Space is the biggest playground there is. It has a planet that rolls around the Sun on its side, dead stars squeezed down to the size of a city, and a Moon that is slowly drifting away from us. The facts below are based on what astronomers and space agencies have measured and observed, and we left out the tall tales that tend to float around online.
When you reach the end, launch into our space trivia quiz to see how many facts stuck. Curious about the science of everyday things too? Our science quiz is a great next stop.
The Sun, Our Very Own Star
- The Sun holds about 99.8% of all the mass in our solar system. All the planets, moons, asteroids and comets put together make up only a tiny leftover sliver.
- Sunlight takes about eight minutes to reach Earth. When you see the Sun, you're seeing it as it looked roughly eight minutes earlier.
- About 1.3 million Earths could fit inside the Sun. Even so, the Sun is only a medium-sized star compared with some of the giants out there.
- The Sun is actually white. It gives off every color of visible light, which mixes together into white. Earth's air scatters some blue light away, which is why it looks yellowish from the ground.
- The center of the Sun is about 15 million °C. At that heat and pressure, hydrogen atoms smash together to make helium, releasing the energy that lights and warms our planet.
- Northern and southern lights start at the Sun. Streams of charged particles from the Sun hit gases high in Earth's atmosphere and make them glow. Oxygen gives off the familiar green color.
- The Sun is about halfway through its life. It formed roughly 4.6 billion years ago, and scientists expect it to keep shining steadily for around another 5 billion years.
Planet Profiles
- A day on Venus is longer than its year. Venus takes about 243 Earth days to spin once, but only about 225 Earth days to travel around the Sun.
- On Venus, the Sun rises in the west. Venus spins in the opposite direction from most planets, so its sunrise and sunset are flipped compared with ours.
- Venus is the hottest planet, even though Mercury is closer to the Sun. Venus's thick carbon dioxide atmosphere traps heat like a heavy blanket, making the surface hot enough to melt lead.
- Mercury swings between scorching and freezing. With almost no atmosphere to hold heat, its daytime side can reach about 430 °C while its night side plunges to around −180 °C.
- Mars is red because it's rusty. Its soil and dust contain lots of iron oxide, the same stuff that makes old bikes turn orange-brown.
- Mars has the tallest volcano in the solar system. Olympus Mons rises more than twice as high as Mount Everest, and its base is about 600 kilometers across.
- Sunsets on Mars look blue. Fine Martian dust scatters light in a way that makes a blue glow around the setting Sun, the opposite of the reddish sunsets we see on Earth.
- Jupiter is more than twice as massive as all the other planets combined. It's so big that all the other planets could fit inside it.
- Jupiter has the shortest day of any planet. This giant spins once in just under 10 hours, which makes it bulge out noticeably at its middle.
- Saturn is less dense than water. If you could somehow find a bathtub big enough, the gas giant would float.
- Saturn's rings are mostly ice. The pieces range from specks smaller than sand grains to chunks as big as houses, and the main rings are amazingly thin, in many places only about 10 meters thick.
- Uranus rolls around the Sun on its side. Its axis is tipped over by about 98 degrees, possibly because something huge knocked into it long ago.
- Neptune has the fastest winds in the solar system. Its winds can whip around the planet at about 2,000 km/h, even though it is very far from the Sun's warmth.
- Neptune was found with maths before anyone saw it. In 1846, astronomers noticed Uranus wobbling in its path, calculated where an unseen planet should be, and found Neptune right near the predicted spot.
Our Neighbor, the Moon
- The Moon is slowly drifting away from Earth. Laser measurements show it moves about 3.8 centimeters farther away each year, roughly as fast as your fingernails grow.
- We always see the same side of the Moon. The Moon spins exactly once for every trip around Earth, so the same face always points toward us.
- Astronaut footprints on the Moon could last for millions of years. With no wind or rain to wipe them away, the bootprints left by Apollo astronauts should stay put for an extremely long time.
- The Moon has moonquakes. Instruments left behind by Apollo astronauts recorded the Moon's surface shaking, sometimes for many minutes at a time.
- Total solar eclipses are a cosmic coincidence. The Sun is about 400 times wider than the Moon but also about 400 times farther away, so the two look almost exactly the same size in our sky.
- The sky on the Moon is black, even in daytime. Earth's sky is blue because air scatters sunlight. The Moon has almost no air, so its sky stays dark while the Sun shines.
- The Moon was probably born from a giant crash. The leading idea is that a Mars-sized object slammed into the young Earth, and the debris thrown into space clumped together to form the Moon.
Stars, Galaxies and the Big Picture
- Looking at the stars is looking back in time. Starlight can take years, centuries or even longer to reach us, so you're seeing each star as it was when that light set off.
- The nearest star after the Sun is about 4.2 light-years away. Its name is Proxima Centauri, and its light takes more than four years to reach Earth.
- A sugar cube of neutron star would weigh about a billion metric tons. Neutron stars are the squashed cores of exploded stars, packing more mass than the Sun into a ball about the size of a city.
- A star's color reveals its temperature. Blue-white stars are the hottest and reddish stars are the coolest. Our Sun sits in between.
- Stars twinkle because of Earth's air. Moving pockets of air bend starlight back and forth. Planets usually shine more steadily because they appear as tiny discs instead of single points.
- The Milky Way contains hundreds of billions of stars. Our Sun is just one of them, sitting in one of the galaxy's spiral arms.
- The solar system takes about 230 million years to circle the galaxy. The last time Earth was in this part of its galactic orbit, the earliest dinosaurs were just appearing.
- The Andromeda Galaxy is about 2.5 million light-years away. Under dark skies it looks like a faint, fuzzy smudge, making it one of the most distant things you can see without a telescope.
- A giant black hole sits at the heart of our galaxy. Called Sagittarius A*, it has about four million times the mass of the Sun, and astronomers released the first image of it in 2022.
- You are made of star stuff. Apart from hydrogen, most atoms in your body, such as the carbon in your cells and the iron in your blood, were made inside stars long ago.
- The universe is about 13.8 billion years old. Astronomers worked this out by studying the faint glow left over from the Big Bang and how fast galaxies are moving apart.
Comets, Asteroids and Little Worlds
- Shooting stars aren't stars at all. They're streaks of light made by bits of space dust, many no bigger than a grain of sand, burning up as they zip into Earth's atmosphere.
- A comet's tail points away from the Sun. Sunlight and the solar wind push the comet's gas and dust outward, so the tail can even lead the way as a comet heads back out into space.
- Halley's Comet comes back about every 76 years. Its last visit was in 1986, and it's expected to return to the inner solar system in 2061.
- The asteroid belt is mostly empty space. Asteroids are usually so far apart that spacecraft traveling through the belt haven't needed to dodge them.
- Pluto has a giant heart. In 2015, the New Horizons spacecraft photographed a huge, bright, heart-shaped region on Pluto, and part of it is a vast plain of frozen nitrogen.
Living and Exploring in Space
- Astronauts can grow up to about 3% taller in space. Without gravity squashing them, the cushiony discs in the spine spread out. Astronauts return to their normal height after they come back to Earth.
- Flames burn in round balls in space. On Earth, hot air rises and stretches a candle flame into a teardrop. In orbit, hot air doesn't rise, so flames form spheres that often glow blue.
- Space station crews see about 16 sunrises every day. The International Space Station circles Earth roughly every 90 minutes, racing from daylight to darkness and back again.
- Space is silent. Sound needs air or another material to travel through, and space is almost completely empty, so explosions out there make no noise.
- The first animals launched into space and brought back alive were fruit flies. In 1947, scientists sent them up on a rocket to study how space radiation might affect living things.
- Two spacecraft carry a golden record about life on Earth. The Voyager probes, launched in 1977, each carry a gold-plated disc with music, natural sounds and greetings in dozens of languages.
Myths we left out
These space "facts" pop up everywhere, but they don't hold up: - Myth: The Great Wall of China is easy to see from space. Reality: The wall is long but very narrow, and astronauts report it is extremely hard, if not impossible, to spot from orbit with the naked eye. - Myth: The Moon has a "dark side" that never gets sunlight. Reality: The far side gets just as much sunlight as the near side. We simply never see it from Earth. - Myth: Summer happens when Earth is closest to the Sun. Reality: Seasons come from the tilt of Earth's axis. In fact, Earth is closest to the Sun in early January. - Myth: Astronauts float because there's no gravity in space. Reality: Gravity at the space station's height is still about 90% as strong as on the ground. Astronauts float because they are constantly falling around Earth.
Frequently asked questions
How many planets are in our solar system?
There are eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto was reclassified as a dwarf planet in 2006, but it's still a fascinating little world.
What is a light-year?
A light-year is a measure of distance, not time. It's how far light travels in one year, about 9.5 trillion kilometers.
Can I see planets without a telescope?
Yes. Mercury, Venus, Mars, Jupiter and Saturn can all be seen with the naked eye. They usually look like bright stars that don't twinkle much.
Where can I find more fun facts and trivia?
Dive into our ocean fun facts, explore the human body facts, or browse every topic on our trivia quizzes page.