In the Solar System, the inner planets are those that are located closest to the Sun, while the outer ones are those that are farthest from it. The inner planets are Earth, Mars, Venus, and Mercury, and the outer ones are Saturn, Jupiter, Neptune, and Uranus.
But in addition to their location relative to the Sun, the inner and outer planets have other characteristics and differences.
Inner planets: characteristics and examples
The inner planets are those that are closest to the Sun. But why do we call them inner and outer? What marks the line of what is inside and what is outside? The reality is that the line that marks the inner planets from the outer ones is the asteroid belt , a kind of ring formed by a multitude of astronomical objects, most of them asteroids. Here we explain what the inner planets are .
Examples of inner planets
- Mercury : it is the smallest lower planet, also the one closest to the Sun. That is why the temperatures are very high, which makes it impossible to have an atmosphere. For the same reason, we can rule out that it can harbor life.
- Venus : beyond the Sun and the Moon, Venus is the planet that shines the most in our sky. Although it is not the planet that orbits closest to the sun, it is Mercury, Venus is the hottest planet, with a surface completely covered by lava. There is great volcanic activity on that planet, which has created a very dense atmosphere that makes it impossible to directly observe the planet.
- Earth : it is the only planet that currently has all the characteristics for there to be life. The Earth has an atmosphere composed of nitrogen and oxygen, huge bodies of water and a great climatic variation that favors the existence of life.
- Mars : it has an almost imperceptible atmosphere, which means that it cannot retain solar radiation and that there are temperature variations of more than 100ºC. As a curiosity, on Mars we find the highest volcano in the Solar System, Olympus, which is more than 25 kilometers high.
Characteristics of the inner planets
In addition to sharing a certain location with respect to the Sun, the inner planets share certain characteristics, for example, their size, the composition of their atmosphere or the composition of their nucleus. Here we explain the characteristics of the inner planets :
- Compared to the outer ones, the inner planets are small.
- The inner planets have a high density, between 3 and 5 g / cm³.
- The inner planets are also known as rocky, since their surface is made up of silicates, that is, the minerals that make up rocks.
- The inner planets rotate on their slow axis. For example, that of Mars and Earth is 24 hours, while for Venus it is 243 days and that of Mercury is 58 days.
- They are also known as telluric planets, since their nucleus is made up of stone or rock.
- The only ones that have an atmosphere are Mars, Venus and Earth, and they all emit less energy than they receive from the Sun.
The outer planets are those that are farthest from the Sun, they are located beyond the asteroid belt. The outer planets are also known as giant planets, since they are larger. On the other hand, their atmospheres are usually much denser than those of the inner planets. Due to the fact that their composition is gas, they are also known as gaseous planets. Here we explain what the outer planets are :
Examples of outer planets
- Jupiter : it is the closest to the Sun of the outer planets, in addition, it is the largest planet in the Solar System, in fact, its matter is greater than that of the rest of the planets together. It has 17 satellites and a ring system that is invisible from Earth.
- Saturn : it is the second largest planet in the Solar System, in addition, it is the only one with rings that can be observed from our planet. It has more than 25 satellites, for example Titan, the only satellite in our system that has a remarkable atmosphere.
- Uranus : With a faint blue surface due to the high amount of methane, Uranus is the only planet that rotates on its side, that is, it circles in its own orbit.
- Neptune : it is the planet furthest from the Sun in the entire system. Its surface is ravaged by very strong winds and it has 13 satellites, Triton being the largest of them. It also has rings, however, from Earth they are very difficult to distinguish.
Characteristics of the outer planets
The outer planets not only share the fact that they are further from the sun, they also have some common characteristics such as their composition, atmosphere or size. Here we explain the characteristics of the outer planets :
- Although they are further from the Sun, they are all within the solar system.
- The outer planets are also known as gaseous planets , since they do not have a solid surface.
- The outer planets are also known as giant planets , since they are much larger than the inner planets.
- Most of the planets discovered outside our system have a composition similar to that of the outer planets.
- The magnetic fields of the outer planets are very high.
- They are also known as Jovian planets , a name that comes from Jupiter.
- The outer planets have a very fast rotation on their axis , for example, Jupiter does it in less than 10 hours, Saturn does not arrive at 11 hours, Neptune slightly more than 16 hours and Uranus almost 17 hours and a quarter.
- In the orbits of the outer planets we find many rings and satellites .
- The cores of Neptune and Uranus are made up of ice.
Inner and outer planets: differences
Now that you know what they are and their characteristics, below we explain the differences between inner and outer planets :
- The inner planets are also considered rocky planets, since their surface is solid. For their part, the outer planets are called gaseous planets because that’s how their surface is.
- The inner planets are small-sized planets, while the planets are called giant planets because their size is so much larger.
- The inner planets have a slow rotation,.
- Unlike the outer planets, which have a very fast rotation, the rotation of the lower planets is slow
- The outer planets have rings and many satellites and moons, unlike the inner planets that have no rings and few satellites.
- The inner planets are also called telluric, since their core is very hot. In contrast, the core of the outer planets is made of ice.
- Unlike the inner planets, whose atmosphere is made up of helium and hydrogen or nitrogen and CO2, that of the outer planets is made up of helium and hydrogen alone.