Mercury-It is the closest planet to the sun.It is the smallest planet.It goes around the sun every 88 earth days.A day on mercury lasts lot longer than a day on earth.Because it is so close to the sun,mercury can be very hot but at night it gets very cold.Mercury, named after the Roman messenger to the gods, is the closest planet to the Sun and the smallest traditional planet in the Solar System. It orbits the Sun in 88 days, meaning that for every year on Earth, four years have passed on Mercury. However, because it takes 59 days for Mercury spin once on its axis (one Mercurian day), it takes 176 days for the Sun to completely rise and set over the planet's horizon, compared with the 24 hours it takes for the same thing to happen on Earth. It is because of Mercury's speed across the face of the Sun that it is known as the "Messenger" planet. It's Greek equivalent is Hermes. Mercury is so small and so close to the Sun that it is almost impossible to see. With telescopes, just after dawn or before sunset, the planet can be seen as a small spot in front of the Sun surface. Hundreds of years ago, astronomers thought it was two separate objects as it could be seen twice a day. Its "morning" name was Apollo.
Venus is the second planet away from the Sun and the closest planet to Earth. It is the brightest object in the sky after the Sun and the Moon and can, in the right conditions, be seen during the day! At night, because it is so bright, it is also able to cast shadows! Venus is named after the Roman goddess of Love and Beauty although, if we look closer at Venus, at its poisonous atmosphere and deadly volcanic surface, we soon discover that there is nothing beautiful about the planet. The planet has a thick swirling cloud cover which never clears to reveal the surface. It is only through recent technology that we can see under the clouds and view Venus' landscape. The thick clouds also mean that heat cannot escape from the planet, meaning that Venus' temperature can be 480°c, so it is the hottest planet in the Solar System, even hotter than Mercury, the closest planet to the Sun! Before astronomers discovered that Venus is a planet, people believed it to be two different stars, known as The Morning Star and The Evening Star. Earth is only 612 kilometres wider than Venus and has a similar mass, volume, pull of gravity and is about the same geological age.
Earth is the third planet from the Sun and the largest of the four Inner Planets. It is the planet that you live on and is special because it is the only place in the whole Solar System known to support life. It is in the perfect position in the Solar System - not too close to the Sun and not too far away - meaning that it has the right climate for life to exist - not too hot nor too cold. It also has plenty of water, a key ingredient for all living things. In fact most of the Earth's surface (70% of it) is covered by water. Surrounding the planet is a layer of atmosphere which prevents most of the Sun's poisonous rays from reaching the surface. This atmosphere also contains oxygen which many animals (including people!) need to be able to breathe. A magnetic field also protects Earth. Earth is a planet which orbits the Sun every 365 and a quarter days, taking 23 hours and 56 minutes to turn on its axis. This is the reason that a year is 365 days long and a day is 24 hours long. It has one Moon which orbits the planet every 27 days.
Mars is the fourth planet from the Sun and the last of the four Inner Planets. Mercury, Venus and Earth are the other Inner Planets. It is the second closest planet to Earth and is about half as wide. In mythology, Mars is the Roman god of War, a name possibly inspired by the planet's red (blood) colour. Because of its colour, Mars is sometimes known as the Red Planet. The length of a day on Mars is not much longer than a day on Earth. It takes 24 hours and 37 minutes for Mars to spin once on its axis, compared to 23 hours and 56 minutes for Earth to do the same. A Martian day is often called a Sol. To complete a full journey around the Sun, Mars takes 687 days. Therefore, a Martian year is 687 days long. Mars has two small moons - Phobos and Deimos.
Jupiter is the biggest planet in the Solar System and is the first of the four Gas Giants. Earth could fit into Jupiter over 1300 times! The planet has a very strong pull of gravity and very faint rings spinning around it, just like Saturn's rings only much, much thinner. Jupiter is made up almost entirely of gas. This means that the whole planet is just like sky without any land below it. In this sky are electrical storms (lightning) and winds and hurricanes. Jupiter may have a very small liquid or solid centre which would be only about same size as Earth. This is because the pressure would be so intense at the centre that the atmosphere would feel so 'heavy' at the centre of the planet so that hydrogen molecules (tiny bits of hydrogen) would break down to form a ball of metallic liquid or solid. This metallic core is very dense and is extremely magnetic, causing Jupiter's strong magnetic field. It is this magnetic field that causes Jupiter to create twice as much heat than it receives. and, with the gravitational pull of Europa, Jupiter's second large moon, cause Io, Jupiter's closest large moon, to have the most volcanic surface in the Solar System.
Saturn is quite often regarded as one of the most beautiful and outstanding objects in the Solar System. It is a gigantic planet with huge rings surrounding it, and a moon which resembles an early Earth! Saturn is named after the Roman god of agriculture and vegetation. However, there is no actual land on Saturn for the planet to possess any agriculture or vegetation. The entire planet, like Jupiter, is made up of gas! It may have a liquid core, caused by immense pressure weighing heavily at the centre and squeezing molecules together into a liquid state, rather than a 'gassy' state, but most of the planet is one gigantic sky! The planet spins on its axis so fast that, instead of appearing round, it is more oval shaped, being wider across its centre than from top or bottom. In fact, its widest point (not including its rings) is 120,000 kilometres.
The seventh planet in the Solar System is Uranus. It was discovered by William Herschel, an English astronomer and composer, in March 1781 using a home-made telescope. The planet is named after the Greek god, Uranus, who, in mythology, ruled the heavens. The planet is the third largest in the Solar System with a diameter (width) of 51,118 kilometres (31,763 miles). It takes just over 84 years on Earth for Uranus to orbit the Sun. This is because the planet is so far away from the Sun (2,869,328,000 kilometres /1,740,200,000 miles away) meaning it has a greater distance to travel, and moves at such a slow speed because of the Sun's weaker pull of gravity. Uranus is just about visible from Earth without a telescope as a very faint star. Even close up, the Voyager 2 spacecraft, which had already visited Jupiter and Saturn and would later visit Neptune, revealed little about the planet. It was simply a gigantic pale blue ball of hydrogen, helium and methane gas (methane filters out red light, so the planet appears blue). The planet is about a third of the size of Jupiter.
Neptune is often seen as Uranus' twin planet. It is similar in size and colour, and has a similar chemical make-up. It was discovered in 1846 by Johann Gotfried Galle when scientists realised that it was difficult to predict Uranus' orbit. It became obvious that there must be something further away in space pulling on Uranus. This object turned out to be Neptune. The giant blue planet, slightly smaller than Uranus at 49,500 kilometres wide (Uranus is 52,000 kilometres wide) takes 165 years to orbit the Sun, meaning that it never completes a complete journey around the Sun during the lifetime of anybody on Earth, and since its discovery, it has only orbited the Sun once. The completion of its first orbit was as recent as July 2011. It may surprise you to know that Earth, is the next biggest planet in the Solar System, but it could fit into Neptune 60 times!