The Nine Planets

The Inner Planets

• The four planets closest to the Sun are Mercury, Venus, Earth and Mars. All four of these planets are made up of a rocky material and therefore are called the terrestrial planets. These planets are also known as the inner planets.

Mercury• Mercury is the closest planet to the Sun,

and therefore it gets sunlight that is 10 times brighter than the Earth. Mercury does not have an atmosphere to help trap the heat it receives from the Sun, so it loses all of its heat at night dropping to – 180 degrees Celsius. Mercury’s daytime temperature is at a sweltering 400 degrees Celsius.

• Mercury is rarely seen in our night sky because it is so close to the Sun. When we do see Mercury it is generally at sunset and at sunrise.

Venus• After the Sun and the Moon,

Venus is the brightest object that we can see in the sky because it is so close to our planet Earth. Also, the atmosphere on Venus is very thick and light it receives from the Sun is reflected to us. Venus’s atmosphere is made up from mainly carbon dioxide. This gas acts like glass of a greenhouse and keeps the surface of the planet hot enough to melt lead.

Earth

• Life has grown on Earth because the atmosphere on this planet is perfect for beings to have evolved. Earth’s atmosphere is mainly made up of nitrogen, oxygen, and water vapour. There is a small amount of ozone in our atmosphere and this is what filters some of the damaging radiation from the Sun.

• Water from lakes, oceans and rivers covers approximately 70% of planet Earth. The rest of the Earth’s surface is covered by soil, which allows for the growth of vegetations and habitat from land creatures. Earth is changing every day by several environmental factors, such as volcanoes, earthquakes and pollution.

Mars• Mars is one of the

brightest planets in the sky and is sometimes referred to the RED Planet because of the reddish ting it casts. This reddish colour is caused by the rust coloured soil.

• Mars is very dry and barren but there is evidence that Mars was once covered with volcanoes, glaciers, and flood waters.

The Outer Planets

• The remaining 5 planets in our solar system are known as the outer planets; Jupiter, Saturn, Uranus, Neptune and Pluto. The first 4 of these planets are also known as the Gas Giants. Their atmosphere consists mainly of hydrogen and helium. These planets appear to lack solid surfaces. The outer most planet, Pluto, is unique among the outer planets.

Jupiter

• Jupiter is the largest planet of all of the planets. Its diameter is 11 times larger than Earth’s diameter. As well, its mass is greater than the masses of all the other planets combined.

• Jupiter is also a very bright object in the night sky because of its size and the large amount of light reflected by its clouds. Jupiter’s most interesting features are the coloured bands and the Great Red Spot. Jupiter has approximately 16 moons and sometimes you are able to see 4 of these moons by using binoculars.

Saturn

• Saturn is the second largest planet but it is the least dense of all the planets with a possibility of no core. Saturn’s atmosphere is cloudy and windy . Saturn’s average temperature is – 180 degrees Celsius.

Uranus

• Uranus’s diameter is 4 times larger than Earth. Its atmosphere is made up of mostly hydrogen, with some helium and methane. This planet has winds that blow up to 500 km/h. In our night sky Uranus looks like an extremely faint star.

Neptune • From Earth Neptune is

barely visible with the use of a telescope. Neptune has bright blue and white clouds and a dark region – the Great Dark Spot – that appears to be the center of a storm. Neptune has at least 8 moons and thin rings orbiting around it.

Pluto• Pluto is unusual

because it is not a gas giant and it does not seem to be terrestrial. The motion of Pluto’s orbit suggests that Pluto may have been one of Neptune’s moons at one time. Pluto has a moon itself, called Charon.