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NCEA Level 2 Science (90764) 2011 — page 1 of 3
Assessment Schedule – 2011
Science: Describe the nature and life cycle of stars (90764)
Evidence Statement
Evidence Achievement Achievement with Merit Achievement with Excellence Question One
• Within the nebulae gas cloud, gravitational forces cause dust
and gas particles to come together.
Describes aspects of a brown dwarf
OR
describes aspects of star formation.
Eg:
• Gravitational forces cause dust and
gas to join together.
• Main sequence star has sufficient
mass that enables fusion to take
place.
• Hydrogen nuclei fuse to give
helium.
• Brown dwarf has insufficient mass
• Insufficient gravitational forces to
begin the fusion process.
• Brown dwarf has no luminosity.
• Sun is luminescent.
• Description of fusion (increased
pressure leading to an increase in
temperature).
Describes the sequence of brown
dwarf formation
OR
The sun formation.
OR
Partial description of a brown dwarf
and the sun formation.
Eg:
(Protostars) form within nebulae gas
and dust clouds under influence of
gravity.
Main sequence star has sufficient
mass that gravitational forces cause
the hydrogen nuclei to fuse and
release energy (electromagnetic
radiation). The Sun is luminescent.
Eg:
Protostars form within nebulae gas
clouds under influence of gravity.
• Brown dwarf has insufficient mass
and therefore insufficient
gravitational forces to begin the
fusion process. Brown dwarf does
not release same energy/ no
luminosity as main sequence star.
Discusses formation of Sun and
brown dwarf and explains why brown
dwarf has not developed into a star
like our sun.
• Protostars are formed.
• Gravitational forces cause the hydrogen in the star to begin
to fuse. (4 hydrogen atoms to form one helium atom.)
• Fusion process causes the star to begin to release energy in
the form of electromagnetic radiation across the spectra.
• The star has sufficient mass to become a main sequence star.
• Brown dwarf has insufficient mass and therefore insufficient
gravitational forces to begin the fusion process.
• Brown dwarfs emit only infra-red radiation and have no
luminosity. Evidence can be obtained from a
labelled diagram.
Evidence can be obtained from a
labelled diagram.
(Protostars) form within nebulae gas
clouds under influence of gravity.
Main sequence star has sufficient
mass that gravitational forces cause
the hydrogen nuclei to fuse and
release energy and luminance like the
Sun (electromagnetic radiation). On
the other hand a brown dwarf has
insufficient mass to start fusion
process of hydrogen nuclei. Brown
dwarfs are small in comparison to the
sun and (emit only infra-red
radiation). No luminosity.
Evidence can be obtained from a
labelled diagram.
NCEA Level 2 Science (90764) 2011 — page 2 of 3
Question Two:
• Sirius A is a blue / white star in the main sequence.
• Sirius B is a white dwarf.
• Sirius A is much hotter star, burning fuel more rapidly.
• Sirius A is more luminous due to the faster fuel burning rate
and size.
• Luminosity is the amount of light being given off by the star.
• White dwarf is greater in mass than the main sequence star,
but smaller in size.
• White dwarf has no fuel to burn. Seen as result of radiation
release.
• Mass of a white dwarf is very dense causing a change in spin
of the larger star.
Describes the properties of two stars:
Evidence may come from Sirius A
OR
Sirius B
OR
Wobble
Sirius A
• luminous
• hotter star as result of more rapid
fuel use.
• large in size
• lower gravitational force
• smaller in density.
Sirius B
• not luminous.
• smaller star in size.
• no fuel
• high gravitational field
• higher in density.
Wobble
Sirius B has a higher gravitational
force, which causes Sirius A to
wobble as Sirius B orbits Sirius A.
Evidence may be obtained from a
labelled diagram
Contrasts properties of Sirius A and B
OR
Wobble and mass
Eg:
Hydrogen use in Sirius A is more
rapid hence the luminosity and higher
star temperature.
Sirius B has no fuel to burn hence
lower luminosity.
Contrasts properties and explains why
Sirius A wobbles.
Eg:
Hydrogen use in Sirius A is more
rapid hence the luminosity and higher
star temperature. Sirius B has no fuel
to burn hence lower luminosity
As the mass of Sirius B is denser thus
higher gravitational force causes
Sirius A to wobble as Sirius B orbits
Sirius A.
Star types required
OR
Higher mass of Sirius B (higher
gravitational force) causes Sirius A to
wobble as Sirius B orbits Sirius A.
Evidence can be obtained from a
labelled diagram.
Evidence can be obtained from a
labelled diagram
NCEA Level 2 Science (90764) 2011 — page 3 of 3
Question Three:
• Supernova originates from a large red giant / super giant.
• Hydrogen runs out.
• When it cannot fuse iron, the core will collapse and then
explode.
• Star core collapses due to gravity and the outer layers of the
star are exploded out.
• A very dense neutron star or a black hole remains.
• The variability in brightness caused by the gases and plasma
exploding off the surface.
Describes origin and outcome of a
supernova.
• originates from an exploding large
red giant
• partial explanation of the cause of a
supernova
• a black hole or neutron star is left.
OR
Describes the origin OR outcome and
the steps that form a supernova.
Evidence may be obtained from a
labelled diagram.
Explanation of the origin and outcome
and the steps that form a supernova
OR
Describes the origin or outcome and
the steps that form a supernova.
AND
Explains the appearance of a
supernova.
OR
Explains gas clouds are the birthplaces for new stars.
Evidence may be obtained from a
labelled diagram.
Discusses the formation and outcome
of a supernova and explains the
appearance of a supernova.
OR
Explains gas clouds are the birth
places for new stars.
Supernova gives out clouds of gases
and plasma exploding off its surface.
AND
These gas clouds are the birth places
for new stars.
AND
After this process ceases, a black hole
or a dense neutron star remains (detail
provided about the formation).
Eg:
The core of the star then collapses,
combining protons and electrons to
form neutrons. Hence the name
“neutron star”.
If the star is too massive, the
gravitational force of the collapse is
so powerful, a black hole is created.
Evidence may be obtained from a
labelled diagram.
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
2 A 2 M OR 1 E + 1 A 2 E OR 1 E + 2 M