🌙 Look Up
Before you learn anything new, activate what you already know. This makes new information stick much more effectively.
🌟 The Starter Question
On a clear night, away from city lights, how many individual stars do you think you can see with the naked eye? Scientists estimate it's somewhere between 2,500 and 5,000 — but they're all in just our own galaxy. There are estimated to be 2 trillion galaxies in the observable Universe.
Think about what you can see in the night sky. Use these picture prompts:
When I look at the night sky I can see _______________.
I know that the Moon is _______________.
The Sun is different from the Moon because _______________.
The Moon appears bright in the night sky. Why can we see the Moon?
🛰️ Satellites
A satellite is any object that orbits another object.
🌕 Natural Satellite
An object that orbits another naturally — formed by nature. Example: the Moon orbits Earth. The Moon is kept in orbit by Earth's gravity and its own sideways motion.
💡 Many planets have natural satellites — Jupiter has over 90 moons!
🛸 Artificial Satellite
An object made by humans and put into orbit. Examples include GPS satellites, weather satellites, and the International Space Station (ISS).
💡 The ISS is visible to the naked eye — light reflected from it reaches us in a fraction of a second.
🌍 Why Don't Satellites Fall Down?
A satellite is constantly falling towards Earth due to gravity — but it's also moving sideways so fast that it keeps "missing" Earth. This sideways motion + gravity = orbit. Think of it like swinging a ball on a string: the string is gravity.
Match the Satellite Types
Click a blue term then the correct white description to match them up.
🪐 Our Solar System
Our Solar System contains the Sun, eight planets, their moons, dwarf planets, asteroids, and comets — all held together by the Sun's gravity.
The Eight Planets — In Order
🧠 Memory Trick
Use a mnemonic to remember the planets in order from the Sun. One classic is:
"My Very Educated Mother Just Served Us Nachos"
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
| # | Planet | Type | Approx. distance from Sun | Interesting fact |
|---|---|---|---|---|
| 1 | ☿ Mercury | Rocky | 58 million km | No atmosphere — extreme temperature swings |
| 2 | ♀ Venus | Rocky | 108 million km | Hottest planet — thick CO₂ atmosphere traps heat |
| 3 | 🌍 Earth | Rocky | 150 million km | Only known planet with life |
| 4 | ♂ Mars | Rocky | 228 million km | Has the largest volcano in the Solar System |
| ⭐ ASTEROID BELT — between rocky inner planets and gas giants ⭐ | ||||
| 5 | ♃ Jupiter | Gas Giant | 778 million km | Largest planet — the Great Red Spot is a storm bigger than Earth |
| 6 | ♄ Saturn | Gas Giant | 1.4 billion km | Famous rings made of ice and rock; could float on water! |
| 7 | ♅ Uranus | Ice Giant | 2.9 billion km | Rotates on its side — nearly 90° tilt |
| 8 | ♆ Neptune | Ice Giant | 4.5 billion km | Strongest winds in the Solar System — up to 2,100 km/h |
🔴 Wait — What About Pluto?
Pluto was classified as the 9th planet until 2006. The International Astronomical Union then defined a "planet" as an object that: (1) orbits the Sun, (2) has enough mass to be roughly spherical, and (3) has cleared its orbital neighbourhood of other debris. Pluto fails condition 3 — it shares its orbit with other Kuiper Belt objects — so it was reclassified as a dwarf planet.
Venus is closer to the Sun than Earth, but Mercury is even closer. Yet Venus is hotter than Mercury. What best explains this?
Years and Orbits
📅 What is a Year?
A year is the time it takes for a planet to complete one orbit around the Sun. The further a planet is from the Sun, the longer its orbit path AND the slower its orbital speed — so years get much longer.
Earth: 365 days | Mercury: 88 days | Neptune: 165 Earth years
☄️ Comets & Meteors
☄️ Comets
Comets are balls of ice and dust that orbit the Sun in long, stretched elliptical orbits. When a comet comes close to the Sun:
- The Sun heats the ice → it turns to gas
- This gas and dust is blown back by solar wind
- This creates the comet's glowing tail
- The tail always points away from the Sun
Example: Halley's Comet passes Earth every ~76 years. It will return in 2061.
🌠 Meteors & Meteorites
As Earth moves through space, it collides with small lumps of material (rock, metal, dust):
- Meteor — burns up in Earth's atmosphere creating a streak of light ("shooting star"). The friction with air causes it to glow.
- Meteorite — a larger meteor that does NOT fully burn up and hits Earth's surface.
💡 The Chicxulub meteorite, which hit Earth ~66 million years ago, is linked to the extinction of the dinosaurs.
🌑 Comet Structure
Nucleus: The solid centre — a "dirty snowball" of ice, rock and dust (typically 1–50 km wide).
Coma: A fuzzy cloud of gas and dust surrounding the nucleus when near the Sun.
Tail: Can stretch for millions of km. Always points away from the Sun due to solar wind pressure.
A comet is travelling around the Sun in its orbit. Where in its orbit would you expect the comet's tail to be longest and brightest?
| Feature | Comet | Meteor |
|---|---|---|
| What is it made of? | ||
| Does it orbit the Sun? | ||
| What do we see from Earth? |
🌌 Galaxy & Universe
🔭 The Scale of Everything
The Universe is almost incomprehensibly large. Scientists use light-years as a unit of distance because normal units (km, miles) are far too small to be useful. One light-year = the distance light travels in one year = about 9.5 trillion km.
Scale Explorer: Objects in the Universe
The bars below show the relative scale of different objects — hover over each to read the data.
Light Travel Times — the Language of Astronomy
⏱️ Why does distance = time for light?
Light travels at 300,000 km per second — the fastest anything in the Universe can travel. Even at this speed, the Universe is so enormous that we measure distances by how long light takes to travel them.
🌟 Fascinating: when you look at the night sky, you are looking back in time. The star you see might not even exist anymore.
| Object | Distance | Light travel time | What does this mean? |
|---|---|---|---|
| The Moon | 384,000 km | ~1.3 seconds | When you look at the Moon, you see it as it was 1.3 seconds ago |
| The Sun | 150 million km | ~8 minutes | If the Sun disappeared, we wouldn't know for 8 minutes |
| Saturn | 1.4 billion km | ~1.5 hours | Light from Venus takes ~2 minutes; from Saturn ~1.5 hours |
| Proxima Centauri (nearest star) | 40 trillion km | 4.2 years | The light you see left there 4.2 years ago |
| Andromeda Galaxy | 2.5 million light-years | 2.5 million years | Andromeda is visible to the naked eye — you're seeing it as it was 2.5 million years ago |
The Milky Way & Our Place in It
🌌 Our Galaxy
Our Solar System is part of the Milky Way galaxy — a spiral galaxy containing an estimated 100–400 billion stars. Our Sun is one ordinary star, about two-thirds of the way from the centre.
The Milky Way is ~100,000 light-years wide. It takes 230 million years for our Solar System to orbit the galactic centre once.
🌌 The Universe
The Universe contains an estimated 2 trillion galaxies. It began approximately 13.8 billion years ago in the Big Bang — and it is still expanding today.
Our nearest large galaxy is Andromeda (M31) — just about visible to the naked eye as a faint smudge on a dark night.
A student says: "The Andromeda galaxy is 2.5 million light-years away. This means Andromeda is 2.5 million years old." What is wrong with this statement?
✍️ Big Questions
These questions draw on everything from this lesson. Answer from memory first — then use the reveal buttons to check.
🧠 Why Answer From Memory?
Research shows that trying to recall information — even when you're not sure — strengthens your memory far more than re-reading. This is called the testing effect. Don't look back at the lesson first!
Q1. What is a satellite? Give one example of a natural and one example of an artificial satellite. [3 marks]
Natural example: the Moon (orbits Earth). (1)
Artificial example: the International Space Station / GPS satellite / weather satellite. (1)
Q2. Write the eight planets in order from the Sun. [2 marks]
Q3. What is the difference between a meteor and a meteorite? [2 marks]
Q4. Explain why planets and moons are visible in the night sky, even though they do not produce their own light. [2 marks]
Q5. ⭐ Extended Writing (6 marks)
"Compare the time it takes for light to reach us from different objects that you can see in the night sky. Use specific examples and explain what these differences in light travel time tell us about the scale of the Universe."
📐 Writing scaffold — click a sentence starter to copy it to your answer box
- The Moon is ~384,000 km away; light takes ~1.3 seconds to reach Earth (1)
- The Sun is 150 million km away; light takes ~8 minutes (1)
- Planets are at varying distances — Venus ~2 minutes, Saturn ~1.5 hours (1)
- The nearest star (Proxima Centauri) is 4.2 light-years — light takes 4.2 years to reach us (1)
- Andromeda galaxy is 2.5 million light-years away — we see it as it was 2.5 million years ago (1)
- The enormous range of light travel times (1.3 seconds to millions of years) demonstrates the vast scale of the Universe (1)
- Looking into space means looking back in time — distant objects are seen as they were in the past (1)
✅ Check & Reflect
🚦 RAG Self-Assessment — How Confident Are You?
For each learning goal, click 🔴 (not yet), 🟡 (getting there), or 🟢 (confident). Be honest — this helps you know what to revisit.
📌 What to do next
🔴 Red items: Go back to that section and re-read it, then try answering the questions again without notes.
🟡 Amber items: You almost have it — try writing a one-sentence explanation from memory.
🟢 Green items: You're confident — try teaching it to someone else, or attempt the Challenge tasks.
🪞 Reflection — I Used to Think… Now I Think
Well done — you've completed P6.1: The Night Sky!
Next lesson: P6.2 — Day and Night, Seasons & Eclipses
Remember: the best way to remember this is to come back tomorrow and try to recall it without notes.