Stars and the Universe
Chapter 28 MCQs
Stars and the Universe
Assume speed of light = 3.0 × 10⁸ m/s where needed.
Assume 1 year = 3.2 × 10⁷ s where needed.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
1
Which statement correctly describes the Sun?
A a planet in the Milky Way
B a star in the Milky Way
C a galaxy in the Universe
D a moon orbiting Earth
2
Which statement best describes a galaxy?
A a planet and its moons only
B a large collection of stars, gas and dust held together by gravity
C a single star surrounded by planets
D a small rock orbiting the Sun
3
The Milky Way is:
A the Solar System
B a planet
C a galaxy containing the Solar System
D the whole Universe
4
Which statement best describes the Universe?
A the Sun and its planets only
B Earth, the Moon and the Sun only
C all matter, energy, space and time
D only the stars visible without a telescope
5
A light-year is a unit of:
A time
B distance
C speed
D energy
6
Which definition of one light-year is correct?
A the time taken by light to travel from the Sun to Earth
B the distance travelled by light in one year
C the speed of light in one year
D the time taken by Earth to orbit the Sun
7
What is the approximate distance of 1 light-year?
A 3.0 × 10⁸ m
B 3.2 × 10⁷ m
C 9.6 × 10¹⁵ m
D 9.6 × 10⁻¹⁵ m
8
A star is 5.0 light-years from Earth.
Approximately how far away is it in metres?
A 1.9 × 10¹⁵ m
B 4.8 × 10¹⁶ m
C 1.5 × 10⁸ m
D 1.6 × 10⁸ m
9
Light from a star takes 12 years to reach Earth.
How far away is the star?
A 12 km
B 12 light-years
C 12 m/s
D 12 years per metre
10
A galaxy is 2.5 × 10⁶ light-years away.
What does this mean?
A light from it takes 2.5 × 10⁶ years to reach Earth
B the galaxy is 2.5 × 10⁶ years old
C the galaxy moves at 2.5 × 10⁶ m/s
D the galaxy contains 2.5 × 10⁶ stars exactly
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
11
A telescope observes a galaxy 100 million light-years away.
What is true about the image seen?
A it shows the galaxy as it is now
B it shows the galaxy as it was 100 million years ago
C it shows the galaxy as it will be 100 million years in the future
D it proves light travels instantly
12
Why are light-years useful in astronomy?
A astronomical distances are extremely large
B light-years are smaller than metres
C stars move only in light-years
D light-years measure temperature directly
13
Which sequence correctly shows increasing size scale?
A Earth → Solar System → Milky Way → Universe
B Universe → Milky Way → Solar System → Earth
C Earth → Milky Way → Solar System → Universe
D Solar System → Earth → Universe → Milky Way
14
Which object is outside the Solar System but inside the Milky Way?
A the Moon
B Mars
C another star in our galaxy
D Earth’s artificial satellite
15
Which statement about stars is correct?
A stars produce energy by nuclear fusion
B stars produce energy only by burning coal
C stars are planets reflecting sunlight
D stars have no mass
16
In a main sequence star like the Sun, the main nuclear reaction is:
A hydrogen nuclei fuse to form helium
B helium nuclei split into hydrogen
C iron nuclei fuse to form oxygen
D electrons fuse with neutrons to form light
17
Why does nuclear fusion in stars release energy?
A mass is converted into energy during fusion
B stars absorb energy from nearby planets
C gravity disappears inside the star
D atoms stop moving completely
18
Which condition is needed for nuclear fusion in a star?
A very low temperature and low pressure
B very high temperature and high pressure
C no gravity
D complete vacuum with no nuclei
19
A stable main sequence star is in equilibrium because:
A gravitational forces inward are balanced by outward pressure from fusion/radiation
B gravity acts outwards and radiation acts inwards
C no forces act inside the star
D the star has no mass
20
What is the main source of the Sun’s energy?
A chemical burning of gases
B nuclear fusion in its core
C reflection of light from planets
D radioactive decay of uranium only
21
A star forms from a cloud of gas and dust called a:
A galaxy
B nebula
C comet
D black hole
22
What causes a nebula to begin collapsing to form a star?
A magnetic repulsion only
B gravitational attraction between particles
C sunlight from Earth
D friction with empty space
23
As a gas cloud collapses to form a protostar, what happens to its temperature?
A decreases to absolute zero
B increases as gravitational potential energy is transferred to internal energy
C remains exactly constant forever
D becomes negative in kelvin
24
A protostar becomes a main sequence star when:
A nuclear fusion of hydrogen begins steadily in the core
B all gas escapes into space
C the star becomes a planet
D the star stops producing energy
25
Which sequence correctly shows the early formation of a star?
A nebula → protostar → main sequence star
B main sequence star → protostar → nebula
C white dwarf → nebula → protostar
D black hole → main sequence star → nebula
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
26
A star spends most of its lifetime as a:
A protostar
B main sequence star
C planetary nebula
D supernova
27
What eventually happens when a main sequence star like the Sun runs low on hydrogen in its core?
A it becomes a red giant
B it immediately becomes a black hole
C it becomes a planet
D it disappears without releasing energy
28
A star with a similar mass to the Sun is most likely to end as a:
A neutron star
B black hole
C white dwarf
D supernova remnant only
29
Which sequence is most suitable for the life cycle of a Sun-like star?
A nebula → protostar → main sequence → red giant → white dwarf
B nebula → protostar → main sequence → red supergiant → black hole
C main sequence → nebula → protostar → white dwarf
D protostar → black hole → red giant → main sequence
30
A star much more massive than the Sun is most likely to become, after its main sequence stage:
A red supergiant
B white dwarf directly
C small rocky planet
D comet
31
A very massive star may end its life as:
A a white dwarf only
B a neutron star or black hole
C a low-mass asteroid
D a main sequence star forever
32
Which event is associated with the death of a massive star?
A supernova explosion
B melting
C evaporation into water vapour
D reflection from a mirror
33
Which sequence is most suitable for a massive star?
A nebula → protostar → main sequence → red supergiant → supernova → neutron star/black hole
B nebula → protostar → white dwarf → main sequence
C main sequence → red giant → white dwarf only
D planet → nebula → black hole → Sun
34
What is a black hole?
A a region where gravity is so strong that not even light can escape
B a planet with no atmosphere
C a dark cloud that emits visible light strongly
D a type of comet near Earth
35
Why can a black hole be difficult to observe directly?
A it reflects all visible light perfectly
B it emits no light that escapes from within the event horizon
C it has no gravitational effect
D it is always inside Earth’s atmosphere
36
A white dwarf is:
A the hot dense remaining core of a low/medium mass star
B a large cloud of hydrogen before star formation
C a galaxy with few stars
D a planet made only of ice
37
A neutron star is:
A a dense remnant made mostly of neutrons after some supernovae
B a small moon orbiting a planet
C a star before fusion starts
D a star made only of electrons
38
Which final object is most likely if the collapsed core after a supernova is extremely massive?
A black hole
B white dwarf
C comet
D asteroid belt
39
Which statement about supernovae is correct?
A they can spread heavy elements into space
B they occur in every star once per day
C they are caused by planets colliding with moons only
D they produce no radiation
40
Why are supernovae important for the formation of planets and life?
A they create and spread heavy elements into space
B they remove all elements heavier than hydrogen from the Universe
C they stop gravity from acting
D they convert all matter into visible light permanently
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
41
Light from a galaxy is observed to have its spectral lines shifted towards longer wavelengths.
This is called:
A blueshift
B redshift
C total internal reflection
D beta decay
42
Redshift of light from a distant galaxy suggests that the galaxy is:
A moving towards Earth
B moving away from Earth
C stationary relative to Earth
D turning into a planet
43
A galaxy shows a larger redshift than another galaxy.
What does this usually suggest?
A it is moving away faster
B it is closer and slower
C it is moving towards Earth faster
D it contains no stars
44
The light from most distant galaxies is redshifted.
What does this provide evidence for?
A the Universe is expanding
B Earth is at the centre of the Universe
C light cannot travel through space
D stars are not real objects
45
Which observation supports the idea that the Universe began in a hot dense state?
A cosmic microwave background radiation
B alpha particles stopping in paper
C sound waves travelling through air
D compass needles pointing north
46
Cosmic microwave background radiation is:
A leftover radiation from the early Universe
B radiation from mobile phones only
C light reflected from the Moon
D alpha radiation from smoke detectors only
47
According to the Big Bang theory, the Universe:
A began from a hot, dense state and has been expanding
B has always been exactly the same size and temperature
C began when Earth exploded
D contains only the Solar System
48
A galaxy is moving away from Earth at 1.2 × 10⁷ m/s.
Its distance is 4.0 × 10²³ m.
Using speed / distance, what value is obtained?
A 3.0 × 10⁻¹⁷ s⁻¹
B 4.8 × 10³⁰ s⁻¹
C 3.3 × 10¹⁶ s
D 4.8 × 10¹⁵ m/s
49
Two distant galaxies are observed.
Galaxy X has a small redshift.
Galaxy Y has a larger redshift.
Which conclusion is usually correct?
A Y is receding faster than X
B X is receding faster than Y
C both are moving towards Earth
D redshift gives no information about motion
50
A student says, “Galaxies are redshifted because their light loses energy by travelling through tired space, so expansion is not needed.”
Which correction is best for exam physics?
A redshift of distant galaxies is taken as evidence that galaxies are receding and the Universe is expanding
B redshift means galaxies are turning blue
C redshift proves stars do not emit light
D redshift is caused by sound waves in space
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
Chapter 28 Answer Key
Stars and the Universe
| Q | Ans | Q | Ans | Q | Ans | Q | Ans | Q | Ans |
|---|---|---|---|---|---|---|---|---|---|
| 1 | B | 11 | B | 21 | B | 31 | B | 41 | B |
| 2 | B | 12 | A | 22 | B | 32 | A | 42 | B |
| 3 | C | 13 | A | 23 | B | 33 | A | 43 | A |
| 4 | C | 14 | C | 24 | A | 34 | A | 44 | A |
| 5 | B | 15 | A | 25 | A | 35 | B | 45 | A |
| 6 | B | 16 | A | 26 | B | 36 | A | 46 | A |
| 7 | C | 17 | A | 27 | A | 37 | A | 47 | A |
| 8 | B | 18 | B | 28 | C | 38 | A | 48 | A |
| 9 | B | 19 | A | 29 | A | 39 | A | 49 | A |
| 10 | A | 20 | B | 30 | A | 40 | A | 50 | A |
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
Detailed Explanations
1. B
-
The Sun is a star.
-
It is located in the Milky Way galaxy.
-
It is not a planet, moon or galaxy.
2. B
-
A galaxy is a huge collection of:
-
stars
-
gas
-
dust
-
dark matter
-
-
These are held together by gravity.
3. C
-
The Milky Way is the galaxy that contains our Solar System.
-
The Solar System is only a tiny part of the Milky Way.
-
The Milky Way is not the whole Universe.
4. C
-
The Universe means everything:
-
matter
-
energy
-
space
-
time
-
-
It includes all galaxies, stars, planets and radiation.
5. B
-
A light-year is a unit of distance, not time.
-
The name traps students because it contains “year”.
-
Sneaky little villain of astronomy MCQs.
6. B
-
One light-year is the distance travelled by light in one year.
-
It is used because astronomical distances are extremely large.
7. C
-
Distance = speed × time
-
1 light-year = 3.0 × 10⁸ × 3.2 × 10⁷
-
= 9.6 × 10¹⁵ m
-
Answer = 9.6 × 10¹⁵ m
8. B
-
1 light-year = 9.6 × 10¹⁵ m.
-
5.0 light-years:
-
5.0 × 9.6 × 10¹⁵
-
= 48 × 10¹⁵
-
= 4.8 × 10¹⁶ m
-
9. B
-
If light takes 12 years to reach Earth, the star is 12 light-years away.
-
Light-year is distance, not time.
10. A
-
A galaxy 2.5 × 10⁶ light-years away means its light takes 2.5 × 10⁶ years to reach Earth.
-
It does not mean the galaxy is that age.
11. B
-
Light takes time to travel.
-
If a galaxy is 100 million light-years away, we see it as it was 100 million years ago.
-
Telescopes are basically time machines, but with less drama.
12. A
-
Astronomical distances are extremely large.
-
Light-years make these distances easier to express than metres or kilometres.
13. A
-
Correct increasing size scale:
-
Earth
-
Solar System
-
Milky Way
-
Universe
-
14. C
-
Another star in our galaxy is outside the Solar System but inside the Milky Way.
-
Mars, the Moon and artificial satellites are inside or linked to the Solar System.
15. A
-
Stars produce energy by nuclear fusion.
-
Planets reflect light.
-
Stars are not planets.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
16. A
-
In a main sequence star like the Sun, hydrogen nuclei fuse to form helium.
-
This releases energy.
17. A
-
During fusion, some mass is converted into energy.
-
This is why stars can release huge amounts of energy.
-
The equation idea behind it is:
-
E = mc²
-
18. B
-
Fusion needs:
-
very high temperature
-
very high pressure
-
-
These conditions allow nuclei to overcome electrostatic repulsion.
19. A
-
A stable main sequence star is in equilibrium.
-
Inward gravitational force is balanced by outward pressure from fusion/radiation.
-
This balance keeps the star stable for most of its life.
20. B
-
The Sun’s energy comes mainly from nuclear fusion in its core.
-
It is not ordinary chemical burning.
21. B
-
A star forms from a nebula.
-
A nebula is a cloud of gas and dust.
22. B
-
Gravity pulls particles in the nebula together.
-
This collapse can begin star formation.
23. B
-
As the cloud collapses, gravitational potential energy is transferred to internal/thermal energy.
-
Temperature increases.
-
Eventually, conditions may become hot enough for fusion.
24. A
-
A protostar becomes a main sequence star when hydrogen fusion begins steadily in the core.
-
This is when the star becomes stable.
25. A
-
Correct early sequence:
-
nebula
-
protostar
-
main sequence star
-
26. B
-
A star spends most of its lifetime as a main sequence star.
-
This is the long stable stage where hydrogen fusion occurs.
27. A
-
A Sun-like star runs low on hydrogen in its core.
-
It expands and becomes a red giant.
28. C
-
A star similar in mass to the Sun eventually becomes a white dwarf.
-
It does not have enough mass to become a black hole.
29. A
-
Sun-like star sequence:
-
nebula
-
protostar
-
main sequence
-
red giant
-
white dwarf
-
30. A
-
A very massive star becomes a red supergiant after the main sequence stage.
-
It may later explode as a supernova.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
31. B
-
A very massive star may end as:
-
neutron star
-
black hole
-
-
The final result depends on the mass of the remaining core.
32. A
-
Massive stars can die in a supernova explosion.
-
This is a huge release of energy.
33. A
-
Massive star sequence:
-
nebula
-
protostar
-
main sequence
-
red supergiant
-
supernova
-
neutron star or black hole
-
34. A
-
A black hole is a region where gravity is so strong that not even light can escape.
-
This happens if the collapsed core is extremely massive.
35. B
-
Light cannot escape from inside the event horizon.
-
So black holes are difficult to observe directly.
-
They can be detected by effects on nearby matter and light.
36. A
-
A white dwarf is the hot dense remaining core of a low/medium mass star.
-
Sun-like stars end this way.
37. A
-
A neutron star is an extremely dense remnant made mostly of neutrons.
-
It can form after a supernova.
38. A
-
If the collapsed core after a supernova is extremely massive, it may form a black hole.
-
If less massive, it may form a neutron star.
39. A
-
Supernovae spread heavy elements into space.
-
These elements can later become part of planets and living things.
40. A
-
Heavy elements are formed and spread by supernovae.
-
These elements help form rocky planets and life-supporting materials.
-
We are literally made of star leftovers. Very premium recycling.
41. B
-
A shift towards longer wavelength is called redshift.
-
Red light has longer wavelength than blue/violet light.
42. B
-
Redshift from a distant galaxy usually means it is moving away from Earth.
-
This is similar to a Doppler effect for light.
43. A
-
Larger redshift means the galaxy is receding faster.
-
In exam physics, greater redshift usually means greater recession speed.
44. A
-
Most distant galaxies show redshift.
-
This is evidence that galaxies are moving away.
-
Therefore the Universe is expanding.
45. A
-
Cosmic microwave background radiation supports the idea that the Universe began hot and dense.
-
It is leftover radiation from the early Universe.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
46. A
-
Cosmic microwave background radiation is leftover radiation from the early Universe.
-
It is observed in all directions in space.
47. A
-
The Big Bang theory says the Universe began from a hot, dense state.
-
Since then, the Universe has been expanding and cooling.
48. A
-
Given:
-
speed = 1.2 × 10⁷ m/s
-
distance = 4.0 × 10²³ m
-
-
speed / distance:
-
1.2 × 10⁷ / 4.0 × 10²³
-
= 0.30 × 10⁻¹⁶
-
= 3.0 × 10⁻¹⁷ s⁻¹
-
49. A
-
Larger redshift usually means greater recession speed.
-
Galaxy Y has larger redshift, so it is moving away faster than X.
50. A
-
In exam physics, redshift of distant galaxies is evidence that galaxies are receding.
-
This supports the expanding Universe model.
-
“Tired light” is not the accepted explanation in this syllabus context.
For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.
Common Traps From This Chapter
| Trap | Correct Rule |
|---|---|
| Sun | star in the Milky Way |
| Galaxy | many stars, gas and dust held by gravity |
| Milky Way | galaxy containing the Solar System |
| Universe | all matter, energy, space and time |
| Light-year | distance, not time |
| 1 light-year | about 9.6 × 10¹⁵ m |
| Distant objects | seen as they were in the past |
| Star energy | nuclear fusion |
| Main sequence fusion | hydrogen to helium |
| Star equilibrium | gravity inward, pressure outward |
| Star formation | nebula → protostar → main sequence |
| Sun-like star ending | red giant → white dwarf |
| Massive star ending | red supergiant → supernova → neutron star/black hole |
| Black hole | gravity so strong light cannot escape |
| Supernova | spreads heavy elements |
| Redshift | wavelength increases |
| Galaxy redshift | moving away |
| Larger redshift | faster recession |
| Most galaxies redshifted | Universe expanding |
| CMB radiation | evidence for hot dense early Universe |
| Big Bang theory | Universe began hot/dense and expanded |