Why isn't Pluto a planet?

In 2006 the International Astronomical Union set out what makes a planet. Pluto hasn't cleared the area around its orbit, so it became a dwarf planet.

Are the numbers exact?

We only use values that barely change, and even those are asked as round figures, like about 8 minutes.

Do I get the same questions every time?

Each round is picked at random. Only a friend's challenge link gives you the same questions in the same order.

🪐 Space Quiz

There's a planet where a day is longer than a year?

Ten questions on the solar system, black holes and the first people in space, all straight out of the science textbook. Each answer comes with a one-line reason, so even your misses teach you something.

About this quiz

Planets, black holes and the first people in space, all straight out of the science textbook. Each answer comes with a one-line reason, so even your misses teach you something.

Some questions involve numbers, like how long sunlight takes to reach us, but none ask about figures that keep changing, such as how many moons a planet has. Those shift every time a new moon is found.

Questions: 10
Subject: Science
Price: Free
Sign-in: Optional
Devices: Phone, tablet, desktop

How to play

One fact per planet: Biggest Jupiter, hottest Venus, sideways Uranus. Remember one thing about each planet and most questions fall into place.
The first people in space: There are questions about people too, like the first human in space and the first to walk on the Moon. They're easy to mix up, so remember the years.
Review only what you missed: Under your result you'll find each question you missed, what you picked, the right answer and why. Finish a round and your review is done too.

Score ranks

Astronaut Selected
A perfect score. The next seat on the rocket is yours.
Observatory Regular
You know nearly all of it. Your friends have a stargazing guide now.
Made It to the Moon
Solid basics. Just remember one fact per planet you mixed up.
Still in Earth's Air
Space is hard, that's the point. Read the explanations and you'll reach orbit next try.

Frequently asked questions

Why isn't Pluto a planet?: In 2006 the International Astronomical Union set out what makes a planet. Pluto hasn't cleared the area around its orbit, so it became a dwarf planet.
Are the numbers exact?: We only use values that barely change, and even those are asked as round figures, like about 8 minutes.
Do I get the same questions every time?: Each round is picked at random. Only a friend's challenge link gives you the same questions in the same order.