☀️ Our Solar System
Our solar system is a huge region of space held together by the Sun's gravity. It includes eight planets, at least five dwarf planets, hundreds of moons, millions of asteroids, and billions of comets — all orbiting a single star: our Sun.
The Sun makes up about 99.8% of all the mass in the entire solar system. Its powerful gravity keeps everything — from tiny dust particles to giant Jupiter — locked in orbit around it.
🌟 The Sun
The Sun is a medium-sized star made mostly of hydrogen and helium gas. Deep inside its core, hydrogen atoms slam together in a process called nuclear fusion, creating the heat and light that make life on Earth possible. The Sun's surface temperature is about 5,500°C (10,000°F), and its core reaches an incredible 15 million°C!
🪨 Inner Planets (Rocky)
The four planets closest to the Sun — Mercury, Venus, Earth, and Mars — are called the terrestrial planets. They're made mostly of rock and metal, and they're relatively small compared to the outer planets. They all have solid surfaces you could (theoretically) stand on.
🌀 Outer Planets (Gas & Ice Giants)
Beyond Mars lie the four giant planets: Jupiter, Saturn, Uranus, and Neptune. Jupiter and Saturn are gas giants — enormous balls of hydrogen and helium with no solid surface. Uranus and Neptune are ice giants — smaller but made of heavier elements like water, ammonia, and methane ices.
🌍 Solar System in Motion
Watch the planets orbit the Sun — click any planet to learn more!
🪐 Meet the Planets
Click any planet below to see its vital statistics — size, temperature, distance from the Sun, gravity, how much you'd weigh there, and a fun fact!
📏 How Big? How Far?
The solar system is so enormous that it's almost impossible to picture. The distances between planets are mind-bogglingly vast, and the size differences are just as extreme. Let's try to make sense of it.
🔴 Sun vs. Earth — True Relative Size
The Sun's diameter is about 1.39 million km — that's roughly 109 times wider than Earth. You could line up 109 Earths across the face of the Sun, and you could fit about 1.3 million Earths inside it!
In the image above, both the Sun and Earth are shown at their true relative size. Notice how Earth is barely a speck compared to our star!
🎾 If the Sun Were a Tennis Ball…
One of the best ways to understand solar system distances is to shrink everything down. If the Sun were the size of a tennis ball (about 6.7 cm / 2.6 inches across), here's where you'd find each planet and how big they'd be:
🚗 Driving to the Planets
Here's another way to think about it: if you could drive a car at highway speed (100 km/h or about 60 mph) straight to each planet without stopping, how long would it take?
☀️ Sun: About 171 years
♂️ Mars (closest approach): About 63 years
♃ Jupiter: About 890 years
♄ Saturn: About 1,633 years
♆ Neptune: About 5,140 years — you'd need to have started driving around the time the Egyptian pyramids were being built!
☄️ Other Objects in Our Solar System
Planets aren't the only things orbiting the Sun. Our solar system is full of smaller but fascinating objects.
Comets
Frozen "dirty snowballs" of ice, dust, and rock. When they get close to the Sun, they heat up and develop a bright glowing tail that can stretch millions of miles.
Asteroids
Rocky leftovers from the solar system's formation 4.6 billion years ago. Most orbit in the Asteroid Belt between Mars and Jupiter.
Dwarf Planets
Objects like Pluto, Eris, Ceres, Haumea, and Makemake that orbit the Sun and are round, but haven't cleared their orbit of other debris.
Kuiper Belt
A vast ring of icy bodies beyond Neptune's orbit. It's home to Pluto and stretches from about 30 to 50 AU from the Sun.
Oort Cloud
A giant shell of icy objects at the very edge of the Sun's influence — up to 100,000 AU away. It's where long-period comets come from.
Moons
Natural satellites that orbit planets. There are over 200 known moons in our solar system. Jupiter alone has 95! Earth has just one: our Moon.
🌙 Our Moon
Earth's Moon is the fifth-largest moon in the solar system and the only place beyond Earth where humans have walked. It's been our constant companion in space, and it plays a huge role in life on Earth.
📊 Moon Quick Facts
Diameter
3,475 km (2,159 miles) — about ¼ the width of Earth, or roughly the distance from New York to Los Angeles.
Distance
384,400 km (238,855 miles) from Earth on average. You could fit about 30 Earths in the gap between us!
Gravity
1.62 m/s² (0.17 g) — about 1/6 of Earth's gravity. If you weigh 100 lbs on Earth, you'd weigh just 17 lbs on the Moon!
Temperature
Ranges from -173°C to 127°C (-280°F to 260°F). With no atmosphere to trap heat, the difference between day and night is extreme.
🌕 Why Is the Moon So Important?
The Moon does much more than light up the night sky. Its gravitational pull creates tides in Earth's oceans — the regular rise and fall of sea levels that affect coastlines, marine life, and even navigation. The Moon also helps stabilize Earth's tilt, which keeps our seasons relatively consistent. Without the Moon, Earth's axis could wobble wildly, causing extreme climate swings.
The Moon also slows down Earth's rotation. The Moon's gravity has been gradually making our days longer over time, and it's still happening — days get about 2.3 milliseconds longer every century.
🌗 Phases of the Moon
The Moon doesn't produce its own light — it reflects sunlight. As the Moon orbits Earth (once every 27.3 days), we see different amounts of its sunlit side, creating the lunar phases: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, and Waning Crescent. The complete cycle takes about 29.5 days, which is where the word "month" comes from!
👨🚀 Humans on the Moon
On July 20, 1969, NASA astronauts Neil Armstrong and Buzz Aldrin became the first humans to walk on the Moon during the Apollo 11 mission, while Michael Collins orbited above. Armstrong's famous words — "That's one small step for man, one giant leap for mankind" — were heard by an estimated 600 million people watching on TV.
Between 1969 and 1972, a total of 12 astronauts walked on the Moon across six Apollo missions. They brought back 382 kg (842 lbs) of moon rocks, set up scientific experiments, and even drove a lunar rover! NASA's Artemis program aims to return astronauts to the Moon, including the first woman and first person of color to walk on its surface.
🔭 How Did the Moon Form?
Most scientists believe the Moon formed a very long time ago when a Mars-sized object called Theia slammed into the young Earth. The collision blasted an enormous amount of debris into orbit, which eventually clumped together to form the Moon. This is called the Giant Impact Hypothesis, and it explains why the Moon's composition is so similar to Earth's outer layers.
🌍 Other Interesting Moons
Earth's Moon isn't the only fascinating moon in our solar system! Here are a few standouts:
Io (Jupiter)
The most volcanically active body in the solar system, with hundreds of volcanoes and lava lakes covering its surface.
Europa (Jupiter)
Has a smooth icy surface covering a vast saltwater ocean underneath. Scientists think it's one of the best places to look for alien life!
Titan (Saturn)
The only moon with a thick atmosphere and liquid lakes on its surface — though the lakes are made of methane and ethane, not water.
Enceladus (Saturn)
Shoots giant geysers of water ice into space from its south pole. Like Europa, it has a subsurface ocean that could support life.
💜 The Story of Pluto
For 76 years, Pluto was considered the ninth planet. But in 2006, scientists made a tough decision that changed the solar system as we knew it. Here's the full story.
📅 A Timeline of Discovery
📋 What Makes a Planet?
In 2006, the IAU said a planet must meet three criteria:
Pluto meets the first two rules but fails the third. Its orbit is crowded with other Kuiper Belt objects. That's why it was reclassified as a dwarf planet — still fascinating, just in a different category.
Even though Pluto lost its planet status, the New Horizons mission showed us that it's one of the most amazing worlds in our solar system — with towering ice mountains, nitrogen glaciers, and a hazy blue atmosphere. Dwarf planet or not, Pluto is pretty incredible!
🧩 Planet Ordering Challenge
Drag the planets from the bank and drop them in the correct order from the Sun. Can you get all 8 right?