My Science School

In 1610, when Galileo Galilei first began to look at Saturn through his homemade telescope, he thought that Saturn's rings were actually two moons. He called these moons "Saturn's ears". Forty -five years later, the astronomer Chris tiaan Huygens realized that these moons were actually a series of beautiful rings surrounding the planet. With the photographs provided by the Pioneer and Voyager probes, scientists now know more about these rings than ever before.

Saturn is the second largest planet of our solar system but this fact does not make it unique and attractive. The most beautiful and amazing thing related to Saturn is its wonderful ring system which surrounds the planet making it the most mysterious planet of our solar system. This ring system is composed of many ringlets and gaps and it is inclined to the orbital plane of Saturn by 27 degrees. The theory behind this amazing ring system is not complete till today there are lots of mysteries behind them and their origin.

History of the discovery of ring system around Saturn is also very interesting. Galileo was the first person who turned up his self-made telescope towards the sky. In 1610, he looked at Saturn and found that there is something on the both side of Saturn. So he concluded that “Saturn is not a single body but it is composed of three bodies. Middle one is three times larger than the side ones.” He called them Saturn’s children. In 1612, the plane of the ring with respect to Earth got changed and ring got vanished. Now Galileo got totally puzzled he wrote that Saturn had swallowed its children in fear of losing them in the space. In 1613, once again plane of ring changed and the ring appears again so Galileo was not able to conclude anything from these observations except surprise. He also called them “Ears of Saturn”.

In 1655, Christiaan Huygens used the 50 times more powerful telescope than that used by Galileo and concluded, “Saturn is surrounded by thin and flat rings which are somewhere touched to Saturn and inclined to elliptic.” Robert Hooke also noted the casting of the shadow of Saturn on the plane of the ring. In 1675, Giovanni Domenico Cassini noted that Saturn ring is composed of many ringlets with gaps between them. The largest gap was named Cassini Division after his name. Its width is 4800 km and is situated between ring A and Ring B.

Picture Credit : Google

Jupiter has been contracting and cooling down since its birth 4.6 billion years ago. It was once an incredible 700,000km (435,000 miles) in diameter — over five times its present size. Jupiter shrinks by around 2.5cm (1 in) each year, and as it does so, it generates an enormous amount of heat. Scientists now know that Jupiter gives out more heat than it receives from the Sun.

A feature that makes Jupiter interesting is that it radiates almost twice as much heat as it receives from the sun; this is possible only because it produces its own heat. Although Jupiter has almost enough hydrogen to qualify as a small star, the mysterious excess heat has another explanation: The planet is warmed by energy left over from its formation 4.6 billion years ago.

Jupiter is five times farther from the sun than the Earth is; at this great distance, it receives a fraction of the sun’s warming rays, keeping the planet very cold. Based on the energy Jupiter receives from the sun, astronomers expected it to have a temperature of 105 kelvins (minus 271 degrees Fahrenheit). But an analysis of the infrared light and radio waves received from Jupiter revealed its temperature to be 125 kelvins (minus 235 degrees Fahrenheit). To account for the difference, Jupiter must be generating its own heat at a rate comparable to what it receives from the sun.

During the solar system’s earliest years, Jupiter and the other planets formed through the force of gravity; clouds of gas and dust particles contracted under their own weight, eventually becoming solid bodies with atmospheres. Unlike most of the planets, Jupiter, whose volume is mostly gas, is still contracting. As its material falls toward the planet’s center, it releases stored gravitational energy, eventually becoming heat.

None of the gas giants has a surface like the terrestrial planets. Instead, the gases that make up Jupiter are but under more and more pressure the deeper they are, so that they gradually change from a gas into a liquid. Further in, the pressure is so great that the gases are squeezed into solid form.

As a gas giant, Jupiter doesn’t have a true surface. The planet is mostly swirling gases and liquids. While a spacecraft would have nowhere to land on Jupiter, it wouldn’t be able to fly through unscathed either. The extreme pressures and temperatures deep inside the planet crush melt and vaporize spacecraft trying to fly into the planet.

Jupiter's appearance is a tapestry of colorful cloud bands and spots. The gas planet likely has three distinct cloud layers in its "skies" that, taken together, span about 44 miles (71 kilometers). The top cloud is probably made of ammonia ice, while the middle layer is likely made of ammonium hydrosulfide crystals. The innermost layer may be made of water ice and vapor.

The vivid colors you see in thick bands across Jupiter may be plumes of sulfur and phosphorus-containing gases rising from the planet's warmer interior. Jupiter's fast rotation—spinning once every 10 hours—creates strong jet streams, separating its clouds into dark belts and bright zones across long stretches.

With no solid surface to slow them down, Jupiter's spots can persist for many years. Stormy Jupiter is swept by over a dozen prevailing winds, some reaching up to 335 miles per hour (539 kilometers per hour) at the equator. The Great Red Spot, a swirling oval of clouds twice as wide as Earth, has been observed on the giant planet for more than 300 years. More recently, three smaller ovals merged to form the Little Red Spot, about half the size of its larger cousin. Scientists do not yet know if these ovals and planet-circling bands are shallow or deeply rooted to the interior.

Jupiter has a very faint system of rings that was discovered by the Voyager space probes in the 1970s. There are three distinct rings, all formed by material knocked off the planet's four inner moons. Adrastea, Metis, Amalthea and Thehe all orbit very close to the planet, and are constantly bombarded by meteorites. The dust blasted from these tiny moons is added to the planet's rings.

Early in its mission to Jupiter, the Galileo spacecraft made observations that provided confirmation on how Jupiter's rings were formed, as the dust was seen to coincide with small moon locations: the two Gossamer rings near the small moons Amalthea and Thebe and the main ring near Adrastea and Metis. Scientists had long believed that dust coming off of Adrastea and Metis formed the main ring, but were unsure of the origin of the Gossamer rings.

Jupiter's rings are formed from dust particles hurled up by micro-meteor impacts on Jupiter's small inner moons and captured into orbit. If the impacts on the moons were any larger, then the larger dust thrown up would be pulled back down to the moon's surface by gravity. The rings must constantly be replenished with new dust from the moons to exist.

Picture Credit : Google

Jupiter, with its 67 known moons, can be viewed as a miniature solar system revolving around the Sun. Four of these moons are large enough to be visible with even a small telescope. These so-called Galilean satellites — Io, Europe, Ganymede, and Callisto — are of nearly planetary size.

But scientists haven’t been able to explain how these moons became so big. Now, scientists have conducted a study to suggest that Saturn might be to blame.

During the solar system’s earliest years, a huge rotating disk of gas and dust surrounded the Sun. The dust quickly glommed together into pebble-sized chunks, out of which the planets and most moons formed. As Jupiter came together, it acquired its own disk by sweeping clean a gap in the gaseous disk around the Sun. It’s likely that the Galilean moons began forming within Jupiter’s circumplanetary disk. But even as the giant collected gas from the circumsolar disk, it was carving the gap that would cut off its disk from material that would have helped build its moons.

René Heller (University of Göttingen, Germany), who was not involved in the new study, notes that astronomers have long been lacking a mechanism to deliver solid material to Jupiter’s circumplanetary disk. "This aspect has often been overlooked or simplified in previous models for the formation of the Galilean satellites; we assumed that the gas and dust was just there, out of nowhere," he says.

One of the astronomers who investigated this impasse is Thomas Ronnet (Astrophysical Laboratory of Marseille,France). He realized that Jupiter’s massive neighbor Saturn might be involved. When the planets were forming, their orbits were still migrating — resulting in a solar system that looked very different from the one we see now, Saturn in particular is thought to have been in an orbit much closer to that of Jupiter. So Saturn could have dispersed pebbles that were stuck in the midplane of the circumsolar disk, allowing Jupiter to capture them.

Several probes have flown as far as Jupiter. In 1973, the Pioneer 10 probe flew by the giant planet taking close-up photographs. The Voyager 1 and 2 probes, launched in 1977, flew by the four gas planets — Jupiter, Saturn, Uranus and Neptune — taking pictures and measurements. The primary Voyager missions were completed in 1989, but both craft are now continuing into the depths of the outer Solar System at a speed of over 56,300km/h (35,000mph). Even at this speed it could take the probes over 30,000 years to reach the outer edges of the Solar System!

The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA in separate months in the summer of 1977 from Cape Canaveral, Florida. As originally designed, the Voyagers were to conduct close-up studies of Jupiter and Saturn, Saturn's rings, and the larger moons of the two planets.

To accomplish their two-planet mission, the spacecraft were built to last five years. But as the mission went on, and with the successful achievement of all its objectives, the additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible -- and irresistible to mission scientists and engineers at the Voyagers' home at the Jet Propulsion Laboratory in Pasadena, California.

As the spacecraft flew across the solar system, remote-control reprogramming was used to endow the Voyagers with greater capabilities than they possessed when they left the Earth. Their two-planet mission became four. Their five-year lifetimes stretched to 12 and more.

Eventually, between them, Voyager 1 and 2 would explore all the giant outer planets of our solar system, 48 of their moons, and the unique systems of rings and magnetic fields those planets possess.

Had the Voyager mission ended after the Jupiter and Saturn flybys alone, it still would have provided the material to rewrite astronomy textbooks. But having doubled their already ambitious itineraries, the Voyagers returned to Earth information over the year that has revolutionized the science of planetary astronomy, helping to resolve key questions while raising intriguing new ones about the origin and evolution of the planets in our solar system.

The great red spot is Jupiter’s fiercest storm. It is a hurricane over three times as large as Earth that has been raging continuously for over 300 years. Made from gases such as ammonia and clouds of ice, it towers 8km (5 miles) over surrounding clouds. Damp air rising inside the Great Red Spot causes the clouds to rotate, coming full circle every six Earth days.

The largest and most powerful hurricanes ever recorded on Earth spanned over 1,000 miles across with winds gusting up to around 200 mph. That’s wide enough to stretch across nearly all U.S. states east of Texas. But even that kind of storm is dwarfed by the Great Red Spot, a gigantic storm in Jupiter. There, gigantic means twice as wide as Earth.

With tumultuous winds peaking at about 400 mph, the Great Red Spot has been swirling wildly over Jupiter’s skies for the past 150 years—maybe even much longer than that. While people saw a big spot in Jupiter as early as they started stargazing through telescopes in the 1600s, it is still unclear whether they were looking at a different storm. Today, scientists know the Great Red Spot is there and it’s been there for a while, but they still struggle to learn what causes its swirl of reddish hues.

Understanding the Great Red Spot is not easy, and it’s mostly Jupiter’s fault. A planet a thousand times as big as Earth, Jupiter consists mostly of gas. A liquid ocean of hydrogen surrounds its core, and the atmosphere consists mostly of hydrogen and helium. That translates into no solid ground like we have on Earth to weaken storms. Also, Jupiter’s clouds obstruct clear observations of its lower atmosphere. While some studies of Jupiter have investigated areas in its lower atmosphere, orbiting probes and telescopes studying the Great Red Spot can only see clouds scattered high in the atmosphere.

Studies predict Jupiter’s upper atmosphere has clouds consisting of ammonia, ammonium hydrosulfide, and water. Still, scientists don’t know exactly how or even whether these chemicals react to give colors like those in the Great Red Spot. Plus, these compounds make up only a small part of the atmosphere. “We’re talking about something that only makes up a really tiny portion of the atmosphere,” Simon said. “That’s what makes it so hard to figure out exactly what makes the colors that we see.”

Other experts agree with the leading theory that deep under Jupiter’s clouds, a colorless ammonium hydrosulfide layer could be reacting with cosmic rays or UV radiation from the sun. But Simon said many chemicals turn red under different situations. “That’s the problem,” she said. “Is it turning the right color red?” Under the right conditions, ammonium hydrosulfide might be.

With the Great Red Spot and other reddish parts of Jupiter, coloring may result from multiple factors, as opposed to just ammonium hydrosulfide. “Ideally, what you’d want is a mixture with the right components of everything that you see in Jupiter’s atmosphere at the right temperature, and then irradiate it at the right levels,” Simon said. Ultimately, Simon and Loeffler said solving the Great Red Spot’s mystery will take more experiments combining chemicals under the right temperatures, light exposures and radiation doses. “What we are trying to do is design lab experiments more realistic to Jupiter’s atmosphere,” Simon said.  

There are three layers of clouds on Jupiter, each made of different molecules. The outer cloud deck is made from ammonia, the middle deck from a combination of ammonia and sulphur, and the inner deck from ordinary water clouds. Heat from Jupiter’s interior, and the planet's rapid rotation, cause ferocious winds that create the cloud patterns. The white hands are areas of rising gas, called zones. The dark hands are called belts; we are areas of falling gas. In these belts we are seeing much further into Jupiter, so they appear darker.

Jupiter’s atmosphere is doing some pretty funky stuff, and we don’t fully understand all of what’s going on. We know that the light stripes and dark stripes are made of slightly different gases, and that at the boundaries of these stripes are narrow regions of high wind, called jets, which push the nearby atmosphere around with it, and that the bands are relatively stable.

The light stripes seem to be made of cold gas which is coming up towards the surface of the atmosphere of Jupiter, and the dark stripes are doing the opposite (warmer gas, sinking down towards the centre of the planet). The light ones are light because there’s a lot of ammonia in the upper atmosphere of Jupiter, and as it cools, it forms pale clouds, like the clouds in our sky. If the gas warms up, the clouds will disappear, and what we’re seeing as dark bands are actually a deeper, darker layer of clouds. However, the sun also has upwellings of gas and regions where gas is sinking back, and the surface of the sun looks like boiling water - there’s no order there. So why does Jupiter have ordered bands and not just look like a roiling mess?

At a very basic level, it’s because those jets of wind running around the planet are there. These jets form a boundary for the gas. When gas faces a strong wind, it’s going to be redirected in the direction of the wind instead of continuing the way it was originally headed. Because the direction of the wind jets alternates as you go from the equator to the poles, the boundaries of the jet and the band forms eddies and whirlpools of gas, which helps to pull the gas along with the wind. As a result, the jets describe the edges of the different bands of coloured gas, and direct the motion of the gas within each stripe. The part that we don’t yet understand is why those jets exist in the first place. 

Broadly, there are two main ideas - one is that this is turbulence at the surface level, like clouds in the upper atmosphere of the earth. Perhaps there was some turbulence - a little bit of bumpy gas, and it ran into another patch. As patches of turbulence catch up to each other, they can combine, and form one bigger piece of turbulence - called a cascade. If there’s a constant source of the little eddies of turbulence, then you can maintain bigger turbulence (like the wind jets) just by tossing the little things together. However, this method is bad at keeping the stable winds we see, so this isn’t a great description.

The second idea is that since Jupiter is rotating relatively quickly, and is basically all gas, the gas can form cylindrical shells of material that rotate a little differently as you go out away from the centre of the rotation. However, we have all noticed that planets are not cylinders, they are spheres. But if you start with a cylinder, and carve into it, you can create a sphere. So these bands appear as the surface of Jupiter cuts into different layers, as you get closer to the poles. (As another illustration, if you sharpen a wood pencil, you wind up with a stripe of pencil lead, a stripe of the wood that’s been cut into, and the outer layer of the pencil that you didn’t touch, if you look at it from the side.) The main problem with this method is that generally it doesn’t make enough bands.

Since neither of these ideas really sets out a comprehensive solution to the whys of Jupiter’s atmosphere, for the moment we have to be stuck with observing the banded clouds of Jupiter and the jets that drive them, in hopes that the details of their behaviour will hint towards one answer over another.

Jupiter formed from the same cloud of gases as the Sun. If this giant planet had continued to grow, its core would have ignited into a nuclear furnace, and Jupiter would have become a star. Theoretically, Jupiter could still become a star. If it expands to forty times its present mass, then self-sustaining nuclear reactions will begin within its core — the defining factor of a star.

Jupiter is often called a ‘failed star’ because, although it is mostly hydrogen like most normal stars, it is not massive enough to commence thermonuclear reactions in its core and thus become a ‘real star’. But the term ‘failed star’ is a bit of a misnomer. Theoretically, any object at all could be made into a star, simply by adding enough matter to it. With enough mass, the internal pressure and temperature of the object will reach the threshold needed to start thermonuclear reactions. That threshold is the least for the simplest element, hydrogen. In order to turn Jupiter into a star like the Sun, for example, you would have to add about 1,000 times the mass of Jupiter. But, to make a cooler ‘red dwarf’ you would only need to add about 80 Jupiter masses. Although the exact numbers are still a bit uncertain, it is possible that a ‘brown dwarf’ could still form (in which deuterium, rather than hydrogen, fuses in the star’s core) with only about 13 Jupiter masses. So, Jupiter cannot and will not spontaneously become a star, but if a minimum of 13 extra Jupiter-mass objects happen to collide with it, there is a chance it will.

Although asteroids are very small compared to planets, some have a powerful enough gravitational pull to attract natural satellites. As the space-craft Galileo travelled towards Jupiter in 1993, it flew by an unusual pair of asteroids called Ida and Dactyl. Ida is 56km (35 miles) long, and was found to have a moon, Dactyl, that is smaller than 1.6km (1 mile) across (above).

A big asteroid, named Florence, flew about four-and-a-half million miles from Earth back in September. Astronomers took a look at it with radio telescopes. And they discovered that it wasn’t alone. Two small moons orbit the asteroid. One is about the length of two football fields, while the other spans three football fields.

No one was really surprised to find the little moons. That’s because more than 300 asteroids have known moons, including quite a few with two of them, and some that have three.

The first asteroid moon was discovered in pictures that were snapped 25 years ago today. The Galileo spacecraft was passing through the asteroid belt on its way to Jupiter. It flew close to Ida, an asteroid that’s about 35 miles long. When mission scientists looked at the pictures of Ida a few days later, they discovered a mile-wide companion. They named it Dactyl, after creatures from Greek mythology that lived on Mount Ida.

The most likely way for an asteroid to get a moon is through a collision with another asteroid. If the impact is at the right speed and angle, it can chip off a chunk of rock and send it into orbit. If the impact is too strong, though, the debris sails away into space, leaving the parent asteroid behind.

In some cases, a collision may split an asteroid in two. That creates a pair of twins — two asteroids of roughly equal size orbiting the Sun together.

Scientists are interested in finding out more about asteroids. Many are thought to contain minerals and metals that could benefit industries on Earth. The Near Earth Asteroid Rendezvous (NEAR) space probe (below) visited two asteroids, Mathilde and Eros, in 1997 and 1998. It took photographs that showed Mathilde to be entirely covered by craters. Soon, expeditions may be launched from Earth to mine asteroids in space.

Asteroids are minor planets, especially of the inner Solar System. Larger asteroids have also been called planetoids. These terms have historically been applied to any astronomical object orbiting the Sun that did not resolve into a disc in a telescope and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered that were found to have volatile-rich surfaces similar to comets, these came to be distinguished from the objects found in the main asteroid belt. In this article, the term "asteroid" refers to the minor planets of the inner Solar System, including that co-orbital with Jupiter.

There exist millions of asteroids, many the shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets. The vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or co-orbital with Jupiter (the Jupiter Trojans). However, other orbital families exist with significant populations, including the near-Earth objects. Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups: C-type, M-type, and S-type. These were named after and are generally identified with carbon-rich, metallic, and silicate (stony) compositions, respectively. The sizes of asteroids varies greatly; the largest, Ceres, is almost 1,000 km (600 mi) across and massive enough to be a dwarf planet.

Asteroids are somewhat arbitrarily differentiated from comets and meteoroids. In the case of comets, the difference is one of composition: while asteroids are mainly composed of mineral and rock, comets are primarily composed of dust and ice. Furthermore, asteroids formed closer to the sun, preventing the development of cometary ice. The difference between asteroids and meteoroids is mainly one of size: meteoroids have a diameter of one meter or less, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials.

Although most asteroids drift harmlessly around the Sun for billions of years, some are occasionally knocked out of their orbits. Some of these asteroids pass very close to Earth. In 1994, an asteroid measuring 10m (32ft) in diameter passed within 105,000km (65,000 miles) of our planet — around one third of the distance to the Moon. If a large asteroid were to collide with Earth, the impact could he powerful enough to annihilate all life on the planet. Vast waves of water, dust and fire would flatten cities in seconds, and billions of tonnes of dust entering the atmosphere would block out the Sun’s light for hundreds of years.

This is a list of examples where an asteroid or meteoroid travels close to the Earth. Some are regarded as potentially hazardous objects if they are estimated to be large enough to cause regional devastation.

Near-Earth object detection technology greatly improved about 1998, so objects being detected as of 2004 could have been missed only a decade earlier due to a lack of dedicated near-Earth astronomical surveys. As sky surveys improve, smaller and smaller asteroids are regularly being discovered. The small near-Earth asteroids 2008 TC3, 2014 AA, 2018 LA and 2019 MO are the only four asteroids discovered before impacting into Earth (see asteroid impact). Scientists estimate that several dozen asteroids in the 6–12 m (20–39 ft) size range fly by Earth at a distance closer than the moon every year, but only a fraction of these are actually detected.

There are many theories about how the asteroid belt developed. Some astronomers believe that it is the remains of a planet that was torn apart billions of years ago. Conversely, others argue that the asteroids in the belt are pieces of a planet that never formed. According to this theory, the immense gravitational pull of the young planet Jupiter prevented the rocks from forming one large body.

The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars, that is occupied by a great many solid, irregularly shaped bodies, of many sizes but much smaller than planets, called asteroids or minor planets. This asteroid belt is also called the main asteroid belt or main belt to distinguish it from other asteroid populations in the Solar System such as near-Earth asteroids and Trojan asteroids.

About half the mass of the belt is contained in the four largest asteroids: Ceres, Vesta, Pallas, and Hygiea. The total mass of the asteroid belt is approximately 4% that of the Moon, or 22% that of pluto, and roughly twice that of Pluto's moon Charon (whose diameter is 1200 km).

The asteroid belt formed from the primordial solar nebula as a group of planetesimals. Planetesimals are the smaller precursors of the protoplanets. Between Mars and Jupiter, however, gravitational perturbations from Jupiter imbued the protoplanets with too much orbital energy for them to accrete into a planet. Collisions became too violent, and instead of fusing together, the planetesimals and most of the protoplanets shattered. As a result, 99.9% of the asteroid belt's original mass was lost in the first 100 million years of the Solar System's history. Some fragments eventually found their way into the inner Solar System, leading to meteorite impacts with the inner planets. Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter. At these orbital distances, a Kirkwood gap occurs as they are swept into other orbits.

Classes of small solar System bodies in other regions are the near-Earth objects, the centaurs, the Kuiper belt objects, the scattered disc objects, the sednoids, and the Oort cloud objects.

Bode’s law states that there is a pattern in the way the planets are spaced from the Sun. Bode started with the number 0, then took 3, and began doubling: 0, 3, 6, 12, 24, 48, 96, 192, 384, 768. He then divided each number by 10 and added 4. The numbers that he discovered were similar to planetary distances from the Sun in astronomical units. According to Bode's theory, there should be a planet between Mars and Jupiter.

The concept was devised and first published in 1766 by Johann D. Titius, a German mathematician and physicist, based on the six planets known at the time: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. The German astronomer Johann E. Bode popularized the law in a book published in 1772, and it became associated with his name.

The law relates the mean distances of the planets from the sun to a simple mathematic progression of numbers. To find the mean distances of the planets, beginning with the following simple sequence of numbers:

0   3   6   12   24   48   96   192   384

With the exception of the first two, the others are simple twice the value of the preceding number.

Adding 4 to each number results,

4   7   10   16   28   52   100   196   388

Then dividing by 10

0.4   0.7   1.0   1.6   2.8   5.2   10.0   19.6   38.8

Most of the asteroids in the Solar System orbit the Sun in a band between Mars and Jupiter. This band is nearly 550 million km (340 million miles) wide and is called the asteroid belt. There are billions of asteroids in this zone, each moving independently around the Sun and spaced many thousands of kilo-metres from each other.

The asteroid belt is located between the inner and the outer planets and is home to thousands of rocks and debris known as asteroids and some of the dwarf planets. All of these orbit the Sun.

Some asteroids do orbit in space near to Earth and some are forced out of the asteroid belt by gravity and sent towards the outer solar system instead. There are hundreds of thousands of asteroids in the asteroid belt, but almost half of the entire mass is made up of just four objects. These objects are the dwarf planet Ceres, and three other asteroids called Vesta, Pallas and Hygiea. The diameters of Vesta, Pallas and Hygiea are over 400km and Ceres is even bigger at 950km diameter.

Of the many thousands of asteroids in the asteroid belt, Ceres is the only one large enough to be classified as a “dwarf planet”. Apart from these four objects, the remaining objects in the asteroid belt range in size from small rocks right down to dust particles.

The asteroid belt is between the planets Mars and Jupiter. It is located about 2.2 to 3.2 Astronomical Units (AU) from the Sun. That is somewhere between 329-478 million km away. The asteroid belt is huge and the space between each of the asteroids is over 600,000 miles. The circumference of Earth is only 24,901.45 miles, which means that the distance between objects in the asteroid belt is more than 24 times the circumference of Earth.