2. Mercury is the closest planet to the sun, but it is not the hottest. Venus is the hottest planet because it has many clouds that trap in heat.
3. Venus has more volcanoes than any other planet.
4. There is only one star in our solar system - the sun.
5. Our galaxy has millions of stars.
6. Earth is the only planet people have ever walked on. Astronauts have also walked on the Earth's moon, but that's not a planet.
7. Scientists have sent robots, called rovers, to explore Mars. The rovers drive around the surface of Mars, take pictures, and send them back to Earth.
8. Mars has two small moons, named Phobos and Deimos.
9. Jupiter, the largest planet, has a “Great Red Spot.” The red spot is a huge wind storm.
10. Saturn is famous for it's bright rings, but it isn't the only planet with rings. Jupiter, Uranus, and Neptune also have them.
11. Jupiter, Saturn, Uranus, and Neptune are known as “Gas Giants” because they're made of mostly gas.
12. Uranus is the coldest planet in our solar system.
13. Neptune is the stormiest planet. Its wind storms blow three times as fast as hurricanes on Earth.
14. Pluto used to be considered a planet. Scientists decided it was too small to be a “real planet,” so it is now a dwarf planet.
15. There are five known dwarf planets in our solar system. Their names are Pluto, Ceres,Haumea,Makemake,and Eris.
16. It takes light eight minutes to travel from the sun to Earth. The sunlight you see outside right now, actually left the sun's surface eight minutes ago.
17. Pluto has three moons. Their names are Charon, Nix, and Hydra.
18. Neil Armstrong and Buzz Aldrin were the first people to walk on the moon.
19. Twelve astronauts have walked on the moon. The first astronaut walked on the moon in 1969. The last astronaut walked on the moon in 1972.
20. The sun is 93-million miles or 146-million kilometers from the earth.
21. Venus is the hottest planet.
22. Venus is the only planet which has the most volcanoes.
