AstronomyEdexcel GCSE Physics: Topic test

20 questions, 54 marks

Edexcel GCSE Physics

Astronomy topic test

Total 54 marks

Name

Class

Date

1
An artificial satellite is placed into a stable circular orbit around the Earth at a fixed height above the surface. Mission engineers later want to move the same satellite into a new, stable circular orbit that is much closer to the Earth, at a smaller orbital radius than before.
(a)
While the satellite travels in its original stable circular orbit at constant speed, which of the following correctly describes its velocity and the force acting on it?
[1 mark]
AIts velocity is continuously changing direction, because a resultant force (gravity) acts towards the centre of the orbit
BIts velocity is constant, because a constant force acts along its direction of travel
CIts velocity and the force acting on it are both exactly zero
DIts velocity is constant because no resultant force acts on it at all
(b)
For the satellite to move into a new, smaller stable circular orbit closer to the Earth, how must its orbital speed change compared with its original orbit?
[1 mark]
AThe orbital speed must decrease
BThe orbital speed must increase
CThe orbital speed must stay exactly the same
DThe orbital speed becomes zero in the new orbit
(c)
Explain why, for a stable circular orbit, the radius of the orbit must change if the orbital speed of a satellite changes.
[2 marks]
Total for question 1: 4 marks
2
An astronomy student is studying the life cycle of stars of a similar mass to the Sun. She learns that such stars form from a huge cloud of gas and dust, spend most of their lives in a stable phase fusing hydrogen into helium in their core, and later expand enormously once the hydrogen in their core begins to run out.
(a)
What is the name given to the huge cloud of gas and dust from which a star like the Sun initially forms?
[1 mark]
AA red giant
BA white dwarf
CA nebula
DA main sequence star
(b)
During the long, stable phase of a Sun-like star's life, what keeps the star's overall size roughly constant, neither collapsing nor expanding?
[1 mark]
AThe star's mass decreases to exactly zero during this stage
BFusion stops completely during this stable phase
CThe star is not affected by gravity while fusion is occurring
DThere is a balance between the outward force from thermal expansion (due to fusion) and the inward pull of gravity
(c)
Describe what happens to a Sun-like star after the hydrogen fuel in its core begins to run out, up to and including the final stage it reaches, naming the stages in order.
[2 marks]
Total for question 2: 4 marks
3
An astronomer studies light received from two distant galaxies, A and B. She compares the absorption lines in the spectrum of light from each galaxy with the same absorption lines measured from a source in the laboratory on Earth. She finds that the absorption lines from galaxy A have shifted towards the red end of the spectrum by a small amount, while the absorption lines from galaxy B, which is much further away, have shifted towards the red end of the spectrum by a much larger amount.
(a)
Explain what is meant by red-shift, and explain what the astronomer's observation that galaxy B shows a greater red-shift than galaxy A tells her about the relative distances and speeds of the two galaxies.
[3 marks]
(b)
Explain how this pattern, of more distant galaxies showing greater red-shift, provides evidence that the Universe is expanding, and explain why this pattern is observed for galaxies in every direction rather than just one part of the sky.
[4 marks]
Total for question 3: 7 marks
4
Two rival theories were once proposed to explain the origin of the Universe. The Steady State theory proposed that the Universe has always existed in roughly its current form, with matter continuously created to keep its average density constant as it expands. The Big Bang theory proposed that the Universe began from an extremely hot, dense point and has been expanding and cooling ever since. Scientists eventually favoured the Big Bang theory after further evidence was gathered.
(a)
Explain how both the Big Bang theory and the Steady State theory could each account for the observed red-shift of distant galaxies, and explain why red-shift evidence alone was therefore not enough to decide between the two theories.
[6 marks]
(b)
Explain what the cosmic microwave background (CMB) radiation is, and explain why its discovery led scientists to favour the Big Bang theory over the Steady State theory.
[6 marks]
Total for question 4: 12 marks
5
A robotic lander with a mass of 300 kg is launched from the surface of the Earth, where the gravitational field strength is 10 N/kg, and travels to the surface of the Moon, where the gravitational field strength is only 1.6 N/kg.
(a)
What happens to the mass of the lander as it travels from the Earth to the Moon?
[1 mark]
AThe mass stays exactly the same, at 300 kg
BThe mass increases, because gravity is weaker on the Moon
CThe mass decreases to zero once it leaves the Earth's atmosphere
DThe mass changes in proportion to the change in gravitational field strength
(b)
How does the weight of the 300 kg lander on the surface of the Moon compare with its weight on the surface of the Earth?
[1 mark]
AIts weight on the Moon is greater than on Earth
BIts weight on the Moon is smaller than on Earth, because the Moon's gravitational field strength is smaller
CIts weight is exactly the same on the Moon as on Earth
DThe lander has no weight at all on the Moon
(c)
Calculate the weight of the 300 kg lander on the surface of the Earth and on the surface of the Moon, showing your working and giving units, using W = m × g with g = 10 N/kg on Earth and g = 1.6 N/kg on the Moon.
[2 marks]
Total for question 5: 4 marks
6
An astronomy student compares the life cycle of the Sun with the predicted life cycle of a much more massive star, one many times heavier than the Sun, which has recently been observed by astronomers using a space telescope. Both stars begin their lives fusing hydrogen into helium in a stable phase, but the astronomer explains that the life cycle of the massive star will end very differently from the Sun's eventual white dwarf stage.
(a)
What is the general term for the stable, hydrogen-fusing phase that both the Sun and the much more massive star pass through, which each spends most of its lifetime in?
[1 mark]
AThe red giant phase
BThe nebula phase
CThe main sequence phase
DThe supernova phase
(b)
Which of the following correctly describes how the final stages of the massive star's life cycle differ from those of the Sun?
[1 mark]
AThe massive star expands into a red giant and then simply fades away, exactly like the Sun
BThe massive star's core never fuses any elements heavier than hydrogen, unlike the Sun's core
CThe massive star simply stops emitting any radiation once its hydrogen runs out, unlike the Sun
DThe massive star explodes as a supernova, which the Sun is not massive enough to do, potentially leaving behind a neutron star or black hole
(c)
State the final two stages, in order, that a star with a much greater mass than the Sun is expected to pass through, after its main sequence phase, up to its most likely final remnant.
[2 marks]
Total for question 6: 4 marks
7
An international space agency operates a large telescope in orbit above the Earth's atmosphere, instead of building an equally large telescope on the ground. Scientists explain that certain wavelengths of electromagnetic radiation arriving from distant objects in space are partly or completely absorbed by the Earth's atmosphere before they can reach a ground-based telescope.
(a)
Explain why placing a telescope in orbit above the Earth's atmosphere, rather than on the ground, allows astronomers to study a wider range of electromagnetic radiation from distant objects in space.
[3 marks]
(b)
Describe how observing methods used to study the Universe have changed over time, from simple visible-light observation to the use of a range of modern instruments including orbiting telescopes, and state one specific advantage a large radio telescope has over an optical telescope of a similar size.
[4 marks]
Total for question 7: 7 marks
8
A public astronomy talk covers two very different scales of the Universe. In the first part of the talk, the speaker describes how our own Sun formed billions of years ago and will eventually change over time. In the second part, the speaker describes how astronomers use observations of extremely distant galaxies to piece together the history of the entire Universe, from a much earlier and hotter state to the present day.
(a)
Describe the life cycle of the Sun from its formation to its predicted final stage, and explain, using the balance of forces, why the Sun remains a stable size for most of its lifetime.
[6 marks]
(b)
Explain how observations of red-shift and the cosmic microwave background from distant galaxies allow astronomers to build a picture of the Universe's history, from an earlier, hotter state to the present day, and explain why this evidence is currently best explained by the Big Bang theory.
[6 marks]
Total for question 8: 12 marks

End of questions