Space PhysicsOxford AQA IGCSE Physics: Topic test

20 questions, 54 marks

Oxford AQA IGCSE Physics

Space Physics topic test

Total 54 marks

Name

Class

Date

1
An amateur astronomer, observing a star cluster through a telescope, notices that one particular star appears redder and much larger than the surrounding stars. Records show this star has almost used up the hydrogen fuel in its core after spending billions of years on the main sequence.
(a)
What process, during the main sequence, released the energy that kept this star stable for billions of years?
[1 mark]
AFusion of helium nuclei into carbon
BFusion of hydrogen nuclei into helium
CRadioactive decay of heavy elements
DGravitational collapse of the core
(b)
Given this star is nearing the end of its main sequence and is similar in mass to the Sun, which stage is it probably about to become?
[1 mark]
AA black hole
BA neutron star
CA red giant
DA red supergiant
(c)
Explain, in terms of forces, why the size of a star's core stays stable during most of the main sequence.
[2 marks]
Total for question 1: 4 marks
2
A team observes a small moon of Jupiter and calculates that it takes 1.77 Earth days to complete one full orbit at a certain average distance from the planet. A class is asked to consider how this orbital period would change if the moon's distance from Jupiter increased.
(a)
What provides the centripetal force that keeps the moon in orbit around Jupiter?
[1 mark]
AGravitational attraction between the moon and Jupiter
BThe magnetic field of Jupiter
CThe moon's own rotation
DRadiation pressure from the Sun
(b)
If the moon's orbital radius were increased, moving it farther from Jupiter, what would happen to its orbital speed?
[1 mark]
AIt would increase
BIt would stay the same
CIt would decrease
DIt would become zero
(c)
Explain, in terms of the direction of the force acting on the moon, why the gravitational force changes the moon's direction but not its speed as it moves in a circular orbit.
[2 marks]
Total for question 2: 4 marks
3
A student science-fair project compares recorded emission-line wavelengths from three distant galaxies against the same spectral line's known laboratory wavelength of 500.0 nm, to investigate the relationship between distance and speed of recession. Galaxy P's line is measured at 500.7 nm, and Galaxy Q's line is measured at 502.1 nm.
(a)
Explain, using the Doppler effect, why the observed wavelength from a distant galaxy is longer than the laboratory wavelength of the same line, and state the name given to this shift.
[3 marks]
(b)
Using the data for Galaxy P (500.7 nm) and Galaxy Q (502.1 nm), explain which galaxy is moving away from Earth faster, and what this data, together with red-shift observations from many other galaxies, provides evidence for.
[4 marks]
Total for question 3: 7 marks
4
A space agency launches a probe that first uses gravity-assist manoeuvres to change its orbital path around the Sun before travelling far beyond the solar system, where its instruments record the red-shifted light from very distant galaxies.
(a)
Explain, using ideas about gravity and centripetal force, how the probe's speed and orbital radius around the Sun are related during a gravity-assist manoeuvre, and explain why a change in the probe's orbital speed results in a change in its orbital radius.
[6 marks]
(b)
Explain what red-shift is and how the probe's instruments could use it to determine that a distant galaxy is moving away from the solar system, and explain what conclusion scientists draw from the fact that more distant galaxies generally show greater red-shift.
[6 marks]
Total for question 4: 12 marks
5
A class studies historical records of a 'guest star' that appeared suddenly in the night sky a thousand years ago, becoming bright enough to see in daylight for weeks before fading. Modern telescopes show a rapidly expanding cloud of gas and dust, a supernova remnant, at the same position today, with an extremely dense object at its centre.
(a)
What type of star produces this kind of dramatic explosive event at the end of its life?
[1 mark]
AA star much less massive than the Sun
BA star similar in mass to the Sun
CAny star, regardless of mass
DA star much more massive than the Sun
(b)
What could the extremely dense central object left behind be?
[1 mark]
AA white dwarf
BA main sequence star
CA red giant
DA neutron star
(c)
Explain briefly what happens inside a massive star, in the stages before this explosive event, in terms of the fusion of heavier elements.
[2 marks]
Total for question 5: 4 marks
6
A university observatory tracks a newly discovered asteroid in the asteroid belt between Mars and Jupiter, and determines its orbital period around the Sun is about 4.6 Earth years, compared with Earth's own orbital period of 1 year.
(a)
Compared with Earth, is the asteroid's average distance from the Sun greater or smaller, given its longer orbital period?
[1 mark]
AGreater
BSmaller
CExactly the same
DDistance cannot be linked to orbital period
(b)
As an object's separation from the Sun increases, what happens to the gravitational force providing the centripetal force on it?
[1 mark]
AIt increases
BIt decreases
CIt stays the same
DIt reverses direction
(c)
Explain why an object with a greater average distance from the Sun has a lower orbital speed than one closer to the Sun.
[2 marks]
Total for question 6: 4 marks
7
A physics magazine explains that light detected from a particular distant galaxy has a spectral line shifted from its known laboratory wavelength of 434.0 nm to an observed wavelength of 437.6 nm, and states that the size of this shift can be used to estimate the galaxy's distance.
(a)
Explain what is meant by this being a red-shift, and what it tells us about the galaxy's motion.
[3 marks]
(b)
Calculate the increase in wavelength, and explain how this value could be used, together with observations of other galaxies at different distances, to provide evidence about how the universe is changing over time.
[4 marks]
Total for question 7: 7 marks
8
A physics class discusses that, several billion years from now, the Sun will swell into a red giant, expanding to a radius that may reach close to Earth's present orbit, before eventually losing its outer layers and shrinking to become a white dwarf with about half its current mass. The class considers how these changes would affect the orbits of any surviving planets.
(a)
Describe the life cycle stages the Sun will go through, from its current main sequence stage to becoming a white dwarf, and explain, in terms of forces, why the Sun will begin to expand into a red giant once it runs low on hydrogen fuel in its core.
[6 marks]
(b)
Explain, using ideas about gravitational force and mass, why a surviving planet's orbit would change once the Sun has lost roughly half of its mass in becoming a white dwarf, and explain whether the planet's new stable orbital speed at a similar distance would be higher or lower than before.
[6 marks]
Total for question 8: 12 marks

End of questions