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Our Solar System

We humans have lived in the solar system for aeons. But how much do we know about the solar system? Here's a basic start and explanation of the Solar System.




Our Solar System

Our Solar System formed about 4.6 billion years ago from a nebular cloud and is located at a radius of about 27,000 light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust.  


Our Solar System is also home to 8 planets, 5 dwarf planets, more than 200 moons, about 959,000 known asteroids, and more than 3600 known comets, including the famous Halley's comet. All of these listed about orbit our local star, which we call the sun. The planets are classified based on their size and density.

There are 4 different types of planets in our solar system. The first is terrestrial planets like Earth. A terrestrial or rocky planets means that the planet is mainly composed of rocks. 


The second type of planet is gas giants like Jupiter. This means that the planet is mainly composed of hydrogen and helium and there is no solid surface.

The third type of planet is called an ice giant. Neptune is classified as an ice giant because it is mainly classified of elements heavier than hydrogen and helium, such as oxygen, and of course, ice. 

The four and final type of planet is called dwarf planets. A dwarf planet cannot be classified as a planet but is a celestial body resembling a small planet but is lacking certain features. The difference between a dwarf planet and a planet is that because the dwarf planet is smaller, it does not have enough gravitational force to pull in and accumulate material found in their orbits.

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The Sun

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The sun is a middle-age star, about 4.6 billion years old. It is the center of our Solar System. It is a nearly perfect sphere, and by far is the most important source of energy for life on Earth. It is the only thing holding our Solar System together. It accounts for 99.8% of all the matter in this Solar System. 


Even though the Sun is a average-sized star, it    can still fit around 1 million Earths. An example of a way larger star is the Betelgeuse in the shoulder of the constellation Orion; and is 400 times bigger than our Sun, which means that it could fit around 400 million Earths!

Around 75% of the sun's mass is hydrogen, then the rest is mostly helium, taking up 25%. The remaining 2% consists of heavier elements, including oxygen, carbon, iron and neon. 

The Sun fuses about 600 million tons of hydrogen into helium in a second, converting 4 million tons of matter into energy every second as a result. This energy can take up to 170,000 years to escape the sun's core, which is the source of sun's light and heat.

Also like other stars, the sun orbits around our galaxy, the milky way. It takes around 225-250 million years to complete one full orbit around our galaxy.


When viewed in space by astronauts, our sun burns white in colour.  When we see it from Earth, through our atmosphere, it burns yellow.


On the sun's surface, there are obvious black blotches called sunspots which are slightly cooler than the sun's  surface. The sun's surface temperature averages about 5500 degrees celsius and the sunspots average around 3316 degrees celsius. 

Problems and issues

We know that the sun is the only thing preventing humans from being extinct. We couldn't survive without it.


But the sun causes problems too. In late 2003, we found out how dangerous those problems could be. A huge solar flare shot highly charged energetic particles at Earth.


Airplanes had to stop flying over the North and South poles because of increased radiation. There were power blackouts in Sweden and satellites in orbit were damaged. Many other space objects like the Hubble Space Telescope had to be shut down to prevent being damaged. 



Venus is the second planet from the sun. As the second-brightest natural object in the night sky after the Moon, Venus can cast shadows and can be, on some rare occasions , visible to the naked eye in broad daylight. Venus, like Mercury, does not have any moons.

Venus has been called Earth's sister planet because of their similar size, mass, proximity to the sun, and bulk composition. But in all other aspects, it is majorly different. 

Venus has the densest atmosphere in our Solar System, consisting of 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth, or roughly the pressure found 900 metres underwater on Earth. 


Venus is by far the hottest planet in the Solar System, with a surface temperature of 462 degrees celsius, even though Mercury is closer to the Sun. The tremendous heat on Venus was the result of volcanic eruptions that released carbon dioxide in the air, creating the greenhouse effect. Scientists also think that rising temperatures caused Venus's ancient oceans to evaporate. 


Venus is covered by a layer of highly reflective clouds consisting of sulfuric acid, preventing its surface from being seen from space in visible light. It may have had water oceans in the past, but these would have vaporised as the temperature rose.

Venus is classified as a terrestrial planet because it consists of majorly rock. It's composition is like Mercury's. Venus have a silicate crust and mantle covering a nickel-iron core. 

Venus's surface is filled with large meteor craters that range in size from 2.4 to 270 kilometres across. Venus is also called a volcanic world because it has many volcanoes, and much of it's surface is covered by lava.  

Even though this sound very negative, some day, hundred of millions of years from now, Venus will begin to cool down, and oceans will form. This will help with the removal of carbon dioxide by naturally dissolving it in seawater, like Earth. Venus may then be more like Earth's twin sister.



Mars is the fourth planet from the sun, and is the second-smallest planet in our Solar System, after Mercury, and is nearly half the size of Earth. Mars is a terrestrial planet, having a similar composition as Venus and Mercury, but with an iron sulfide core.

The surface of Mars is filled with soaring canyons, scaping volcanoes, jumbled plains, magnificent polar ice caps, majestic sand dunes, and impact craters formed millions of years ago. 

Liquid water is necessary for life on Earth. But the atmosphere on Mars is too thin and the temperatures are too cold that liquid water cannot exist. Although, there are signs that underground water sometimes flows up. 

Mars has two moons: Phobos and Deimos, which appear like asteroids. They are irregular in shape and are very small compared to Earth's moon. Phobos has a diameter of 22.2 km and Deimos has a diameter of 12.6 km.

Ceres and the Asteroid belt


Ceres is the largest asteroid in the main Asteroid Belt that lies between Mars and Jupiter, but it is classified as a dwarf planet. Ceres has a diameter of 940 kilometers and has a crust that is 60 percent rock and 40 percent ice. The robotic NASA spacecraft Dawn entered orbit around Ceres on 6 March 2015.

Ceres is also the only known object in the Asteroid Belt to be rounded by its own gravity. From Earth, Ceres is too dim to see by the naked eye, even in dark skies. In January 2014, emissions of water vapor were detected from several regions of Ceres.

The Asteroid Belt is a torus-shaped region of Asteroids in between the orbits of Mars and Jupiter. The Asteroid Belt is home to around 1.9 million asteroids. Asteroids come in different shapes and sizes, and they all orbit the sun. Occasionally, Jupiter's gravity can push some Asteroids out of orbit, sending them towards the sun. When this happens, Asteroids can strike some of the terrestrial planets. 

Most of the Asteroids in the Asteroid Belt are composed of rock and stone, but some of them contain iron and nickel metals  The remaining asteroids are made up of a mix of these, along with carbon-rich materials. Some of the more distant asteroids tend to contain more ices. Although they aren't large enough to maintain an atmosphere, but there is evidence that some asteroids contain water.



Jupiter is the largest known planet in our Solar System. It is the fifth planet from the sun. Although Jupiter only has a mass of one-thousandth of the sun, it has more than 2.5 times the mass of all the other planets combined.  

Jupiter is the third brightest object in the night sky, after the moon and Venus. Jupiter is a gas giant, which means that it has no surface to stand or walk on. Jupiter also has a red hurricane three times the size of Earth that has been raging for centuries. Jupiter also has winds that rip through the skies at 640 kilometers per hour. 

Jupiter is also considered as a failed star. If Jupiter had been just a bit bigger, nuclear fires would have ignited inside it, radiating heat and light like our sun. If that had happened, we would have had 2 suns instead of one.


Days are very short on Jupiter, as it spins very quickly on its axis. A day on Jupiter is around 9.9 Earth hours and a year is11.2 Earth years. 

The atmosphere of Jupiter is composed of about 90% hydrogen, and 10% helium and there are also other elements such as methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur.  

Jupiter also has rings like Saturn, but it is too thin and faint to be seen from Earth. The rings are made of rocky material ejected from Jupiter's smaller moons. 

Jupiter's moons

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Jupiter currently has 79 known moons, and the four largest can be seen through a small telescope in a clear sky. They are called the Galilean moons because they were discovered by Galileo in 1610. 

The first Galilean moon, Io, is located closest to Jupiter. It is the fourth-largest moon in the Solar System, with the highest density, and the lowest amount of water (by ratio) of them all. Io has a diameter of 3643.2 kilometers and is the third-largest moon of Jupiter, being slightly bigger than Earth.


Io is also the most geologically active body in our Solar System, being home to more than 400 active volcanoes. This extreme geologic activity is the result of tidal heating from friction generated within Io's interior as it is pulled between Jupiter and the other Galilean moons—Europa, Ganymede, and Callisto.

Callisto is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System The surface of Callisto is the oldest and most heavily cratered in the Solar System. Its surface is completely covered with impact craters and ice. Its icy surface might be covering a sub-surface, and it might be a candidate for life in the Solar System.

The Galilean moon Ganymede is the largest moon in the solar system, and if it orbited the sun, it would have been considered a planet. Ganymede is also the only moon in our Solar System known to have a magnetic field. Ganymede also has a very, very thin oxygen atmosphere, making it a candidate for life, as Ganymede also has a sub-surface ocean. 

Europa is slightly smaller than Io, making it the smallest of the Galilean moons. It has an icy surface which is covering a sub-surface ocean. Water is one of the most important attributes to life on Earth, and Europa might have even more water than Earth, despite being smaller.

When Galileo discovered these moons, people at that time still believed that Earth was the center of the Solar System, and the Galilean moons were the first piece of real evidence that something didn't revolve around the Earth. 



Saturn is the sixth planet from the sun and is the second-largest planet in our solar system, after Jupiter. Saturn is a gas giant nine times the Earth's radius, but it only has about one-eighth of the average density of Earth. However, Saturn, despite its low density, is 95 times the Earth's size.

The interior of Saturn is made up of a core of rock and iron-nickel (silicone and oxygen). It has a deep layer of metallic hydrogen, a fluid hydrogen intermediate, and liquid helium intermediate layer, and finally, a gaseous external layer in its core. 

Saturn is considered the most beautiful planet in the Solar System because of its prominent ring feature. Now, we know that all gas and ice giants have rings, but Saturn's are the only ones that are visible from Earth. The diameter of Saturn's rings altogether spans 282 000 kilometers. There are also areas in the rings that are more than 3 kilometers thick.


Like Jupiter, Saturn has no surface to walk on, and its atmosphere is mostly made of hydrogen and helium. Also like Jupiter,  large, white, oval-shaped storms appear on Saturn. 

Saturn also spins very quickly on its axis and completes a rotation in 10.23 Earth hours. But because of its distance from the sun, it takes about 30 Earth years to complete one full orbit.

Saturn's rings reflect 70% of the light from the sun and are sometimes brighter than the planet itself. Saturn's rings are mainly composed of ice and are thought to have formed 50-100 million years ago, either from the remains of an icy moon or from an asteroid.

Saturn's moons

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Saturn currently has the most moons in the Solar System: 82. That is 3 more than Jupiter's 79 moons. Most of Saturn's moons are quite small and oddly shaped. 

Titan is the second-largest moon in our Solar System, after Ganymede, has a diameter of 5150 kilometers and is bigger than Mercury and any known dwarf planets. Titan also has an atmosphere, very low gravity, and dark liquid methane lakes with drainage channels. Scientists believe that Titan's atmosphere is very similar to Earth's early atmosphere. If so, Titan might also be one of the objects in our Solar System to harbour life. 


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Uranus is the seventh planet from the sun. Uranus is classified as an ice giant. Uranus's atmosphere consists mainly of molecular hydrogen and helium. The planet itself is composed of liquid hydrogen, icy water, ammonia, and methane. Uranus also has a molten core. 

Uranus has a diameter of 50,724 kilometers and is nearly 4 times as big as Earth. Uranus also has 13 thin rings and has 27 moons. 

What's special about Uranus is that it was hit by something gigantic long ago and now it has a 98-degree tilt to its axis. This means that the planet is basically on its side! The North Pole of Uranus is permanently facing the sun, and the South Pole is permanently facing away to space unless if it is hit by something again. 


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Neptune is the eighth planet from the sun. It is the fourth-largest planet in diameter, and also has the wildest weather in all of the planets of the solar system, with winds that blow at speeds over 2000 kilometers per hour. Neptune is 17 times heavier than Earth. Neptune is classified as an ice giant because its rocky core and the icy layer is larger compared to elements like hydrogen and helium.

Like all the gas and ice giants, Neptune doesn't have a solid surface, even though it is 17 times heavier than Earth. Neptune also has six rings surrounding it.  Despite the fact that the clouds of Neptune are very cold, around -212 degrees celsius, Neptune's rocky iron core is about the same temperature as the sun's surface, nearly 5500 degrees celsius. This internal heat is the cause of Neptune's extreme weather.

Neptune, like Jupiter, also has dark spots, or storms on its surface. The largest is called the Great Dark Spot, similar to the Great Red Spot on Jupiter, and is larger than Earth. 


Neptune was the first planet in the Solar System to be detected by calculation rather than observation. After the discovery of Uranus in 1781, astronomers realized that something was affecting the orbit of Uranus, and it was Neptune, yet it lies a billion miles farther out in space. 

Neptune spins fairly quickly on its axis, with one day being about 16 Earth hours. But since it is so far from the sun, a year on Neptune is about 164.8 Earth years. Neptune currently has 14 known moons, but since Neptune is so far from us, it could have many more that we cannot see, even with the aid of our advanced telescopes.

The Kuiper Belt

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The Kuiper Belt, pronounced Kai-per belt, is a region of our Solar System that exists beyond Neptune and stretches up to hundreds of millions of miles beyond the dwarf planet Pluto, about 20 times as wider and 20 to 200 times more massive than the Asteroid Belt.


There have been around 1000 objects discovered in the Kuiper Belt, and it is theorized that there could be up to 100,000 objects that are larger than 100 kilometers in diameter.


Spectrographic studies conducted of the Kuiper Belt have suggested that objects in the Kuiper Belt are mostly composed of ices: a mixture of light hydrocarbons (such as methane), ammonia, and water ice - similar to comets. Initial studies also confirmed a broad range of colors among KBOs (Kuiper Belt Objects), starting from neutral grey to crimson. This gives evidence that their surfaces are composed of a wide range of compounds, from dirty ices to hydrocarbons.

The Kuiper Belt will not last forever. The Kuiper Belt asteroids collide on a regular basis, so therefore instead of making a bigger body, they are slowing disappearing, grinding into dust over the course of hundreds of millions of years.



Pluto is the largest known dwarf planet in our solar system, although it was once considered as a planet. It is also one of the largest members of the Kuiper belt,