There isn't an official definition of a moon, but we use the word for objects that orbit planets, dwarf planets and even asteroids. For each question, choose an answer from the three names given. You can then check your answers, and also find out a bit more about the moons.

Quiz: Moons of the Solar System

1. The biggest moon in the Solar System: (A) Titan; (B) Ganymede; (C) Callisto


2. One half of this moon is very bright and the other quite dark: (A) Europa; (B) Titania; (C) Iapetus


3. Quaoar is an unconfirmed dwarf planet – its moon is called: (A) Hi'iaka; (B) Weywot; (C) Namaka


4. The moon with a thick nitrogen atmosphere: (A) Miranda; (B) Rhea; (C) Titan


5. It has moons whose names mean “fear” and “terror”: (A) Mars; (B) Makemake; (C) Mercury


6. 243 Ida was the first asteroid found to have a moon – the moon's name is: (A) Dione; (B) Dia; (C) Dactyl


7. This moon is extremely bright because it reflects 99% of the sunlight it receives: (A) Enceladus; (B) Umbriel; (C) Oberon


8. The body with moons named for Shakespearean characters: (A) Neptune; (B) Uranus; (C) Eris


9. The most volcanically active body in the Solar System: (A) Triton; (B) Enceladus; (c) Io


10. Moons tend to take the same amount of time to rotate once as they do to orbit their planet (synchronous rotation) – a notable exception is: (A) Hyperion; (B) Metis (C) Amalthea

Answers and notes

1. The biggest moon in the Solar System: (B) Ganymede
Jupiter's moon Ganymede is about 100 km (60 mi) bigger in diameter than Saturn's moon Titan. Jupiter's Callisto is the third largest moon in the Solar System.

2. One half of this moon is very bright and the other quite dark: (C) Iapetus
In this photo we see the bright half of Saturn's Iapetus which is almost as bright as Europa. On the right hand side the beginning of the dark hemisphere is visible. Neither Jupiter's Europa nor Uranus's Titania show this striking surface patterning.

3. Quaoar is an unconfirmed dwarf planet – its moon is called: (B) Weywot
Quaoar fits the IAU (International Astronomical Union) definition of a dwarf planet, but hasn't been confirmed as one by the organization. It was named after the creator deity of the Tongva people, the original inhabitants of the Los Angeles basin. Weywot was his son. Hi'iaka and Namaka are moons of dwarf planet Haumea – they're all named after Hawaiian goddesses.

4. The moon with a thick nitrogen atmosphere: (C) Titan
Saturn's moon Titan is the only Solar System moon with a substantial atmosphere. Uranus's moon Miranda and Saturn's moon Rhea are much smaller than Titan. There is no evidence that Miranda has an atmosphere, and Rhea has only a very tenuous one.

5. It has moons whose names mean “fear” and “terror”: (A) Mars
In Greek mythology Phobos and Deimos were twin brothers who went into battle with Ares, whom the Romans called Mars. Dwarf planet Makemake's moon was discovered in April 2016. The moon has been nicknamed MK2. Mercury has no moons.

6. 243 Ida was the first asteroid found to have a moon – the moon's name is: (C) Dactyl
The mythological Dactyls lived on Mount Ida in Crete. Here is the Galileo probe image of Ida and Dactyl. Dione is Saturn's fourth largest moon. Dia is much smaller than Ida, but it's considered a moon because it orbits Jupiter.

7. A moon that's extremely bright because it reflects 99% of the sunlight it receives: (A) Enceladus
Saturn's moon Enceladus has a smooth icy surface and is one of the brightest objects in the Solar System. Umbriel and Oberon are two of Uranus's larger moons. They're both much darker than Enceladus.

8. The body with moons named for Shakespearean characters: (B) Uranus
As suggested by John Herschel, son of the discoverer of Uranus, the moons were named for literary characters, mostly Shakespearean. Neptune's moons are named for water deities. Dwarf planet Eris was named after the Greek goddess of discord. Eris's daughter Dysnomia, goddess of lawlessness, provided the name for Eris's moon.

9. The most volcanically active body in the Solar System: (C) Io
Io is alternately squeezed and stretched by the gravity of Jupiter, Callisto and Ganymede. This raises large land tides in which the surface is pulled up and down as much as 100m (330 ft). The resulting friction releases considerable heat. There is evidence of cryovolcanoes (ice volcanoes) on Neptune's Triton and Saturn's Enceladus, but they don't compare to Io which has over 400 volcanoes.

10. Moons tend to take the same amount of time to rotate as they do to orbit their planet (synchronous rotation) – a notable exception is: (A) Hyperion
Jupiter's moons Metis and Amalthea both show synchronous rotation. Saturn's moon Hyperion has such chaotic rotation that when the Cassini spacecraft did flybys, no one knew which side of the moon would be visible. This is due to Titan's gravitational effect on Hyperion.