The Sun
The Sun
is a star that lives at the centre of the Solar System. Its huge
gravity holds the planets in place.
The planets
The planets all revolve around the Sun. There are eight in total
- Mercury, Venus,
Earth, Mars,
Jupiter, Saturn,
Uranus and
Neptune.
Moons
Moons rotate around their parent planet. Earth has one
moon, but
some planets have over 50. Only Mercury and
Venus do not have
any moons.
Asteroids
Asteroids are rocky bits of debris up to 1,000km (620 miles)
across. Most live in the asteroid belt between Mars and Jupiter.
They are the remnants from early planets that collided and were
torn apart.
Comets
Comets are dirty snowballs of ice and dust that revolve around
the Sun in long orbits. When they approach the Sun they heat up,
leaving a trail of gas behind them, which looks like a tail.
Recent comets to fly-by
the Sun include Halley, Hale-Bopp and Ikeya-Zhang.
LOCAL HISTORY
Our Solar System began
forming about 4.6 billion years ago from a swirling gas cloud.
Over time, the gas cooled and clumped together to form large
bodies called 'protoplanets'. The 'left over' material became
comets, roaming silently through the Solar System.
Eventually after 100
million years, the enormous ball of gas at the centre of the
cloud overheated and exploded in a huge nuclear reaction. The
Sun was born.
People of the ancient
world observed the movements of the planets and thought they
were wandering stars. This is why the Greeks gave them the name
planetes
or 'wanderers'. |
From the Earth
You can sometimes spot the planets in the night sky from
Earth.
Unlike the Sun and the other stars, they don't produce their own
light. They shine because they are reflecting the Sun's light.
THE PLANETS
The rocky planets
The four planets closest to the Sun are:
Mercury
Venus
Earth
Mars
These are called the 'rocky' or 'terrestrial' planets. They are
small by planetary standards and made of similar materials to
the Earth.
The gas giants
The next four planets are:
Jupiter
Saturn
Uranus
Neptune
They are known as the 'gas giants'. They all have rings and lots
of moons. The gas giants are made up mostly of hydrogen, helium,
frozen water, ammonia, methane, and carbon monoxide.
The Dwarf Planets
The International Astronomical Union redefined the term planet
in August 2006, so Pluto is now classified as a dwarf planet.
There are two other dwarf planets in the solar system, Ceres and
Eris.
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