The Solar System is a group of dwarf planets, asteroids, and comets that orbit around the Sun. The planets in the Solar System include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

The Sun is also part of the Solar System, as are dwarf planets like Pluto, moons like the Moon, and the asteroid belt between Mars and Jupiter.

How Old is the Solar System?

The Solar System’s age has been a fascinating area of research for scientists for many years. Through a lot of studies, it has been discovered that the Solar System is almost 5 billion years old, more specifically, 4.6 billion years old.

The fact that we can know the Solar System’s age is great, but how exactly do scientists discover this information? Well, it all has to do with the study of meteorites. Meteorites, believed to be the oldest accessible material in existence, have allowed scientists to trace the age of the Solar System over 4.6 billion years. Meteorites are not the only ancient materials kicking about the universe, as some rocks on Earth date back as far as 3.8 billion years ago.

We have not always had such advanced, in-depth knowledge about the history of the Solar System. In fact, until the Late Middle Ages–Renaissance period, most people believed that Earth was a completely stationary planet at the center of the universe. It was also believed that Earth differed from the other celestial objects in the Solar System. For example, a Greek philosopher named Aristarchus of Samos proposed the idea of the Sun being at the center of the Solar System. However, the belief was by no means widely held. It was not until Nicolaus Copernicus, a Renaissance polymath in the 15th century, formulated a mathematical model of the universe with the Sun at the center of the universe that the belief was more solidified. This mathematical model is known as ‘heliocentric,’ meaning the Sun is at the center.

A couple of hundred years later, in the 17th century, Galileo made several important discoveries that improved our understanding of the universe. Notably, Galileo discovered that the Sun was covered in sunspots and that Jupiter had four satellites orbiting around it. After this, many great minds expanded on Galileo’s discoveries, including Christiaan Huygens, a Dutch mathematician, physicist, astronomer, and inventor. Huygens, widely believed to have been one of the greatest scientists of all time, discovered Saturn’s moon, Titan, and the shape of the rings surrounding the planet. Many important discoveries were made in the years following that laid the foundation for what we now know about the universe’s history.

How was the Solar System Formed?

Scientists believe that the solar system started as a loose cloud of gas and dust, and a force called gravity pulled the parts of the cloud together into clumps.

Over millions of years, these clumps formed everything that the solar system is made up of today, which includes the Sun and everything that orbits it. This consists of eight planets, asteroids, comets, and other small, icy objects. Yet, even with all these things, most of the solar system is in space!

The Sun, the largest object in the solar system, is at the center, has a diameter of 865,000 miles (ca. 1,392,083 km), and contains more than 99% of all the material in the solar system. It is a very hot ball of hydrogen and helium gases constantly changing, and its core temperature is more than 15,600,000 degrees Celsius. This process gives out large amounts of energy, which living things on Earth depend on, in the form of light and heat.

The solar system is one small part of a huge system called the Milky Way Galaxy, which is just one of the billions of galaxies that make up the universe. This puts the vast size of space into perspective! The solar system orbits around the center of the Milky Way Galaxy around once every 225 million years.

Each planet in our solar system orbits the sun at different speeds depending on how far away it is. The difference between the orbit times of the closest and the farthest planet from the sun is a massive 60,137 days!

The Order of the Planets in the Solar System?

As mentioned, eight planets in our solar system orbit around the Sun. Starting with the closest planet to the Sun, the order of planets in our solar system is as follows:

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune

You may look at this list and feel like something is missing. This is because, until fairly recently, Pluto was also considered a planet. However, Pluto is now classified as a dwarf planet, meaning it is not included in the eight main planets in our solar system.

What is the Farthest Planet from Earth?

We know the order of the planets about the Sun, but what is the farthest planet from Earth? Well, the simple answer to that question is Saturn. So let’s dive deeper into Saturn, the sixth planet from the Sun and the farthest planet from Earth.

Saturn is the second-largest planet in our solar system, beaten only by Jupiter. This huge planet is essentially just a huge ball of hydrogen and helium encompassed by its iconic rings. Discovered in 1610 by the Italian astronomer Galileo Galilei, Saturn was first viewed through a telescope. It was then named Saturn, after the Roman god of agriculture and wealth.

  • Is there life on Saturn?

One of the questions everyone asks about space is: ‘Is there potential for life?’ Unfortunately, as far as we know, Saturn’s atmosphere cannot support life. The planet has an extremely cold climate, with average temperatures dropping below -176 degrees Celsius. The environment and the pressures and materials on Saturn make it pretty inhospitable. The same cannot be said for Saturn’s moon, however. Saturn has a whopping 82 moons, many of which contain internal oceans and would be capable of supporting life.

  • How big is Saturn?

As it is the second-largest planet in the solar system, we know that Saturn is big, but just how big is it? Saturn is nine times wider than Earth and has a radius of 36,183.7 miles (ca. 58,232 km) and a total mass of 5.6836 × 1026 kg.

  • Time on Saturn

Another fun fact about Saturn is that it has the solar system’s second-shortest day on any planet. One day on Saturn only lasts 10.7 hours, measured by the time it takes Saturn to make one full rotation. Moreover, a year on Saturn is around 29.4 Earth years, which is the time it takes Saturn to make one complete orbit around the Sun.

  • Saturn’s famous rings

The most defining feature of Saturn is its rings, but what are they made of? The rings are believed to be pieces of comets, asteroids, or shattered moons that were broken up before they reached Saturn. They would likely have been torn apart by Saturn’s extremely powerful gravity. Each ring comprises billions of particles of ice and rock, which are coated in other materials, like dust. The size of these particles ranges greatly from tiny ones to ones as big as a house. There are even a few particles that are as large as mountains.

Saturn’s rings extend around 175,000 miles (ca. 281,635 km) out from the planet, each moving at a different speed. Saturn’s rings are, for the most part, named alphabetically in the order that they were discovered. The main crews are called A, B, and C, and the less prominent ones are called D, E, F, and G. The exception is a gap measuring 2,920 miles (ca. 4,699 km) in width called the Cassini Division that separates Rings A and B. Beginning at Saturn and moving outward, the order of the rings are:

  • D ring
  • C ring
  • B ring
  • Cassini Division
  • A ring
  • F ring
  • G ring
  • E ring

Much farther out, there is a very faint ring called the Phoebe ring in the orbit of Saturn’s moon Phoebe.

  • The formation of Saturn

Saturn came about with the rest of the solar system around 4.5 billion years ago when gravity pulled swirling gas and dust in to form the planet. Then, around 4 billion years ago, Saturn took its place as the sixth planet from the Sun in the outer solar system.

  • The structure of Saturn

Much like Jupiter, Saturn is primarily made up of hydrogen and helium. At its center, Saturn has a dense core of metals, such as iron. This is encompassed by rocky material and other compounds that have been solidified through extreme pressure and heat. Its body is surrounded by liquid metallic hydrogen inside a layer of liquid hydrogen.

Which Planet is Farthest from the Sun?

Neptune is the planet farthest from the Sun.

Once upon a time, we had more than eight planets in our solar system. The answer to which planet is farthest from the sun was quite different. Before 2006, Pluto was considered the 9th planet in the solar system and the farthest planet from the sun. On average, Pluto was 3.6 billion km from the center of the solar system. It is so far away that one year on Pluto is the same as 248 years on Earth!

After 2006, the answer to which planet is farthest from the sun changed. NASA created a new classification system for celestial objects to be considered planets. In the new system, Pluto was labeled as a dwarf planet and removed from the list of solar system planets.

The gas giant, Neptune, is now classified as the farthest planet from the Sun because its orbit extends to 4.5 billion kilometers from it. It is so far away that it is impossible to view Neptune with the naked eye. Only one mission into space has flown close enough to photograph it.

Dwarf Planets in the Solar System

The planets that became dwarf planets in the new classification were named that because they aren’t big enough to clear out their orbits of all the asteroids, comets, and chunks of rock. Pluto, and its moon Charon, is in this category because there are many other rocks in their orbit.

The farthest dwarf planet that we know of is Eris. A planetary body so far past Pluto that it takes around 557 to 558 years to orbit the sun once!

Solar System Facts for KS2

  • For thousands of years, people thought that the Earth was at the center of the universe, as they had no idea about the solar system.
  • Astronomers like Nicolaus Copernicus, Galileo Galilei, and Isaac Newton contributed to the new model that explained the movement of the planets in the solar system, with the Sun at the center.
  • There are eight planets identified within our solar system. This number excludes the sun, a star, and Pluto, which was reclassified in 2006 as a dwarf planet.
  • Mercury and Venus are the only planets in our solar system not to have moons orbiting them.
  • Jupiter is the biggest planet in the Solar system — so big that it can fit all the other seven planets inside it!
  • One year on Neptune is the same as 165 years on Earth.
  • Despite appearances, the rings surrounding Saturn are only 30 feet (ca. 9 m) thick.
  • The Sun is a star, which is a huge ball of burning gas that gives off light and heat.
  • As well as the planets in the solar system, there are five dwarf planets: Pluto, Ceres, Eris, Makemake, and Haumea.
  • Jupiter’s largest moon, Ganymede, has a salty ocean that contains more water than Earth’s!
  • Mercury was named after the fast-footed messenger of the Roman gods because it orbits the quickest around the Sun.
  • Each year, about 28,000 tonnes of extraterrestrial material enter our atmosphere.
  • In the nineteenth century, Tsar Alexander of Russia had a sword made from an ‘iron’ meteorite.
  • Venus shines brightly in Earth’s sky because the cloud layer reflects most of the sunlight.
  • Neptune radiates 2.6 times more heat than it receives from the sun — this sign that it has an internal heat source.
  • Light from the Sun takes about eight minutes to reach Earth and takes more than 2.5 hours to travel to Uranus.
  • The highest mountain known to man is on an asteroid called Vesta. Measuring a whopping 22 km in height, it is three times as tall as Mount Everest!
  • The Earth’s Moon has approximately the same surface area as the continents of North and South America.
  • Jupiter can be seen with the naked eye from Earth as a bright, silver ‘star’ in the night sky.
  • Mars is as cold as the South Pole — its average temperature is roughly -60 °C.
  • Outside our solar system, the nearest star to Earth is a red dwarf star called Proxima Centauri, which is 4.24 light-years away.
  • Saturn’s rings are made of billions of ice-covered rock fragments and dust particles.
  • Mars was named after the Roman god of war because it appears to be the color of spilled blood.
  • The south polar ice cap on Mars is much larger than the north polar ice cap, and the southern winter is considerably longer.
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