WHY ARE SOME PLANETS SO BIG???

LARGEST PLANETS OF THE SOLAR SYSTEM-

The largest planets on the solar system are the planets Jupiter and Saturn.Both planets have distinct bands around them with stripes.Saturn can be recognized easily by its rings.Uranus,uniquely tilted sideways,and the blue Neptune , the coldest of the outer planets,are also much larger than the inner planets.The outer planets are so big because they are comprised mainly of gases,such as helium and hydrogen.These planets have a solid core ,which is surrounded by liquid or frozen gas.This reason why they are also known as 'gas giants'.

WHY DOES SATURN HAVE SO MANY RINGS??

Although the rings of Saturn can be seen clearly with a normal telescope and have been known for 350 years,nobody known exactly how they were formed.Scientists are still trying to learn more about them.The ring system has a diameter of 278,000 km, but each only a few kilometres thick.The rings are not solid 'bands', but are believed to be made of varying sizes of comets,asteroids,and shattered moons that broke up before reaching the planet.They revolve around Saturn at different speeds.

WHY DOES JUPITER HAVE SO MANY STRIPES??

Jupiter rotates very fast on its axis,once every 10 hours.This has formed a pattern of stripes in its atmosphere,which runs parallel to the equator.The lighter zones are warm,rising masses of clouds,and the dark ones are cold,descending clouds.This pattern is disturbed by storms.One of these,the 'large red spot' ,is huge and can be seen from the Earth.Jupiter is not only the biggest but also the heaviest planet.It has more than 60 moons.Four of them were detected by the Italian astronomer Galileo Galilei with a telescope as early as 400 years ago.

WHY DOES URANUS LIE 'ON ITS SIDE'??

The impression that Uranus is lying 'on its side' arises from the fact that its axis of rotation is not vertical to its orbit around the sun,as in the other planets of the solar system.It is so strongly tipped that it lies almost parallel to its orbit.The probable reason for this is a collision with another heavenly body.This also probably gave rise to the narrow rings. Uranus goes around the sun once in 84 years.Since its axis of rotation is lying on one side,the poles point alternately in the direction of the sun every 21 years.There is then summer for 21 years and on the opposite is winter.

WHY IS IT VERY COLD IN NEPTUNE??

It is extremely cold on Neptune:the ground temperature is around -220*C.The reason for this is that it is far away from the sun,almost double the distance than its neighbour Uranus.As a result,it hardly gets any heat from the sun.Because of its blue colour, the eighth planet of the solar system was named after the Roman god of the sea,Neptune.The blue colour does not indicate liquid water,but instead its atmosphere is made of hydrogen and helium.

HOW DO WE KNOW THE 'OUTER PLANETS' SO WELL??

Much of what we know about the gas giants comes from the observations made with telescopes-with the ones that are present on the Earth as well as with the Hubble space telescope.They provide very clear pictures of the outer planets.Many pictures are transmitted to the Earth by the space probes.The most well known of these probes are Voyager 1 and Voyager 2.which started in 1977.They flew in the direction of Jupiter and Saturn,where they took the first exact pictures of the Saturn rings.Voyager 2 then flew past Uranus and Neptune for a 'big tour' of the space taking advantage of the 'slingshot' effect of the gravitational force of Saturn.As of today,both the probes have left our solar system.

DID YOU KNOW THAT????

• MANY VOLCANOES ARE ACTIVE ON THE JUPITER MOON Lo, WHICH EMIT YELLOW AND RED GLOWING LAVA RICH IN SULPHUR.
• THE ' GREAT RED SPOT' ON JUPITER IS THE OLDEST KNOWN CYCLONE.IT IS A GIANT STORM THAT IS KNOWN TO HAVE EXISTED SINCE AT LEAST THE 17TH CENTURY WHEN IT WAS FIRST SEEN.