There are eight planets that make up our solar system in the Milky Way Galaxy. All planets orbit around the sun. Initially, it was thought that we had nine planets, when Pluto was discovered in the 1930s. However, in the 1990s Pluto was demoted to the status of a dwarf planet rather than a true planet. The eight planets are outlined below, from largest to smallest:
1. Jupiter - diameter of 142,800 km (11.2 times bigger than Earth)
Jupiter is the biggest planet in our solar system. Its diameter measures 142,800 km. It is so gigantic that all other planets in the solar system could fit into Jupiter. It is the fifth planet from the sun. Its name was derived from the Roman king of gods. Its atmosphere is composed of gasses mainly hydrogen and helium. Jupiter’s surface is made of an ocean of liquid hydrogen.
Jupiter appears to have white, yellow, thick red and brown clouds. These clouds move around the planet at high speeds in the opposite direction as the planet spin on its axis. The largest of these storms is the Great Red Spot which move around the equator at high speed that resembles a hurricane.
Jupiter has the strongest magnetosphere of all other planets, nearly 20,000 times that of Earth. Jupiter rotates on its axis faster than any other planet in just less than 10 hours. Jupiter has three faint rings composed of dust particles which result from the impact of comets and asteroids. The planet revolves around the sun once in a period of 11.86 Earth years.
2. Saturn - diameter of 120,660 km (9.5 times bigger than Earth)
Saturn has a diameter of 120,660 km and is ranked second regarding planet size. This radius is not inclusive of its rings. It is easily visible to the naked eye and is the sixth planet from the sun. Its discovery is not credited to any one person. It was named after Saturnus the Roman gods. It rotates on its axis every 10 hours and 34 minutes and orbits around the sun in 29.4 Earth years. Its atmosphere has three layers, the first layer is composed mostly of ammonia ice, and the second layer is made of water ice, while a mixture of hydrogen and sulfur makes up most of the third layer.
Saturn is mostly made of hydrogen. It has thin and extensive rings made up of particles of ice and small chunks of carbonaceous dust. These particles are thought to be results of asteroids, moons, and comets breaking apart in Saturn’s vicinity. The planet is 1,424,600,000 kilometers away from the Sun. Saturn has 62 known moons and is the flattest planet largely because of its low density and fast rotation speed.
3. Uranus - diameter of 51,118 km (4.0 times bigger than Earth)
The existence of the planet Uranus is credited to a British astronomer William Herschel. It was an unprecedented discovery made on March 13, 1781. Uranus is the seventh farthest planet from the sun. Uranus is the third largest planet with a diameter of 51,118 km. Its name was derived from the ancient Greek deity of the sky called Ouranos. It takes Uranus 17.24 Earth days to spin on its axis. Uranus orbits around the Sun in 84 Earth years. Uranus and Venus are the only two planets out of the eight known planets that follow a clockwise path while orbiting around the Sun.
80% of the surface of Uranus is composed of ice. Uranus has a pale blue color because of the presence of water, ammonia, and methane ice on its outer atmosphere. It has a hydrogen and helium layer underneath this upper atmosphere. The planet has a core of iron and magnesium silicate.
4. Neptune - diameter of 49,528 km (3.8 times bigger than Earth)
Of all known planets, Neptune is the most distant from the Sun. It was discovered on September 23rd, 1846, by Johann Gall. The discovery was facilitated by prior information from a French astronomer Urbain Le Verrier and another independent British astronomer named John Couch Adams. It orbits the Sun in 164.79 Earth years and has 14 moons has five faint rings.
Neptune is a gas planet made mostly of hydrogen, helium, and methane. The methane in the atmosphere absorbs red light in substantial quantities such that Neptune appears to be the color of azure blue. The name Neptune can be traced to Roman mythology where Neptune was the name given to a god the Romans believed to be the sea. The planet’s core is mainly made of rock. It has a massive violent storm called the Great Dark Spot. The climate on Neptune is very active with large storms and winds swirling around it at high speeds. Only one spacecraft has been sent to Neptune in 1989 called the Voyager 2.
5. Earth - diameter of 12,756 km
Earth is the fifth largest planet in the solar system. It is also the third closest planet to the Sun. Earth is the only planet in the universe that harbors life - at least as far as we know. Around 71% of Earth is covered in ocean waters. The sun is the source of all energy for all living beings on Earth.
The Earth is technically a sphere. It has a diameter of 12,756 km. The deepest known point on Earth is the Mariana Trench, where the highest point is found at Mount Everest. Around 7.6 billion humans currently live on the Earth. The vast majority of the species to have ever existed on Earth are extinct - the majority of them were never described.
6. Venus - diameter of 12,104 km (95% the size of Earth)
Venus, the sixth largest planet, is very similar in size to Earth. It has a diameter of 12,104, which is 95% the size of Earth. Venus is well-known for shining bright in the sky and occasionally being visible from Earth. Over history, many spaceships have visited Venus.
Venus is a very hot planet with an average temperature of around 460 degrees Celsius. This, combined with a dry surface and an atmosphere primarily composed of carbon dioxide means that Venus is rather ill-equipped to host life. Most of Venus is covered with lava.
7. Mars - diameter of 6,779 km (about half the size of Earth)
Mars is the fourth planet from the sun, and also the second smallest planet. It has a diameter of 6,779 km. Also known as the Red Planet, much of the surface of Mars is composed of rock. Mars has a very thin atmosphere with very small traces of oxygen. Mars has two moons.
Water may have once existed on Mars. Although it has been suspected that life on Mars may have at one point been possible, scientists have not discovered any evidence of this.
8. Mercury - diameter of 4,849 km (38% the size of the Earth)
Mercury is the smallest planet in the solar system, but one of the most dense. It has a very large core which contributes to this density. It has a total diameter of around 4,849 km. Comparatively speaking, Mercury is a mysterious planet. Less than half of its surface has been mapped by scientists on Earth.
Although Mercury is the closest planet to the sun, it is not a warm planet due to its inability to lock in heat. Like Earth, it is a rocky planet.
What's the Biggest Planet in the Solar System?
With a radius of 69,911 kilometers, Jupiter is the largest of the 8 planets orbiting our sun.
Biggest Planets In Our Solar System
About the Author
Benjamin Elisha Sawe holds a Bachelor of Arts in Economics and Statistics and an MBA in Strategic Management. He is a frequent World Atlas contributor.
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