Mercury, Venus, Earth, Mars, Jupiter, Uranus, Saturn and Neptune. Currently, there are eight planets in our solar system. All these planets are divided into two categories, namely outer planets and inner planets.
So, in this article, IDN Times discuss about difference between outer planets and inner planets. There are quite a lot of differences, from the meaning to the characteristics they have. Come on, take a look!
What are the outer and inner planets?
What are the outer planets and inner planets? Reported Texas Parks and Wildlifehere are the definitions of outer planets and inner planets.
Inner planets or what are also called terrestrial planets are the four planets that are closest to the sun. The outer planets are the four planets furthest from the sun. The term for the outer planets is Jovian planet.
The inner and outer planets are bounded by the asteroid belt. This term is the name for the region of space between the orbits of Mars and Jupiter. It is called the ‘asteroid belt’ because it consists of millions of asteroids that also orbit the sun, reported Cool Cosmos.
Difference between outer planets and inner planets
The asteroid belt that forms the boundary between the outer and inner planets is only one of many signs that differentiate the two groups. Apart from their location inside and outside the asteroid belt, there are also several differences between the outer planets and other inner planets. Reported Starlusthere is a summary of seven differences between outer planets and inner planets.
1. The distance of the planet from the sun
illustration of the inner planets (commons.wikimedia/rrinsindika)
The first difference between outer planets and inner planets is the distance from the sun. In summary, the inner planets are the four planets closest to the sun. This planet is located between the sun and the asteroid belt. The four planets are Mercury, Venus, Earth and Mars.
Meanwhile, the outer planets consist of four planets that are farthest from the sun and are located outside the asteroid belt. The outer planets include Jupiter, Saturn, Uranus, and Neptune.
2. The size of the planet
illustration of planet size comparison (commons.wikimedia/ jcpag2012)
The second difference lies in size. A characteristic of the inner planets that is quite visible is that they are much smaller than the outer planets. Mercury is the smallest planet which only has a diameter of 4,879 km. Earth is the largest planet in the inner planet group with a diameter of 12,756 km.
The outer planets are larger than the inner planets. One of them is the planet Jupiter which is the largest planet with a diameter of 142,800 km. Meanwhile, the smallest planet in the outer planet group is Neptune with a diameter of 49,528 km.
3. Chemical composition of the planet
illustration of the planet Saturn (filckr.com/kevin gill)
The third difference between outer planets and inner planets is their chemical composition. The inner planets are dominated by rock and metal materials. Therefore, it is called a planet terrestrial because of its solid surface, reported Universe Today.
Meanwhile, the outer planets are dominated by gas and ice. The planets Jupiter and Saturn are made of hydrogen and helium, while Uranus and Neptune are made of methane, ammonia and water.
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4. Planetary surface temperature
outer planet illustration (flickr.com/european space agency)
The fourth difference between outer planets and inner planets is their surface temperature. Inner planets have higher temperatures because they are closer to the Sun. Well, Mercury, the closest planet to the Sun, has an average surface temperature of around 167 degrees Celsius.
On the other hand, outer planets that are farther from the sun have lower surface temperatures. The reason is, photons from the sun take longer to reach this planet. Thus, the outer planets receive little or no sufficient heat.
5. Rotation period
illustration of planetary orbits (filckr.com/nasa universe)
One of the similarities between the inner planets and the outer planets is that they all rotate. A planet’s rotation period is the time required for a planet to complete a complete rotation around its axis. This process is calculated from how long the day lasts.
This rotation period is influenced by the law of conservation of momentum which says that the angular momentum of a system will remain constant unless an external force influences it. On outer planets which consist mostly of gas, the rotation process is faster. The reason is that gas is added to the planet, thereby increasing the total angular momentum of the earth, according to reports Astronomy.
6. Period orbit
illustration of planetary orbits (rewpixel.com/rawpixel)
The orbital period of a planet is the time it takes to complete one full orbit around the sun. For example, Mercury has an orbital period of only 88 days. Meanwhile, Neptune has an orbital period of 165 years.
The reason for the different orbital periods of each planet is quite simple. The inner planets are closer to the sun. As a result, their orbital distance is shorter so the journey around the sun is shorter. The farther a planet is from the sun, the longer its orbital distance and the longer it takes.
7. Number of planetary satellites
ilustrasi satelit planet (commons.wikimedia/ck-12 foundation)
The final difference between outer planets and inner planets is their satellites. Inner planets tend to have no planets. Even if you have them, there aren’t too many of them. Mercury and Venus have no satellites, while Earth only has one and Mars has two natural satellites.
In contrast, the number of satellites between the outer planets is much different. One example is the planet Jupiter which has 79 satellites. Saturn has 82 satellites, Uranus has 27 satellites, and Neptune has 14 satellites.
Outer planets have more satellites because their gravitational pull is much stronger than that of terrestrial planets. When the solar system was formed, the outer planets were able to hold much more material so that over a long period of time they turned into satellites.
Isn’t it quite clear the difference between outer planets and inner planets? Don’t make the mistake of mentioning it, okay?
Author: Roziana Lailatul Hidayah
Also Read: 7 Brightest Objects in the Solar System, Not Just the Sun
2023-10-23 13:19:00
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