Explore the Solar System

Sun

The Sun makes up 99% of all the mass in the Solar System. Its core is so dense and hot that normally repellent nuclei fuse together in nuclear reactions that produce vast quantities of energy.
The Sun is mostly hydrogen (its main fuel) and helium, and radiates charged particles called solar wind across the Solar System. Phenomena such as solar flares and sunspots are evidence of the Sun's strong magnetic field, which changes on a roughly 11-year cycle.

Mercury

The innermost planet in the Solar System is a dense, heavily cratered world that takes about 59 Earth days to fully rotate on its own axis as it travels on its 88-day journey around the Sun. It is possible to see Mercury from the Earth without a telescope or binoculars though its closeness to the Sun's bright light can make it difficult to spot.
Photographed and studied at close range by the Mariner 10 and Messenger probes, Mercury is blasted by solar radiation and is not thought to be a likely place for life to flourish.

Venus

Venus, the second planet from the Sun, is an extreme place - hot and dry with surface pressures over 90 times higher than the Earth's and a super thick atmosphere composed mainly of carbon dioxide. Because the surface is hidden by sulphuric acid clouds and the planet is similar to the Earth in size, astronomers speculated for many years that Venus might be a lush world full of life.
It is now thought possible that the Sun's heat boiled away early oceans on the planet triggering a planet-warming runaway greenhouse effect that turned Venus into a hellish place.

Earth

Earth, the third planet from the Sun, is unique in the Universe as it is currently the only planet known to support life. It has a single natural satellite, the Moon, and is the fifth largest planet in the Solar System.
Earth's distance from the Sun is thought to be one of the key reasons why it is home to widespread life. Our planet occupies what astronomers call the Goldilocks zone. Its distance from our star means it's neither too hot, nor too cold for living creatures. Astronomers are searching for rocky planets like ours in the Goldilocks zones of other stars.

Mars

Mars was among the first bodies in the Solar System to be viewed through a telescope. Early astronomers could see faint surface features along with evidence of changing seasons and speculated about an advanced Martian civilisation.
NASA's Mariner and Viking probes in the 1960s and 1970s found a cold, apparently lifeless planet with intriguing geology that hinted at past surface floods.
More recently, six-wheeled rovers have confirmed that water ice exists below the surface and looked for evidence of past microbial life.

Jupiter

Jupiter, the largest planet in the Solar System, has a volume equal to more than 1,000 Earths. The fifth planet from the Sun is called a gas giant because it has no solid surface, being mainly composed of hydrogen and helium. It is believed to have a liquid metallic hydrogen core that generates the planet's intense magnetic field.
Powerful storms such as the centuries-old Great Red Spot travel in bands across Jupiter. Its many satellites include the moons Io, Europa, Ganymede and Callisto.

Saturn

Saturn's complex ring system of ice particles sets it apart from the other planets. The sixth planet from the Sun is the second largest in the Solar System, yet it is the least dense - it would float in water if there were a bathtub large enough to hold it.
The planet is composed mainly of hydrogen and helium and doesn't have a solid surface. Saturn has 25 satellites that measure at least 6 miles (10km) in diameter. The largest of these is Titan, the only moon in the Solar System to have a substantial atmosphere.
  

Uranus

The seventh planet from the Sun was first correctly identified as a planet in 1781 by William Herschel.
Uranus may have been struck by a planet-sized object early in its life and knocked onto its side. Consequently, Uranus's axis is tilted 98 degrees compared with the Earth's 23.5 degrees.
Like the other gas giant planets, Uranus has no solid surface. It gets its bluish surface colour from tiny frozen ammonia crystals. The atmosphere is thought to be mainly hydrogen and helium. Uranus has only been visited once, by the Voyager 2 probe.

Neptune

Neptune, the outermost planet in the Solar System, can't be seen from Earth without a telescope or binoculars. It is covered by icy, bright blue methane clouds that whip around the globe at speeds of more than 700mph (1,100km/h).
Though its diameter is four times that of the Earth's and it is 17 times as massive, it is less dense and doesn't have a solid surface. Eleven moons orbit Neptune, the largest of which is Triton.
Photo: View of Neptune composed of images taken by the Voyager 2 probe (NASA)