Nebulous Trivia Quiz

Answer: True

Note:
In the solar system, distances are vast and kilometres and miles are too small to be the units of distance. An astronomical unit (au or AU) is defined exactly as 1495978707 meters or 149,59,7871km or 92,955,807 miles. It represents the mean of the distance from the centre of the Earth to the centre of the Sun.

So in this question, the overall distance in AU is:

0.37 AU (Mercury) to 1.51 AU (Mars).

Mercury and Venus do not have moons due to their proximity to the sun. At these distances, the Sun's intense gravitational pull is much greater than the gravity each of these planets can exert. Therefore, any potential moons of Mercury and Venus would be captured by the sun.

Earth's Moon is believed to have formed from a massive collision between Earth and another planet-sized object called Theia. The debris from this collision flew into space into a ring and then coalesced into the Moon. This explains why the composition of the Moon is similar to the composition of the Earth. The Moon, with a diameter of over one-quarter of Earth's, is the largest natural satellite in the solar system relative to the size of the planet it orbits.

Mars' two moons are tiny: Phobos, the larger inner moon, is roughly 22-27km (14-17 mi) in diameter, while Deimos, the smaller outer moon, is about 12-13 km (7-8 mi) in diameter. There are two theories on how these moons formed. In the Giant Impact Hypothesis, a planet-sized object hit Mars 4.5 billion years ago, sending debris into orbit that formed a disc. This debris later coalesced together to create the two moons. The massive northern Borealis basin on Mars is believed to have been the impact site. In the Shattered Moon Theory, it is proposed that Phobos and Deimos are the remnants of a larger, single moon that was split into two by a huge impact. The theory that the two moons were once part of the asteroid belt and pulled into Mars' gravitational field has been discredited.

The image shows how the four terrestrial planets compare in size to one another. (The sizes are accurate and proportional, but the distance between each planet is not). The moon, added in exact proportion, is shown for comparative purposes. The two moons of Mars are so small that they would be mere specks on such an image.

Answer: False

2.77-2.80 Astronomical Units

In the asteroid belt, dwarf planet Ceres is the largest object and is the only dwarf planet in the inner solar system. It was first discovered in 1801 by Giuseppe Piazzi. It was thought to be an asteroid for 200 years before it was classified as a dwarf planet in 2006. While Ceres comprises 25% of the mass of the asteroid belt, dwarf planet Pluto is 14 times more massive.

Ceres was on its way to becoming a planet four billion years ago, but its proximity to Jupiter, with its massive gravity, prevented this. Instead, Ceres found a home in the asteroid belt between Mars and Jupiter.

The image is an actual photo of Ceres, named after the Roman Goddess of agriculture, grain crops, fertility, and motherly relationships. (Demeter was the Greek equivalent).

Answer: False

The main asteroid belt spans a distance from the Sun of approximately 2.2 to 3.2 astronomical units (AU)

The total width of the torus shaped asteroid belt is 225 million km (140 million mi). Asteroids in the main belt range from small rocks just a few meters across to nearly 500 km (310 mi) in diameter. Its mass of 2.4 x 10^21 kg is collectively about 4% of the Moon's mass. Over half of the total mass is concentrated in four bodies. Vulcan, an asteroid with a previous volcanic past, has a diameter of about 525km (325mi), which is over half the diameter of Ceres. Pallas, with a diameter of 512 km (318 mi), is almost as large. The fourth biggest body is Hygiea, unusually for an asteroid it is almost completely spherical with a diameter of 430km (267 mi).

The average distance between asteroids larger than 1 km (0.62 mi) is approximately 1 million km (600 000 mi), which indicates the belt is very porous. Spacecraft have traversed the belt without incident and it is doubtful that any spacecraft would have turned its wipers on!.

The image depicts Ceres in the asteroid belt. Interestingly, the asteroid belt is usually depicted with a tightly packed ring of asteroids. While the aim was to produce a sparsely populated asteroid belt, this image, which was drawn by AI, refused to follow this instruction. Instead of trying to produce a more lightly populated belt consistent with the facts, this had to be done without using the words "asteroid belt".

Answer: Ganymede is bigger than Mars

Ganymede orbits the Sun at an average distance of approximately 5.2 Astronomical Units (AU).
Ganymede orbits Jupiter at a mean distance of approximately 1,070,000 km ( 665,000 mi)

Ganymede is the largest satellite in the solar system. It was discovered in 1610 by Galileo Galilei, who also discovered the other three 'classic Jupiter' moons, Callisto, Io, and Europa.

With an average diameter of 5268km (3273 mi), Ganymede is bigger than Mercury (diameter 4,878 km / 3032 mi) but not quite as large as Mars, which has an average diameter of 6780km / 4213 mi.

Several spacecraft (Pioneer 10, Voyager 1 and 2 and Galileo to date) have visited Ganymede. They have discovered that Ganymede is composed of silicate rock and water. NASA has postulated that its vast internal ocean contains more water than the entire water content of the Earth's oceans. Ganymede's surface consists of impact craters dating back four billion years and many grooves and ridges, which are slightly more recent than its craters, and were possibly caused by tectonic activity.

Ganymede is the only solar system satellite to possess an internally generated magnetic field. It is also unusual in that it has an atmosphere. Even more unusual is that the atmosphere comprises oxygen in elemental oxygen, O2 and probably O3 [ozone] forms.

The photo is a composite showing the correct proportions of Earth (right), the Moon (upper left) and Ganymede (lower left)

Answer: True

9.5 Astronomical Units

Ganymede and Titan are both larger than Mercury, with diameters of approximately 5,268 km (3273 miles) and 5,150 km ( 3200 miles), respectively. Earth's Moon, by comparison, is much smaller, with a diameter of about 3,475 km (2159 miles)

Titan is 9.5 AU from the Sun and is one of seven gravitationally rounded moons of Saturn. It orbits around 1.2 million km (0.75 million miles) from Saturn. Its orbit is well outside Saturn's ring system, which extends from 6600km ( 4100 miles) to 480,000 km (300,000 miles) from Saturn's equator. Titan orbits Saturn once every 15 days and 22 hours and is tidally locked in synchronous rotation with Saturn, which means it shows only a single face to its parent planet.

Titan is considered the most Earth-like celestial object in the Solar System, as it is the only known moon with an atmosphere (and denser than Earth's to boot). It also has constant bodies of surface liquid. However, the atmosphere is a mixture of nitrogen and methane, and the rivers and lakes are probably mixtures of methane and ethane. It is also much colder than Earth, as you would expect, with a temperature range of 80-95K (-181C to -166C). There are no apparent craters on the surface of Titan, as there is a large and deep crust of hydrocarbon ice covering a rocky core.

The image is a composite picture showing the comparative sizes of Earth and Titan, though Titan's size is probably larger than its actual size because of its permanent atmospheric haze.

Answer: Part of Pluto's orbit lies within Neptunes' orbit

Neptune has an almost circular orbit (29.8 - 30.3 AU). Pluto's 246-year orbit is very elliptical, ranging from 29.8 - 49.3 AU. It spends 8% of its orbital time within Neptune's orbit. This last occurred between 1979 and 1999.

Pluto is defined as a dwarf planet. Its highly elliptical path is due to its small size and distance from the Sun: The orbit of an object (in this case, Pluto) around its 'parent' (Sun) is a balance between gravitational force and the object's propensity to move in a straight line. If these two forces are equal, a circular orbit ensues (Neptune's, for example), but this is rarely the case. An orbiting object possesses just enough velocity to pull away slightly from its parent (but never to escape it). This slightly larger orbit causes the orbital speed to decrease, so the object will be moving slowly enough to be pulled back in by the parent's gravitational force. Hence, the object's distance from its parent oscillates, resulting in an elliptical orbit. In Pluto's case, the elliptical orbit is extreme.

Pluto and Neptune will never collide: They are in a constant 3:2 resonance, meaning Neptune orbits the Sun three times for every two circuits for Pluto). Additionally while the other planets, their moons and the asteroids orbit the sun as a flat protoplanetary disc, the orbit of Pluto is up to 17 degrees to the horizontal, making the chance of a collision with Neptune even more remote.

Pluto has an equatorial diameter of about 2,377 kilometres (1,477 miles). Pluto is about 20% the width of Earth. A Pluto day is 153 hours. Its rotational axis is 57 degrees to the horizontal and, like Venus, it spins in a retrograde rotation (i.e., from east to west). It has a rocky core surrounded by a water-ice mantle. It is coated with frozen methane and nitrogen frost. It has mountains, valleys, plains, and craters.

The temperature on Pluto is very cold: -226 to -240 degrees Celsius (-375 to -400 degrees Fahrenheit).

The image is a cartoon showing two imaginary planets with crisscrossing orbits.

Answer: True

30-49 Astronomical Units

While Pluto was discovered in 1930, Charon, a moon with a diameter about half as wide as Pluto's, was not discovered until 1978. Four other Plutonian moons were discovered between 2005 and 2012. All are tiny and irregularly shaped: Hydra and Nix are about 50km (30 Mi) at their widest point, Kerebos' widest point is 19km (13 mi), and Styx is only 16 km (10 mi) at its widest point.

Charon and Pluto rotate around each other, though the barycentre is around 960 kilometres (600 mi) above Pluto's surface. They are separated by a short 19 600 (12 170 mi). Their orbital period is 6.4 days. It was this closeness that caused the dimensions of Pluto to be revised downwards, as early sightings of Pluto included Charon characteristics, as the two bodies were not differentiated.

The four much smaller moons orbit much further away, past the orbit of Charon. Their orbital periods range from 20days (Styx) to 38 days (Hydra).

The image is an actual photo showing the relative sizes of Pluto and Charon and their proximity to each other. The four other moons are not shown as their orbit is much further out than Charon.

Answer: False

30-50 Astronomical Units

A circumstellar disc in the outer Solar System, called the Kuiper Belt, extends from the outer orbit of Neptune at 30 AU to approximately 50 AU from the Sun. Similar in concept to the asteroid belt, but 20 times as wide, approximately 100 times as massive. It consists mainly of small bodies like the asteroid belt, but the big difference is that, while asteroids are composed primarily of rock and/or metal, most Kuiper Belt objects are composed largely of frozen "ices". These are volatiles such as methane and ammonia, as well as water. The Kuiper Belt is where several dwarf planets reside: Orcus, Haumea, Quaoar, and Makemake, for example.

Pluto (and its moons) are also in the Kuiper Belt. In fact, its presence here was the reason Pluto was downgraded from planet to dwarf planet. While Pluto meets the first two planetary criteria: orbits the sun; has sufficient mass for a nearly round shape (i.e., gravity-formed), it does not meet the third as it has not 'cleared its orbital neighbourhood' (i.e. it shares space with other celestial objects).

Minor planet 15760Albion was discovered in 1992 and was the first trans-Neptune object (TNO) discovered after Charon in 1978. Since then, over 100 000 Kuiper Belt objects (KBOs) with diameters over 100km (62 mi) have been discovered.

At the outer edge of the Kuiper Belt is another circumstellar disc, called the scattered disc, which overlaps the Kuiper Belt slightly. This is a region of sparsely populated small 'solar system bodies'. It is the place of origin of most periodic comets in the Solar System. It is also where Eris is located, a dwarf planet (replete with its own moon) 96 AU from the sun. By 2011, over 200 scattered disc objects had been discovered, most with eccentric orbits. While some had orbits that reached 30-35 AU, some had orbits that extended way beyond 100 AU.

The image is a representation showing the Kuiper Belt starting at the edge of Neptune's orbit. Pluto's orbit is exaggerated to show that part of its orbit is within Neptune's orbit. However, its elliptical orbit would not extend beyond the outer limit of the Kuiper Belt. If the image was drawn to scale Eris would be out of frame.

Answer: False

2000-200 000 Astronomical Units

The Oort cloud is theorised to be a cloud of billions of icy objects surrounding the Sun, planets, Kuiper Belt and the scattered disc at distances ranging from 2,000 to 200,000 AU. It is theorised as its presence is inferred from comet behaviour.

Its nearest edge is the outside boundary of the solar system, as this is where icy bodies are no longer held in place by the gravity of the Sun. It is far beyond the heliopause, which is the theoretical boundary at 120-123 AU from the Sun, where the solar wind is stopped by the interstellar medium. This marks the edge of the heliosphere.

This theoretical cloud is believed to cover two regions: a disc-shaped inner Oort cloud, which roughly aligns with the solar ecliptic, i.e. everything within the Kuiper belt/scattered disc, and a spherical outer Oort cloud, which encloses the entire solar system. Both regions are therefore in interstellar space. Its innermost edge is over a thousand times as far from the Sun as the Kuiper Belt/scattered disc.

The image shows the relationship of the disc-shaped solar system within the Kuiper Belt and the all-enclosing Oort cloud.

Answer: No

63241.1 AU = 1 light-year

Nearest Nebula: Helix Nebula, 650 light-years
Nearest Galaxy: Canis Major Dwarf Galaxy, 250 000 light years
Nearest Major Galaxy: Andromeda Galaxy (M31), approximately 2,500,000 light-years

There was a time when there was confusion between nebulae and galaxies. So let's try to correctly distinguish between between galaxy and nebula.

The word 'nebula' comes from Latin, meaning 'mist' or 'cloud'. Early astronomers saw what are now known as both galaxies and nebulae as fuzzy objects, as they were both so far away, and they did not have the telescopic power to distinguish between them.

However, nebulae are interstellar clouds of dust and gas. Some nebulae are the remnants of a dying star called a supernova. Other nebulae may coalesce and form new stars over time. This occurs when the clump of dust and gas gets so large that it collapses under its own gravity. This collapse causes the gases, hydrogen and helium at the centre of the cloud, to heat up. This is the beginning of a star.

In the 18th and 19th Centuries, Charles Messier and William Herschel, both esteemed astronomers, catalogued hundreds of 'nebulae'". While they noticed different shapes - such as "planetary" nebulae (which later were established as galaxies) and "spiral" nebulae - they generally assumed these were all gas clouds or star clusters within our own Milky Way, as the Milky Way was thought at the time to be the extent of our universe.

The turning point was the Great Debate in 1920 between astronomers Harlow Shapley and Heber Curtis. Shapley argued that 'spiral nebulae' were small gas clouds located inside the Milky Way, while Curtis argued they were independent galaxies far beyond our own. This was settled in 1923 and 1924 when Edwin Hubble identified cepheid variable stars in the Andromeda Nebula and was therefore able to calculate their distance, proving Andromeda was far outside the Milky Way, definitively transforming "spiral nebulae" into galaxies.

So, before 1924, a nebula was any "fuzzy" patch of light in the sky - a cloud of dust and gas within a galaxy. while galaxy referred only to the Milky Way, a massive system of billions of stars and nebulae, so both were seen as the same type of object. However, after Hubble's work, a nebula was defined as a cloud of dust and gas within a galaxy, which was still defined as a massive system of billions of stars and nebulae, but there were many, many galaxies (not just the one Milky Way), and nebulae are small components inside galaxies.

So the main difference is size and composition: A nebula is a cloud of dust and gas, usually tens to hundreds of light-years across. A galaxy is usually thousands to hundreds of thousands of light-years across. Nebulae are one of the many things that galaxies are made of, along with stars, black holes, cosmic dust and dark matter.

The image shows the Helix nebula, a 'nearby' nebula 650 light-years away, taken by the Hubble telescope through several filters. It is known as the 'Eye of God', and it formed from a dying intermediate-sized star that discarded its outer layers, leaving a central white dwarf behind.