1a3 marks
Explain the term galactic redshift.
1b2 marks
Explain why galactic redshift is considered as evidence supporting the Big Bang theory.
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Stars & The Universe (CIE IGCSE Physics)
Topic Questions
2a1 mark
Define the Hubble Constant.
2b3 marks
State the equation for the Hubble constant and define all the variables.
2c1 mark
State the equation to calculate the age of the Universe.
2d4 marks
The Hubble constant is estimated to be 2.2 × 10–18 s–1
Calculate the age of the Universe in years.
1 year = 3.15 × 107 s
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3a1 mark
Starting with the largest, list the following in order of decreasing size
| Galaxy Sun Universe Jupiter |
3b2 marks
State the stages in the life cycle of a star the size of the Sun after the main sequence in the gaps below
Main sequence → ................................... → ...................................
3c4 marks
State the stages in the life cycle of a star much greater than the size of the Sun after the main sequence in the gaps below
Main sequence → ................................... → ................................... → ................................... or ...................................
3d2 marks
Explain what may form in nebulae created by a supernova.
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4a1 mark
State the approximate diameter of the Milky Way in light years.
4b2 marks
Extended
Nuclear fusion occurs in the core of a stable star.
Complete the sentence explaining nuclear fusion.
Nuclear reactions in the core of a star involve the fusion of ........................... into ...........................
4c2 marks
The Virgo A galaxy and Messier 90 galaxy are 6.2 × 1020 km and 5.5 × 1020 km from Earth respectively. They are both moving away from Earth.
State and explain which galaxy is moving faster away from Earth.
4d1 mark
Extended
Explain how the distance of a far galaxy can be determined.
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5a6 marks
Rearrange the stages of the life cycle of a star into the correct order.
| 1 | white dwarf |
| 2 | planetary nebula |
| 3 | protostar |
| 4 | main sequence star |
| 5 | interstellar clouds of gas and dust (stellar nebula) |
| 6 | red giant |
5b1 mark
A star can be in its main sequence phase for billions of years.
Fig 1.1 shows the forces acting on the Sun during this stable stage of its life cycle.
(i)
State the name of the force pulling inwards.
[1]
(ii)
Explain what causes the force pushing outwards.
[1]
5c2 marks
Two stars, Alpha Centauri B and Betelgeuse are 0.9 and 16.5 solar masses respectively.
State which star could eventually become a neutron star. Explain your reasoning.
1 solar mass = mass of the Sun
5d1 mark
State what is meant by a supernova.
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1a1 mark
Extended
Edwin Hubble was an American scientist who studied galactic recession.
Define the Hubble constant, H0.
1b2 marks
Extended
State the current value of the Hubble constant.
1c4 marks
Extended
The Andromeda galaxy is the Milky Way's largest galactic neighbour. The Andromeda galaxy is approximately 2.5 million light years from Earth.
Calculate the speed with which the Andromeda galaxy is receding from Earth. You should give your answer in km/s.
............................................................... km/s
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2a4 marks
Extended
State and explain the two pieces of evidence which support the Big Bang Theory of the origin of the Universe.
2b4 marks
Calculate the distance of 50 light-years in metres.
c = 3.0 × 108 m/s.
2c5 marks
Extended
Redshift measurements show that a galaxy is receding from Earth at a speed of 32 000 km/s.
Use Hubble's Law to calculate how many light-years the galaxy is distant from the Solar System.
Take the Hubble constant to be 2.2 × 10-18 s–1.
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3a2 marks
Extended
Explain what type of radiation the CMBR will eventually change into over the next billion years
3b4 marks
Extended
Scientists measure the wavelength of the radio waves from galaxy A travelling at 260 km/hr away from Earth to be 63.2 m. Sometime later, the wavelength is measured to be 63.4 m.
The wavelength of the radio waves from galaxy B is initially measured to be 63.4 m and at the same time later, measured to be 63.8 m.
Calculate the velocity of galaxy B.
velocity of galaxy B = ...................................... m/s
3c3 marks
Extended
By measuring the red-shift, Hubble was able to calculate the speed at which the galaxies are moving away from the Earth. He was also able to calculate the distance of these galaxies from the Earth. The graph in Fig 1.1 shows some of the data calculated by Hubble.
Fig 1.1
The graph in Fig 1.1 was used to calculate the most up-to-date value of the Hubble constant, H0.
Megaparsecs are a unit for large distances commonly used in Astronomy and Cosmology. 1 megaparsec = 3.1 × 1022 m.
Calculate H0 in km/s megaparsec.
3d3 marks
Extended
Show that H0 is roughly 2.0 × 10–18 s–1.
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4a4 marks
The ‘big bang’ theory is one theory explaining the origin of the Universe.
Fig 1.1
(i)
Sketch the graph of the size of the Universe with time on Fig 1.1.
[2]
(ii)
Explain how your graph in part (i) supports the Big Bang Theory.
[2]
4b5 marks
Extended
Describe and explain the important properties of the CMBR. Explain their significance as evidence for the evolution of the Universe.
4c2 marks
Extended
Explain why our understanding of the very earliest moments of the Universe is unreliable.
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5a2 marks
Extended
Nuclear fusion reactions in the Sun fuse hydrogen to make helium.
In the Solar System, the inner planets, such as the Earth, contain elements which are heavier than the elements hydrogen and helium.
Explain how this can be the case.
5b3 marks
Extended
From the data collected, a graph can be drawn that links the speed of a galaxy with the distance of the galaxy from the Earth.
Fig 1.1
Describe how the visible light spectrum from galaxy Q looks different from the visible light spectrum from galaxy P.
5c3 marks
Extended
A third galaxy, R, seems to be travelling away from the Earth at about 110 000 km/s.
Estimate how far galaxy R might be from the Earth, showing how you use the graph to do this.
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1a3 marks
The Sun is our nearest star.
(i)
State the three main forms of electromagnetic radiation emitted by the Sun.
[2]
(ii)
State the two main elements that are found in the Sun.
[1]
1b3 marks
State and explain what can be deduced from the ‘redshift’ observed by astronomers in the light from all distant galaxies.
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2a3 marks
Extended
Describe and explain how a stable star is formed.
2b1 mark
Extended
Describe and explain what can be deduced from cosmic microwave background radiation (CMBR).
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3a5 marks
Extended
Some main sequence stars become black holes.
Describe the evolution of a main sequence star to the point at which it becomes a black hole.
3b2 marks
Extended
State and explain whether the Sun will eventually become a black hole.
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4a2 marks
The visible part of the electromagnetic spectrum from a star includes a dark line. This line is at a specific wavelength.
Fig 1.1 shows the position of the dark line in the spectrum from the Sun and in the spectrum from two different galaxies, galaxy A and galaxy B.
Explain what the spectrum ‘shifts’ of the dark lines tells us about the direction of the galaxies.
4b2 marks
State which galaxy is:
(i)
is moving faster.
[1]
(ii)
is further away.
[1]
4c4 marks
Extended
Galaxy A is 150 000 × 109 m away.
Calculate its recession velocity.
Hubble constant = 2.2 × 10–18 s–1
4d2 marks
Extended
A galaxy C is twice as far as galaxy A.
Determine the recession velocity of galaxy C.
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5a2 marks
Extended
Describe nuclear fusion in stars.
5b5 marks
Extended
Derive the distance of 1 light year in metres.
c = 3.0 × 108 m/s
5c2 marks
Extended
The Milky Way is approximately 100 000 light years in diameter.
Calculate the time it would take a spacecraft travelling at the speed of light to travel from one side of the Milky Way to the other.
time = ......................................... s
5d4 marks
Below are some statements related to Cosmology.
- Galaxies are made of up millions of stars
- The Sun is a planet because it has a core
- Other stars that make up the Milky Way are much further away from the Earth than the Sun is from the Earth
- There may be other galaxies in the Milky Way
State all of the statements that are false and explain why.
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