Moonstruck! Trivia Quiz

About 4.5 billion years ago, the Solar System came into being from a rotating cloud of gas and dust that rotated around a newly forming star, which became the Sun. All the planets were formed from this spinning cloud and continued rotating around the Sun after they were formed. The Sun's gravity keeps the planets in these orbits.

At the same time, the planets developed their own gravitational fields so some of the dust and debris surrounding each planet formed into satellites or moons and started revolving around their closest planet.

The Earth has one moon and is called simply the Moon (always capitalised). The Moon formed in a different way to moons belonging to other planets. While there are a few theories on how it formed, the most widely accepted model is the giant-impact theory. In this theory, the Moon formed during a collision between the Earth and another small planet called Theia, about the size of the planet Mars. The debris from this impact collected in an orbit around Earth to form the Moon. This is the most accepted theory as the rocks on the Moon (brought back by astronauts) are similar to the rocks on Earth. In 2023, scientists found evidence of the remnants of Theia in the Earth's mantle (below the surface).

Earth's moon is the fifth largest moon in the solar system. It has an average diameter of 3,475 km (2,159 miles). This makes the Moon just over a quarter the width of Earth. The moon size to planet size ratio is the largest in the Solar System.

Beyond Neptune is the Kuiper belt - a region of small objects like asteroids but made of frozen volatiles such as methane, ammonia, and water. The belt is 20 times wider than the asteroid belt between Mars and Jupiter. Pluto is a dwarf planet in the Kuiper belt, though it was discovered in 1930, 21 years before the Kuiper belt. It became designated as the ninth planet of the Solar System. However, increased number of objects were being identified in the Kuiper belt including Eris in 2005. Eris is another dwarf planet much bigger than Pluto. Pluto was then re-classified as a dwarf planet. There are other dwarf planets in the Kuiper belt, but Pluto is the closest to the sun.

Pluto has five moons. Charon is by far the largest and closest to Pluto with Styx, Nix, Kerberos, and Hydra being very much smaller and distant from their planet. Charon was discovered in 1978. This caused a recalculation of Pluto's size, as it was assumed that the observed mass and reflected light were all attributable to Pluto alone but actually were Pluto and Charon combined.
Charon is 1212km (752 mi) in diameter whereas Pluto is only twice as big with a diameter of 2377km (1477 mi). The other four moons, all odd shapes, are no more than 55 km across. It is believed that the moons of Pluto formed similarly to the Earth's moon. At some stage there was a huge collision between another large object and Pluto causing five fragments to break off. These became moons as they orbited around Pluto.

Charon and Pluto actually orbit each other every 6.4 days. There is only an average of 20 000 km (12 000 mi) between Pluto and Charon.

Of the eight planets in the solar system, two do not have any moons. Mercury is one of them. Mercury does not have a noon for two reasons:

1. As it is a small planet it only has a small gravitational field. this makes it difficult to hold anything in orbit.

2. Mercury is the closest planet to the sun and the gravitational pull of the sun is really large. Any moon that tries to form around this planet would quickly be pulled away by the Sun's gravity and would disappear into the star. It is possible that Mercury did have a moon at some time, but it would not have lasted long before it was pulled away by the sun.

The asteroid belt is a ring of many solid, irregularly shaped bodies called asteroids which are much smaller than planets, and, as an average, are about one million kilometres (or six hundred and twenty thousand miles) apart. The four largest asteroids - Ceres, Vesta, Pallas, and Hygiea - make up 60% of the mass of the asteroid belt, which is estimated to be 3% that of the Moon.

Ceres is the largest of these four asteroids and meets the criteria for being called a dwarf planet. It is round and 950 km (600 miles) in diameter (The other three large asteroids are 600km (350 miles) or less in diameter). While Ceres was classified as a dwarf planet in 2006, Pluto is still 14 times more massive.

Ceres does not have a moon as, when it formed, there was not enough surrounding material left to form a moon. Also, the massive gravitational field of the giant planet Jupiter has probably interfered to disrupt any potential moon formation (and is one of the reasons why the asteroid belt has not coalesced into larger, fewer bodies).

Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan is one of 146 known moons of Saturn the sixth planet. It is Saturn's largest moon and the second largest in the solar system. It takes almost 16 days to rotate around Saturn. It is described as a planet-like moon for several reasons. It is gravitationally rounded - one of only 19 of the 300+ satellites in the Solar System to have this property.

It is twice the diameter of Earth's Moon (5,149.46 km [3,199.73 mi]) and bigger than Mercury. Not only is it unusual that this moon has an atmosphere, but it is the only moon to have an atmosphere denser than Earth's. The atmosphere is nitrogen and methane. Titan has a rocky core surrounded by layers of ice, including a crust of ice with an ammonia-infused liquid water in its subsurface layer. Its surface is smooth, indicating any craters from impacts with other large objects have been covered with ice, though there are some mountains and cryovolcanoes present.

Titan, the name, comes from the Titans, a race of pre-Olympian gods in Greek mythology

Venus is the second planet closest to the sun. It is over three-quarters of the mass of Earth so it is capable of holding onto a moon and it is believed Venus did have a moon at some point. When the solar system was being formed many more objects were flying around and collisions were inevitable.

Scientists believe there were two such collisions with Venus. The first caused a moon to be formed which initially orbited Venus. However, a second large object hit Venus causing Venus to rotate in the opposite direction (the only planet to rotate this way). This change in rotation meant its moon's orbit (now going in the opposite direction to Venus), would have caused the moon to move towards the planet until Venus' gravity ripped it apart and the debris crashed into the planet.

Uranus has 28 moons, including five major moons: Miranda, Ariel, Umbriel, Titania, and Oberon, with Titania being the largest one. Titania was discovered by William Herschel in 1787 and was named for the queen of the fairies in William Shakespeare's 16th-century play "A Midsummer Night's Dream." (All of Uranus' 28 moons are named after Shakespeare's characters or those of Alexander Pope). All of Uranus' inner moons appear to be composed of water ice and rock. The composition of the outer moons is unclear, but they are likely captured asteroids from the Kuiper belt as they are mostly irregular in shape.

Titania, like all Uranus moons, is small for a gas giant moon. While it is the largest moon of Uranus, it is only 788km (489 mi) in diameter, which is only 12% of the Moon's diameter. It orbits Uranus approximately 436,000 kilometres (271,000 mi) away in about 8.7 days.

Uranus rotates on its side. Its moons orbit around its equator. This means that all Uranus moons have extreme seasons: both northern and southern poles have 42 years in complete darkness, followed by another 42 years in continuous (but dim) sunlight.

Mars, the fourth planet from the sun has two moons but both are tiny.
There are two theories on how they became moons. The first is that they are remnants of Mars itself due to Mars' collision with another planet-like object. The second theory is that they are captured asteroids from the 'nearby' asteroid belt.

Phobos is not round and is an irregular shape being 27 by 22 by 18 kilometres (17 x 14 x 11 miles) in diameter. It rotates around Mars at an average distance of 9,377 km (5,827 mi) and orbits around its planet in 7.7 hours. It is so close and getting closer (two metres per year) that is expected to crash into Mars in 50 million years.

Deimos measures 12.6 km (7.8 mi) in diameter (not completely round) and orbits an average of 23,460 km (14,580 mi) from Mars and orbits Mars every 30.4 hours.

Mars is named after the Roman God of War. Phobos and Deimos were his twin sons (although the moons' names are from Ancient Greece).

Ganymede is the largest moon of the largest planet Jupiter. It is actually the largest moon in the solar system. At 5268km (3270 mi) in diameter, it is 40% the diameter of Earth but only has 2% of Earth's mass. It is larger than both Pluto and Mercury, but its gravity is less than Mercury's.

Ganymede orbits Jupiter in approximately seven days. It is the only moon that has a magnetic field and a thin atmosphere made up of oxygen (O2) and/or ozone (O3). While it has a liquid metallic core, it has an underground saltwater ocean (of ice) that holds more water than all the water on Earth's surface.

While Jupiter had 95 known moons in 2023, Ganymede is one of four 'classical' moons discovered by Galileo Galilei in 1610 along with Callisto, Io, and Europa. The latter two, with Ganymede, exert regular gravitational influence on each other causing their rotations around Jupiter to be synchronised.

These four major moons of Jupiter were the first satellites of planets seen (after our own Moon of course).

Triton is the largest of 13 moons of Neptune the eighth planet from the sun. It was discovered in 1846 only 17 days after Neptune itself was discovered. Triton is the seventh-largest moon in the Solar System with a diameter of 2,710 kilometres (1,680 mi). It is the second-largest planetary moon relative to its planet (after Earth's Moon), and it is larger than all known dwarf planets in the Solar System.

Triton is different from all the other Neptune moons as it revolves backwards (opposite to its planet). This means that Triton cannot have formed in the same region of the Solar system as its planet. It is believed to have originated in the Kuiper belt and been captured by Neptune's gravity. It looks different to other moons in the Solar System as its surface is smooth, with a lack of impact craters. This suggests that the surface is less than 100 million years old. The surface of the moon is covered mostly with frozen nitrogen. Underneath this is frozen water and it has a large core of rock and metal. It has a thin atmosphere of mainly nitrogen with some methane and carbon monoxide. It is one of the few Solar System planets that have geysers.

Triton is named after the son of Poseidon (the Roman equivalent is Neptune). It was thought to be the only moon of Triton until Nereid was discovered in 1949.