Astronomy & Space · Unit 11

Galaxies

The Milky Way, galaxy types, structure and clusters

For most of history the Milky Way was assumed to be everything there was. That the faint smudges were other galaxies at enormous distance was only settled in the 1920s.

The unit covers the Milky Way's structure and our position in it, galaxy types, clusters and the cosmic web, and active galaxies and quasars powered by supermassive black holes.

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

Types of Galaxies
Galaxy Structure
The Milky Way
Clusters and the Cosmic Web
Active Galaxies and Quasars

Where this fits

Follows The Lives of Stars. Leads into Cosmology.

Where people slip

We cannot see the Milky Way from outside, so its shape is inferred from measurements taken inside it. Every picture of our own galaxy is an artist's reconstruction.

How the unit is structured

Galaxies 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.

Active Galaxies and Quasars

Build the sentenceLevel 3
1. Build a true sentence about what powers a quasar.
Answer: A quasar is powered by a black hole
A quasar shines because matter heats up as it falls toward a supermassive black hole in a galaxy's core.
Fact or fibLevel 3
2. A quasar is a dim, faint object that is hard to detect.
Answer: False
Quasars are among the most luminous objects in the universe, outshining entire galaxies.
Fill the blankLevel 3
3. A galaxy with an unusually bright, energetic core is called an ____ galaxy.
- activecorrect
- empty
- elliptical
- average
Active galaxies have cores that blaze with energy from matter falling into a central supermassive black hole.
Match the pairsLevel 3
4. Match each active galaxy term to its meaning.
Answer: Quasar = Ultra-bright distant core; Relativistic jet = Beam of fast particles; Seyfert galaxy = Active spiral galaxy
Quasars are ultra-bright cores, jets are particle beams, and Seyfert galaxies are spirals with active centers.
Multiple choiceLevel 3
5. What powers the extremely bright center of an active galaxy?
- A supermassive black holecorrect
- A single giant star
- A cluster of comets
- A supernova explosion
Active galaxies shine from matter heating up as it falls toward a supermassive black hole in their core.
Choose all that applyLevel 4
6. Which statements describe quasars? (Choose all that apply.)
- They are extremely luminouscorrect
- They are powered by supermassive black holescorrect
- They are seen at great distancescorrect
- They are cool and dim
Quasars are ultra-bright, distant galactic cores powered by feeding supermassive black holes.

Clusters and the Cosmic Web

Build the sentenceLevel 3
7. Build a true sentence about our nearest large neighbor.
Answer: Andromeda is the nearest large galaxy to us
Andromeda is the closest large galaxy to the Milky Way, about 2.5 million light-years away.
Fact or fibLevel 3
8. The Andromeda Galaxy is moving toward the Milky Way.
Answer: True
Andromeda is approaching us and is expected to merge with the Milky Way in a few billion years.
Fill the blankLevel 3
9. The Milky Way and Andromeda both belong to a small cluster called the ____ Group.
- Localcorrect
- Virgo
- Solar
- Orion
The Local Group is the cluster of galaxies, dozens in all, that includes the Milky Way and Andromeda.
Choose all that applyLevel 4
10. Which of these galaxies belong to the Local Group? (Choose all that apply.)
- The Milky Waycorrect
- The Andromeda Galaxycorrect
- The Triangulum Galaxycorrect
- The Virgo Cluster
The Milky Way, Andromeda, and Triangulum are Local Group members; the Virgo Cluster is a separate cluster.
Guess the numberLevel 4
11. About how many million light-years away is the Andromeda Galaxy?
Answer: 2.5 million light-years
Andromeda is about 2.5 million light-years away, the nearest large galaxy to the Milky Way.
Match the pairsLevel 4
12. Match each cosmic structure to its description.
Answer: Local Group = Contains the Milky Way; Virgo Cluster = Nearest large cluster; Laniakea = Our home supercluster
The Local Group holds our galaxy, the Virgo Cluster is the nearest big cluster, and Laniakea is our supercluster.

Galaxy Structure

Choose all that applyLevel 3
13. Which of these are found in a galaxy's halo? (Choose all that apply.)
- Globular clusterscorrect
- Old starscorrect
- Dark mattercorrect
- Bright spiral arms
The halo holds globular clusters, old stars, and dark matter; spiral arms sit in the disk instead.
Fact or fibLevel 3
14. The spiral arms of a galaxy are active regions where new stars are born.
Answer: True
Spiral arms are rich in gas and dust, so they glow with bright, newly formed young stars.
Fill the blankLevel 3
15. The flat, rotating region of a spiral galaxy where the arms lie is called the ____.
- diskcorrect
- halo
- bulge
- core
The disk is the thin, spinning plane of a spiral galaxy that contains the spiral arms, gas, and dust.
Multiple choiceLevel 3
16. What is the dense ball of stars at the center of a spiral galaxy called?
- The bulgecorrect
- The halo
- The disk
- A spiral arm
The central bulge is a rounded, densely packed group of mostly older stars at a spiral galaxy's core.
Odd one outLevel 3
17. Which of these is NOT a part of a spiral galaxy?
- A cratercorrect
- The bulge
- The disk
- The halo
Bulge, disk, and halo are parts of a galaxy; craters are dents on the surfaces of moons and planets.
Build the sentenceLevel 4
18. Build a true sentence about a galaxy's hidden mass.
Answer: Dark matter surrounds galaxies in a huge halo
Each galaxy is wrapped in a large halo of dark matter whose gravity shapes how it spins.

The Milky Way

Build the sentenceLevel 3
19. Build a true sentence about our galaxy's shape.
Answer: The Milky Way is a barred spiral galaxy
The Milky Way is classified as a barred spiral galaxy because of the bar of stars through its center.
Choose all that applyLevel 3
20. Which of these are true of the Milky Way? (Choose all that apply.)
- It is a barred spiralcorrect
- It has a central supermassive black holecorrect
- It contains billions of starscorrect
- It has only about 100 stars
The Milky Way is a barred spiral with a central black hole and hundreds of billions of stars.
Fact or fibLevel 3
21. The Milky Way is shaped like a flat disk with a bulge at its center.
Answer: True
Our galaxy is a flattened spinning disk of stars with a rounded central bulge.
Fill the blankLevel 3
22. The Sun lies in the ____ Arm of the Milky Way.
- Orioncorrect
- Perseus
- Sagittarius
- Centaurus
The Sun sits in the Orion Arm, a minor spiral arm, about 27,000 light-years from the center.
Guess the numberLevel 3
23. About how many thousand light-years across is the Milky Way's disk?
Answer: 100 thousand light-years
The Milky Way's disk is roughly 100,000 light-years wide, so about 100 thousand light-years across.
Match the pairsLevel 3
24. Match each Milky Way feature to its description.
Answer: Sagittarius A* = Central black hole; Orion Arm = Where the Sun lives; Halo = Home of globular clusters
Sagittarius A* is the central black hole, the Sun sits in the Orion Arm, and the halo holds globular clusters.

Types of Galaxies

Choose all that applyLevel 3
25. Which of these are real types of galaxies? (Choose all that apply.)
- Spiralcorrect
- Ellipticalcorrect
- Irregularcorrect
- Comet
Spiral, elliptical, and irregular are all galaxy shapes; a comet is not a galaxy.
Fill the blankLevel 3
26. A spiral galaxy with a straight bar of stars crossing its center is called a ____ spiral.
- barredcorrect
- elliptical
- ringed
- lenticular
A barred spiral has a bar-shaped band of stars through the middle, with arms trailing from the bar's ends.
Match the pairsLevel 3
27. Match each galaxy to its type.
Answer: Milky Way = Barred spiral; M87 = Elliptical; Large Magellanic Cloud = Irregular
The Milky Way is a barred spiral, M87 is elliptical, and the Large Magellanic Cloud is irregular.
Multiple choiceLevel 3
28. A galaxy shaped like a smooth ball or egg, made mostly of old stars, is which type?
- Ellipticalcorrect
- Spiral
- Barred spiral
- Irregular
Elliptical galaxies are rounded, smooth collections of mostly old stars with little gas or dust.
Odd one outLevel 3
29. Which of these is NOT a type of galaxy?
- A cometcorrect
- Spiral
- Elliptical
- Irregular
Spiral, elliptical, and irregular are galaxy types; a comet is a small icy body in a solar system.
Build the sentenceLevel 4
30. Build a true sentence about how galaxies are classified.
Answer: Hubble arranged galaxies on a tuning fork diagram
Edwin Hubble sorted galaxies by shape along a tuning fork diagram of ellipticals and spirals.

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 Galaxies

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

Play this unit

Read about Galaxies

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

What Is the Milky Way? Our Home Galaxy Seen From the InsideThe Milky Way is the galaxy the Sun belongs to, a disc of a few hundred billion stars. What it is made of, where we sit in it, and how its shape was mapped.September 14, 2026 · 5 min read

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