACH of the following properties:
• temperature
• spectral class
• luminosity
• fuel source
• surface area
• mass.
Red Giants
Red Giants are found above the main sequence. They are bright stars (10 – 100 x brighter
than our sun), that have used up all of their hydrogen supply. This has caused their core to
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collapse and the outer layers to expand outwards so the He can be used as a fuel. Red
Giants try to fuse He → C. Red giants have a large surface area but their temperature is low
(2, 500 – 5, 000K) compared to their brightness. Red giants have high luminosity but low
temperature and are in the spectral class G, K or M.
When red giants run out of fuel, pressure blows off the outer layers and the very hot core is
left. This is called a white dwarf.
White Dwarf
White dwarfs form when a star dies. They don’t have a fuel source so are slowly cooling
over time. They range in temperature from 7, 500 – 30, 000 K. This is quite hot compared to
the red giants which are still burning fuel but it makes sense when you compare their
surface area and mass. White dwarfs have an extremely dense inner core, which means
they have a small surface area but a large mass, which causes high temperature. Looking at
the H/ R diagram you can tell that white dwarfs are not very bright (10 – 10, 000 x dimmer
than our sun) and they are of spectral type O, B, A, F. So white dwarfs are smaller, more
dense, and much dimmer than red giants. They are hotter than red giants and are in
different spectral classes (OBAF) as they give off different wavelengths of light (at the blue
end of the spectrum compared with the red end).
The candidate gives a discussion of fuel source,
which is essential as this information is not
provided on H/R diagram. The candidate also
explains the formation/operation of red giant
and white dwarf, and links characteristics to the
position on H/R diagram, but candidate compares
the types when the question asks how the
characteristics differ.
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