Outer Planets of Solar System

Study Material > Geography

Outer Planet or Gas Giant

As we have discussed earlier that scientists have divided different regions of solar system according to the characteristics of the planet.
Inner planets include terrestrial planet and outer planet includes gas giants. Density of terrestrial planets are more then gas giants planets as terrestrial planet were mainly composed of rocks and gas giants are having large mass made up of gas.
In this chapter we will discuss about gas giant.
Scientist referred these planets as gas giant because of their gaseous composition.
These gas giants’ planets are different from inner planets in different aspects like outer planets have gaseous composition; they have rings around them and are very large in comparison to terrestrial or inner planets.
Jupiter is the largest among the entire solar planet.

Jupiter

Jupiter occupies the fifth position among the planets of solar system. And is one among the gas giant planets (Jupiter, Saturn, Uranus, Neptune are gas giant planet).
Jupiter is the name of one of the Roman God.
Jupiter is very bright and occupies fourth position in brightest object in night sky after sun, moon, Venus.
Jupiter contains 93 % hydrogen and 7 % helium.
Jupiter is very big in comparison of Earth and is 318 times greater than Earth in terms of mass.
Jupiter is having enormous heat which is produced inside it and it gives more heat then it receives.
Jupiter’s four large moon also called Galilean moon after their discovery by Galileo are Io, Europa, Ganymede and Callisto.
Space probe which visited Jupiter werePioneer-10 in 1973, Pioneer-11, Voyager-1, Voyager-2 and Ulysses.
The spacecraft Galileo also orbited Jupiter for several years.
Jupiter is having a great Red Spot which scientists believe to be a giant spinning storm in Jupiter’s atmosphere. Its size is almost double the size of Earth.
Jupiter has 67 known satellites. This is largest among solar planets. It is considered that due to huge gravitational pull Jupiter has captured these satellites.

Saturn

Saturn occupies sixth position from the Sun and in size it occupies the second-largest in the Solar System, after Jupiter.
In Roman the god of agriculture is called Saturn.
Like Jupiter, Saturn has about 75% hydrogen and 25 % helium with traces of water, methane, ammonia and rock.
Its density is least among planets of solar system and its specific gravity is 0.7 which is even less than that of water.
Saturn is most famous for its rings around them. Its two prominent rings ( A and B) and one faint ring (C) can be seen from the Earth.
These rings are composed from a large number of rocks which orbits around the Saturn in an independent orbit. These rocks are irregular in size from millimetre to kilometre.
Space probe Pioneer 11, Voyager 1 and Voyager 2, Cassini (a joint NASA / ESA project) visited Saturn.
Saturn has 62 known satellites. This is next to Jupiter for having large number of natural satellites.

Uranus

In Greek Uranus is God of Sky. Uranus occupies seventh position from sun among solar planets.
In size it is third largest among solar planets however its mass is less then Neptune. Hence by size it is third largest and in mass it is fourth largest.
Chemical Composition of both Saturn and Neptune are similar and are different from other gas giants i.e., Jupiter and Saturn. That’s why scientists distinguish Uranus and Neptune as a ice giant.
Uranus spins on its axis almost parallel to the ecliptic. Due to this odd fact Uranus often called as lying or sleeping planet of the Solar system which is a unique characteristics among itself.
Its atmosphere has about 83% hydrogen, 15% helium and 2 % methane.
Uranus looks blue in colour because methane which is present in its upper atmosphere absorbs red colour of Sun’s light.
Uranus is also having rings composed of rocks orbiting it.
Uranus has 27 known satellites.

Neptune

Neptune occupies eighth position among solar planets. In size it is smaller than Uranus but in mass it is larger than Uranus.
In Roman Neptune is the god of sea.
Neptune has 14 known satellites.
Space probe Voyager 2 has visited Neptune.
Neptune's blue colour is also due to absorption of red light by the methane of its upper atmosphere.
Neptune has also rings around them but their composition is not known because it is difficult to analyse them from the Earth due to their very far distance as compared to other plantes.

Kuiper Belt

These belt exists beyond gas giant region of the solar system it includes dwarf planet Pluto. This belt also holds asteroids and short period comets.

Pluto

According to the definition set by International astronomical Union (IAU) in 2006. it a celestial body is defined as a planet when it:

According to above definition Pluto doesn’t qualifies to be a planet as its size is too small. It encroaches the orbit of Neptune for a considerable time.
Because of its small size it is classified as a Dwarf Planet. And is second largest Dwarf planet in the solar system.
Pluto is named after Roman God of underworld.
Pluto has only one moon named Charon. In fact size of Charon is almost similar to the size of Pluto. That’s why scientists always referred Pluto as twin planet

Some Important facts about Planets

Biggest planet	Jupiter
Biggest satellite	Gannymede
Blue planet	Earth
Green planet	Uranus
Brightest planet	Venus
Brightest planet outside solar system	Sirius (Dog star)
Closest star of solar system	Proxima centauri
Coldest planet	Neptune
Evening Star	Venus
Farthest Planet from Sun	Neptune
Planet with maximum number of satellite	Jupiter
Densest Planet	Earth
Fastest rotation in Solar System	Jupiter
Morning star	Venus
Nearest planet to earth	Venus
Nearest planet to sun	Mercury
Red planet	Mars
Slowest revolution in solar system	Neptune
Slowest rotation in solar system	Venus
Smallest planet	Mercury
Smallest satellite	Deimos
Earth’s twin	Venus
Only satellite with an atmosphere like earth	Titan
Fastest revolution in solar system	Mercury
Hottest planet	Venus

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