Astronomy & Space · Unit 10

The Lives of Stars

Star birth, main sequence, red giants, supernovae and remnants

A star is a balance between gravity pulling in and fusion pushing out, and its entire life story is the record of that balance shifting.

The unit follows stars from formation in gas clouds through the main sequence, into red giants, and out through the endings - white dwarfs, supernovae, neutron stars and black holes - which depend almost entirely on the star's mass.

This unit breaks down into 21 short steps and 120 questions, starting at difficulty 3 and building to 4. Below you can see exactly what it covers, how the path is structured, and worked examples with explanations.

Steps: 21
Questions: 120
Difficulty: 3-4

What this unit covers

Supernovae
White Dwarfs, Neutron Stars, Black Holes
Red Giants and Old Age
Main Sequence Life
How Stars Are Born

Where this fits

Needs The Sun and Stars. Leads into Galaxies and into Relativity and Black Holes.

Where people slip

More massive stars live shorter lives, not longer. They have more fuel and burn it disproportionately faster, so the biggest stars last a few million years while small ones outlive the current age of the universe.

How the unit is structured

The Lives of Stars runs as 21 short steps that unlock in order. 15 are practice rounds and 6 are challenge rounds that pull together everything before them. Questions start at difficulty 3 and climb to 4 as you progress.

Step 1 · easierStep 21 · harder

Challenge rounds

Example questions

30 real questions from this unit, with the answer and the reason behind it, grouped by what they practise. There are 120 in the unit altogether.

How Stars Are Born

Build the sentenceLevel 3
1. Build a true sentence about where stars come from.
Answer: Stars are born inside clouds of gas
New stars form inside cold clouds of gas and dust in space.
Choose all that applyLevel 3
2. Which of these are involved in the birth of a star? (Choose all that apply)
- A cloud of gas and dustcorrect
- Gravity pulling material togethercorrect
- A hot protostar formingcorrect
- An iron core exploding
Stars form as gravity pulls gas and dust into a hot protostar, while iron cores belong to dying stars.
Fact or fibLevel 3
3. Stars are usually born one at a time, far away from any gas cloud.
Answer: False
Stars usually form in groups inside giant clouds of gas and dust, not alone in empty space.
Fill the blankLevel 3
4. Before fusion begins, a collapsing ball of gas that will become a star is called a ____.
- protostarcorrect
- white dwarf
- red giant
- pulsar
A protostar is the hot, contracting ball of gas that becomes a true star once fusion starts.
Multiple choiceLevel 3
5. What force pulls the gas in a nebula together to start forming a star?
- Gravitycorrect
- Magnetism only
- The Sun's light
- Wind from a comet
Gravity slowly pulls the gas and dust of a nebula inward until it becomes dense and hot enough to form a star.
Odd one outLevel 3
6. Which of these is NOT a place where stars are born?
- A black holecorrect
- The Orion Nebula
- A molecular cloud
- A stellar nursery
Stars are born in gas clouds and nebulae, not inside black holes.

Main Sequence Life

Build the sentenceLevel 3
7. Build a true sentence about how the Sun makes energy.
Answer: The Sun fuses hydrogen into helium
The Sun's energy comes from fusing hydrogen into helium in its core.
Fact or fibLevel 3
8. More massive stars burn through their fuel faster and live shorter lives.
Answer: True
Massive stars are hotter and use fuel much faster, so they live only millions of years instead of billions.
Fill the blankLevel 3
9. A star spends most of its life on the ____ sequence, steadily fusing hydrogen.
- maincorrect
- giant
- dwarf
- final
The main sequence is the long, stable phase where a star fuses hydrogen in its core.
Guess the numberLevel 3
10. About how old is the Sun, in billions of years?
Answer: 4.6 billion years
The Sun is about 4.6 billion years old, roughly halfway through its life.
Multiple choiceLevel 3
11. During its main sequence life, what does a star fuse in its core?
- Hydrogen into heliumcorrect
- Helium into hydrogen
- Carbon into oxygen
- Iron into gold
On the main sequence a star steadily fuses hydrogen into helium, releasing the energy that makes it shine.
Odd one outLevel 4
12. Which of these is NOT a main sequence star?
- Betelgeusecorrect
- The Sun
- Sirius A
- Proxima Centauri
Betelgeuse is a red supergiant past the main sequence, while the others fuse hydrogen on it.

Red Giants and Old Age

Build the sentenceLevel 3
13. Build a true sentence describing a red giant.
Answer: A red giant is cooler but bigger
A red giant has a cooler surface but a much larger size than before.
Fill the blankLevel 3
14. When its core hydrogen is gone, a Sun-like star swells into a ____.
- red giantcorrect
- blue dwarf
- black hole
- comet
With core hydrogen used up, the star's outer layers expand and cool into a red giant.
Match the pairsLevel 3
15. Match each famous star with its stage of life.
Answer: Betelgeuse = Red supergiant; The Sun = Main sequence star; Sirius B = White dwarf
These well-known stars are each at a different stage of a star's life.
Multiple choiceLevel 3
16. What happens to a Sun-like star when the hydrogen in its core runs out?
- It swells into a red giantcorrect
- It instantly explodes as a supernova
- It turns into a planet
- It becomes brighter and bluer
When core hydrogen runs low, the outer layers expand and cool, turning the star into a red giant.
Odd one outLevel 3
17. Which of these is NOT a type of stellar remnant?
- Red giantcorrect
- White dwarf
- Neutron star
- Black hole
A red giant is a stage in a living star's life, while the others are remnants of dead stars.
Choose all that applyLevel 4
18. Which of these are true about red giants? (Choose all that apply)
- They are larger than main sequence starscorrect
- Their surfaces are cooler and reddercorrect
- Their cores have run low on hydrogencorrect
- They are the smallest stars known
Red giants are swollen, cool, and red because their cores have used up hydrogen.

Supernovae

Build the sentenceLevel 3
19. Build a true sentence about what a supernova is.
Answer: A supernova is an exploding star
A supernova is the explosion of a dying massive star.
Fill the blankLevel 3
20. Elements heavier than iron are forged in the intense heat of a ____.
- supernovacorrect
- sunrise
- comet tail
- planet
The extreme conditions of a supernova can forge heavy elements and scatter them into space.
Match the pairsLevel 3
21. Match each supernova term with what it is.
Answer: Crab Nebula = Supernova remnant; Type Ia = Exploding white dwarf; Type II = Collapsing massive star
These match supernova types and remnants to what they are.
Choose all that applyLevel 4
22. Which statements about supernovae are true? (Choose all that apply)
- They forge elements heavier than ironcorrect
- They can leave a neutron star or black holecorrect
- Type II comes from a massive star's collapsecorrect
- They occur when a red dwarf gently runs out of fuel
Supernovae come from massive stars or white dwarfs, forge heavy elements, and leave dense remnants.
Fact or fibLevel 4
23. The elements in your body heavier than hydrogen were forged inside stars and supernovae.
Answer: True
Carbon, oxygen, iron and more were made in stars and scattered by supernovae long ago.
Guess the numberLevel 4
24. A star needs to be at least about how many times the Sun's mass to end in a core-collapse supernova?
Answer: 8 solar masses
Stars above about 8 solar masses can collapse and explode as supernovae.

White Dwarfs, Neutron Stars, Black Holes

Build the sentenceLevel 3
25. Build a true sentence about black holes.
Answer: Nothing can escape a black hole
Once past the event horizon, nothing, not even light, can escape a black hole.
Choose all that applyLevel 3
26. Which of these are possible remnants left after a star dies? (Choose all that apply)
- White dwarfcorrect
- Neutron starcorrect
- Black holecorrect
- A brand-new protostar
Dying stars can leave white dwarfs, neutron stars, or black holes, depending on their mass.
Fact or fibLevel 3
27. A neutron star is incredibly dense, packing more mass than the Sun into a city-sized ball.
Answer: True
A neutron star squeezes more than the Sun's mass into a sphere only about 20 km across.
Fill the blankLevel 3
28. A rapidly spinning neutron star that beams radio pulses is called a ____.
- pulsarcorrect
- quasar
- white dwarf
- nebula
A pulsar is a spinning neutron star whose beams sweep past us like a lighthouse.
Match the pairsLevel 3
29. Match each stellar remnant with the star or fate that made it.
Answer: White dwarf = Sun-like star's remnant; Neutron star = Massive star's dense core; Black hole = Nothing escapes it
Each remnant matches the kind of star and fate that produced it.
Multiple choiceLevel 3
30. What is left behind after a Sun-like star gently ends its life?
- A white dwarfcorrect
- A black hole
- A brand-new nebula that never fades
- A gas giant planet
A Sun-like star sheds its outer layers and leaves a hot, dense core called a white dwarf.

Where these questions come from. Each unit starts as a plan of the concepts it should cover and the difficulty it should span. Questions are written against that plan with AI assistance, then checked by a validator that rejects anything without a single defensible answer, an explanation, or plausible wrong options. How we write questions sets out the whole process, and corrections are fixed in the bank and reach the site and the app the same day.

How you practise

This unit mixes 14 different question formats, so you are recalling and applying rather than recognising the same layout every time.

Build the sentence
Choose all that apply
Fact or fib
Fill the blank
Guess the number
Match the pairs
Multiple choice
Odd one out
Picture question
Put in order
Sort into groups
Spell it
True or false
Type the answer

Practise The Lives of Stars

120 questions across 21 steps. Start with step one and crawl at your own pace.

Play this unit

Read about The Lives of Stars

Explainers from our blog on what this unit covers. Each one ends with real questions from the bank.

What Is a Neutron Star? A Sun Squeezed Into a CityA neutron star packs more than the Sun's mass into a ball twenty kilometres across. How it forms, what its matter is like.September 14, 2026 · 4 min read

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