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Properties of Outer Planets in the Solar System

Grade 8
Jun 12, 2023

Properties of Outer Planets


Our planet Earth is a part of the solar system, which has 8 planets revolving around a star named the Sun. Additionally, there are natural satellites revolving around most planets in the solar system. There are other celestial bodies called asteroids, meteors and comets, which are all a part of the solar system. In this session, we are going to look at some of the planets called the outer planets and their properties.


The planets closest to the Sun–Mercury, Venus, the Earth and Mars are called the inner planets. And the rest of the planets are called the outer planets.

Inner and Outer planets


Astronomical Unit:

The average distance between the Earth and the Sun is called 1 astronomical unit. It is a unit of distance used to measure the distance between planets and the Sun in the solar system.

1 AU = 1.496 x 1011 m

Astronomical Unit

The planets beyond the inner planets are termed the outer planets. These are the Jupiter, Saturn, Uranus and Neptune. They come after the asteroid belt, which lies between Mars and Jupiter.

Planetary data for the Outer planets



Jupiter is the largest planet in our solar system. It is like a mini solar system with a composition similar to that of the Sun and numerous moons revolving around it. 4 of its moons were observed by Galileo Galilei in the year 1610 and were named “Galilean moons” – Lo, Europa, Ganymede and Callisto.

When Jupiter is looked at through a moderately sized telescope, its moons are seen. Also, a Great Red Spot is seen, which is a giant storm system in the atmosphere of the planet. It has rings made up of small pieces of icy material, which orbit the planet.

In 1995, the spacecraft Galileo dropped a package of instruments into Jupiter’s atmosphere. Tremendous atmospheric pressure caused the instruments to fail after only one hour. Small amounts of water vapor and oxygen are detected in Jupiter’s atmosphere, but most of it is composed of hydrogen and helium. Jupiter’s clouds, which are seen when viewing it through a telescope, are largely made up of ammonia.



Saturn is believed to be the most beautiful object in the night sky. It is the second largest planet in the solar system. It is a gas giant composed mostly of hydrogen and helium. It has the most extensive and complex ring system in the solar system. The rings are mostly composed of rock and ice and can just fit into the distance between the Earth and the Moon. The material in the rings ranges in size from grains of salt to houses.

Saturn has more than 30 known moons, Titan being the largest one is similar to mercury in size. The atmosphere of Titan is nitrogen-rich, which might also include the gases such as methane and ethane. In 2004, the Cassini spacecraft was the first to explore Saturn’s rings from orbit. In 2005, the European Space Agency’s Huygen’s spacecraft entered Titan’s thick atmosphere.

Scientists are interested in studying Titan because of its thick atmosphere. Also, some areas on Titan contain relatively pure water-ice, while other areas contain organic compounds.



Uranus and Neptune are both gas giants that were discovered with telescopes. Uranus gets its blue-green color from methane gas above the deeper cloud layers. It is so distant from the Sun that it takes 84 years to complete one orbit. Uranus is unusual in that its axis of rotation is nearly parallel to the plane of its orbit around the Sun.

It rotates on its side as it orbits the Sun. It has 27 known moons and a series of rings. The atmosphere of Uranus is composed of hydrogen and helium with a liquid core composed of water, methane, and ammonia.



Neptune was the first planet located using theoretical predictions rather than through ordinary observations of the sky. The clue to Neptune’s existence was that Uranus did not orbit the Sun precisely as expected. Neptune has 13 known moons and several rings. Discovered in 1846, it has not quite finished one orbit of the Sun since its discovery. Neptune’s atmosphere is made up of the gases such as hydrogen, helium, and methane. It is methane that gives the planet its blue color.


Dwarf Planets:

The solar system also includes at least 3 dwarf planets, namely, Ceres, Pluto and Eris. A dwarf planet differs from a planet because it has not cleared the neighborhood around its orbit. Ceres is a part of the asteroid belt and Pluto and Eris are part of the Kuiper belt.

Dwarf planets

Questions and Answers:

Match the Following:


Answer: i—d, ii—e, iii—a, iv—b, v—c.

Properties of Outer Planets


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