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🪐 KNOW PRIMARY · AGES 6–11

PLANETS &
ASTRONOMY

🪐 From Tiny Rocks to Massive Giants — Our Solar System!

📖 8 Planets 🆓 FREE + PRO ⏱️ 5 min per comic 🧠 Quiz included
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NEBULA
4.5 billion years ago
→
☀️
SUN FORMS
First light
→
🪨
DUST CLUMPS
Accretion disk
→
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PLANETS FORM
Gravity wins
🌌 HOW THE SOLAR SYSTEM FORMED
TOPIC 07 · PLANETS & ASTRONOMY · NEBULA · 4.5 BILLION YEARS AGO
PAGE 1 OF 5 — THE NEBULA CLOUD
BEGINNING
A colorful nebula cloud of gas and dust slowly rotating in deep space 4.5 billion years ago
4.5 BILLION YEARS AGO
In the vast darkness of space, a giant cloud of gas and dust slowly rotated. This nebula was enormous — many light-years across! Gravity pulled everything inward, and the spinning increased. The cloud heated up as it compressed. This is how our solar system began!
COLLAPSING!
NEBULA
A giant cloud of gas and cosmic dust spreading across light-years of dark space
💫 Giant cloud of gas
🌀 And cosmic dust
GRAVITY
Gravity pulling the nebula cloud inward from all directions toward the center
📍 Invisible force pulling
↪️ Everything toward center
PAGE 2 OF 5 — THE SUN IS BORN
IGNITION
The center of a collapsing nebula igniting in nuclear fusion as the Sun blazes to life
THE CENTER IGNITES
As the nebula collapsed, the center became unbelievably hot and dense. Gravity compressed hydrogen so powerfully that nuclear fusion began. The Sun was born! It blazed to life at the heart of the collapsing cloud. Hydrogen became helium, releasing incredible energy. Our star was alive!
BURNING!
FUSION
Nuclear fusion in the forming Sun: hydrogen atoms merging into helium releasing incredible energy
🔥 Hydrogen merges into helium
💥 Nuclear reaction releases energy
ENERGY
The newborn Sun shining for the first time, radiating light and heat outward
☀️ Powerful radiation outward
🌟 Sun shines for first time ever
DISK
The protoplanetary disk of gas and dust still spinning around the newborn young Sun
🌀 Dust and gas still spinning
↪️ Around the newborn star
PAGE 3 OF 5 — THE ACCRETION DISK
DUST GRAINS
Dust grains orbiting the young Sun in a flat spinning disk around the newborn star
💨 Particles orbiting Sun
🌀 In a flat spinning disk
COLLISIONS
Dust grains colliding and sticking together to form kilometer-sized chunks called planetesimals
💥 Dust grains stick together
⚪ Forming larger clumps
ACCRETION
The protoplanetary accretion disk: a flat spinning cloud of dust building the planets around the Sun
THE DISK
The remaining disk of dust and gas orbited the young Sun. Tiny particles crashed together, sticking and forming larger objects. Planetesimals! These were kilometer-sized chunks of rock and ice. They collided and merged, creating bigger and bigger bodies. Gravity helped them grow. Planetary building had begun!
SWIRLING!
PAGE 4 OF 5 — PLANETS ASSEMBLE
ASSEMBLY
Planets forming from the accretion disk: rocky planets in the hot inner zone, gas giants in the cold outer zone
PLANETS FORM
Planetesimals collided and merged in a chaotic dance. Gradually, larger planets formed! Closer to the Sun, rocky planets collected. Further out, cold gas giants grew massive by capturing hydrogen and helium. The inner solar system became hotter; the outer system stayed cold. Each zone created different types of planets!
GROWING!
HOT ZONE
The hot inner zone forming rocky planets: Mercury, Venus, Earth, and Mars close to the Sun
🔥 Rocky planets near Sun
🪨 Mercury, Venus, Earth, Mars
ASTEROID BELT
The asteroid belt between Mars and Jupiter shaped by Jupiter's powerful gravitational influence
🪨 Belt of asteroids
⭐ Jupiter's gravity shaped it
COLD ZONE
The cold outer zone forming gas giants: Jupiter, Saturn, Uranus, and Neptune far from the Sun
❄️ Gas giants far out
🌀 Jupiter, Saturn, Uranus, Neptune
PAGE 5 OF 5 — OUR SOLAR SYSTEM TODAY
PRESENT
The completed solar system: 8 planets in stable orbits around the Sun after millions of years of formation
TODAY: A STABLE SYSTEM
After millions of years of chaos, our solar system settled into a stable configuration. Eight planets orbit the Sun in predictable paths. Moons orbit planets. Asteroids and comets exist in distant zones. The Sun will burn hydrogen for billions of years more. In about 5 billion years, it will expand and engulf the inner planets. But for now, our cosmic home is stable and wonderful!
STABLE!
PLANETS
🌟 THE EIGHT PLANETS
Mercury, Venus, Earth, Mars orbiting close. Jupiter, Saturn, Uranus, Neptune far away. All born from the same nebula cloud 4.5 billion years ago!
☀️ Sun at center
🌍 Stable orbits
💫 Perfect distance from star
🪐 Made from same dust cloud
FUTURE
The far future: the Sun will expand into a red giant in about 5 billion years, swallowing the inner planets
⏰ 5 billion years from now
💥 Sun will expand as a red giant
🧠 QUIZ TIME!
HOW THE SOLAR SYSTEM FORMED · 5 QUESTIONS
QUESTION 01
What was the solar system's starting point?
QUESTION 02
How did the Sun form?
QUESTION 03
What are planetesimals?
QUESTION 04
Why are rocky planets near the Sun and gas giants far away?
QUESTION 05
When did the solar system form?
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