Since time immemorial, scientists have been working tirelessly to unearth what is hidden out there in space. So far, they have discovered 8 planets in the solar system. Continue reading to learn more about the 8 planets in order from the sun.
What Is a Planet?
A planet is defined as a celestial body moving in an elliptical orbit around a star.
Ultimately, a planet does three things: It has to orbit a star, must have enough gravity to create a spherical shape, and must be able to move away from any objects of the same size near its trajectory.
Why Is Pluto No Longer a Planet?
Up until 1990, everybody believed that the solar system had 9 planets. But astronomers started questioning the legitimacy of Pluto as a planet, given that it was the odd one out.
So, in 2006 the International Astronomical Union (IAU) made an extremely controversial decision to demote Pluto to a dwarf planet, arguing that it failed to meet the three important criteria the union uses to describe an ordinary planet.
In its argument, the IAU claimed that Pluto meets all the criteria except one — the ability to clear its neighboring region of other similar objects.
The IAU further argued that Pluto is on a wildly slanted, elliptical orbit far away from the sun. The union defines a dwarf planet as a celestial body sitting in a direct orbit of the Sun but hasn’t cleared its orbit of other similar objects.
History of the 8 Planets in Our Solar System
According to the National Aeronautics and Space Administration (NASA), the solar system is made up of the Sun and everything else that is bound to it through gravity, including planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets like Pluto, tens of moons, and millions of asteroids, comets, and meteoroids.
NASA further reports that outside the solar system, there are many more planets than the stars you see in the sky at night.
To date, they’ve discovered thousands of planets orbiting other stars in the Milky Way, and discoveries of more planets continue to be reported. The organization further claims that the hundreds of billions of the stars we see are believed to have their own planets.
Studies have shown that planet Earth is a mere dot in the enormous cosmos surrounded by countless stars that are accompanied by objects that perhaps have a life of their own. It is believed that the solar system was formed approximately 4.5 billion years ago from a thick cloud of interplanetary gas and dust.
According to experts, this cloud collapsed as a result of the shock wave of a neighboring star, known as supernova, that exploded. After collapsing, the cloud created a rotating, whirling disk of solid material referred to as solar nebula.
Materials farther out in the solar nebula clumped together and smashed into each other to form larger objects, some of which grew big enough to be shaped into spheres by gravity.
These objects are what became planets, dwarf planets, and large moons. Other smaller bits of the exploding star that couldn’t form planets became asteroids, comets, meteoroids, and small moons.
List of the 8 Planets in Order from The Sun
Mercury is the smallest planet in the solar system, and the one closest to the Sun. This planet is estimated to be just slightly larger than the Earth’s moon. When you are viewing the Sun from the surface of Mercury, it appears three times larger than when it’s viewed from the Earth. Additionally, the sunlight is about 7 times brighter in Mercury than on Earth.
Surprisingly, Mercury is not the hottest planet in the solar system, despite its proximity to the Sun. In fact, Venus, which is slightly farther away from the sun, is known to be the hottest planet. One day on Mercury (the time it takes for Mercury to rotate or spin once with respect to the stars) is equivalent to 59 Earth days.
And a single day-night cycle on Mercury is equivalent to 175.97 Earth days. A year on Mercury (the time the planet takes to make a complete orbit around the Sun) is equivalent to 88 Earth days.
Mercury has a rough surface, which is solid and cratered just like the Earth’s moon. The planet has a thin atmosphere consisting of oxygen, sodium, hydrogen, helium, and potassium. No human beings can naturally survive here.
Venus is practically identical to the Earth in terms of size and structure. In fact, it is commonly regarded as the Earth’s twin. However, there are many differences that exist between the two planets.
For instance, Venus has a very dense, toxic atmosphere consisting of carbon dioxide and an eternally thick, yellowish cloud of sulfuric acid that traps heat, making it the hottest planet in the solar system.
This planet also has crushing air pressure on the surface — 90 times more than that of the Earth. A day on Venus is equivalent to 243 Earth days because Venus rotates backward, with its sun rising in the west and setting in the east. Its solid surface consists of a volcanic landscape covered with vast plains, volcanic mountains, and large ridged plateaus.
Another unique thing about Venus is that it doesn’t have moons or rings. The extreme temperatures in Venus and acidic clouds make it inhabitable. Although its surface rotates slowly, its winds blow at hurricane force.
Earth is the only known planet that’s habitable by living things. It is also the fifth largest planet in the solar system and the only planet with water on the surface. The name Earth, which is about 1,000 years old, means “the ground”. It is located approximately 93 million miles away from the Sun.
Earth is made up of solid and dynamic rocks that form mountains, valleys, plains, and many more. However, the largest portion of Earth is covered in liquid water. Its atmosphere consists of nitrogen (78%), oxygen (21%), and other ingredients (1%). Earth has only one moon and doesn’t have rings.
The atmosphere on Earth forms a protective shield that protects its inhabitants from incoming meteoroids by breaking them up into tiny bits before they hit the surface.
Mars is a dusty, cold desert with an extremely thin atmosphere. It is also very dynamic with seasons, valleys, defunct volcanoes, polar ice covers, and unquestionable evidence that it has been active for a long time. This planet is one of the most explored planets in the solar system.
Mars is estimated to be about 142 million miles away from the Sun. A day on Mars takes a little over 24 hours. The planet makes a complete orbit around the Sun (one year) in 687 Earth days. It’s a rocky planet with a solid surface that was altered by volcanoes, winds, crustal movement, impact, and chemical reactions.
Because of its thin atmosphere which contains carbon dioxide, argon, nitrogen, and a small amount of oxygen, Mars is inhabitable by humans and other living things.
It has two moons named Deimos and Phobos but doesn’t have rings. Mars is commonly regarded as the Red Planet due to the iron minerals in the soil.
Jupiter is the largest planet in the solar system. In fact, it is estimated to be twice as huge as all the other planets in the solar system combined.
The planet’s conspicuous lines and swirls are cold, breezy billows of ammonia and water, floating in an air-filled with hydrogen and helium. Its unmistakable Great Red Spot is a massive storm that has continued to rage for hundreds of years. This storm is larger than the Earth’s planet.
Jupiter is estimated to be located approximately 484 million miles away from the sun. It rotates once about every 10 hours (a Jovian day) but takes about 12 Earth years to complete one orbit of the Sun (a Jovian year). Jupiter doesn’t have an Earth-like surface, instead, it’s filled with gases, mostly hydrogen and helium.
Jupiter has over 75 moons and a faded ring system. This planet doesn’t support life, but there are oceans beneath some of its moons’ crusts that are suspected to be able to support life.
Saturn is the second-largest planet in the solar system. It’s decorated with thousands of gorgeous ringlets. Although it is not the only planet that has rings consisting of pieces of ice and rocks, its rings are more remarkable and complex. Like Jupiter, Saturn is just a ball full of gases, mainly helium and hydrogen.
Saturn is located approximately 886 million miles away from the Sun. It takes about 10.7 hours to rotate on its axis once — a Saturn “day” — and 29 Earth years to orbit the sun.
The planet has 53 moons (which have been confirmed) and 29 others that are awaiting confirmation. There is no life in Saturn, but scientists suspect that some of its moons might have conditions that are favorable to living things.
Known as the sideways planet, Uranus orbits on its side. It is just an ice giant planet, estimated to be about four times bigger than the Earth. This planet has 27 known moons and some spectacular rings.
This planet is located approximately 1.8 billion miles away from the Sun. Uranus is not habitable. It rotates east to west, just like Venus.
Uranus takes about 17 hours to rotate once (a day), and about 84 Earth years to complete an orbit of the Sun (a year). It mainly consists of hot, dense fluid of water, methane, and ammonia. This material is in icy form and sits above a small rocky core. Its atmosphere consists of molecular hydrogen, atomic helium, and methane.
Neptune is the most distant planet in the solar system. It is a dark, cold planet belted by supersonic winds. This planet is not visible to the eye. It is located about 2,8 billion miles away from the Sun.
Neptune takes about 16 hours to rotate once (a day), and about 165 Earth years to complete an orbit of the sun (a year). Its atmosphere consists of molecular hydrogen, atomic helium, and methane. Neptune has 14 confirmed moons that are named after sea gods and goblins in Greek mythology.
It has at least 5 rings and 4 ring arcs. These rings and arcs are just clumps of dust and rubbles formed by the gravity of the nearby moon. Neptune does not support life as we know it.
Mnemonics on How to Remember the Eight Planets in Their Correct Order
If you are looking for an easy way to remember all the eight planets in their correct order from the Sun, you can use these mnemonics.
If you have always had trouble listing the 8 planets in order from the Sun, I believe this article has made it easier for you. And if you can’t remember the correct names, you can just use simple mnemonics.