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Explore the Solar System [Copy link] 中文

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Post time 2012-1-17 12:59:29 |Display all floors
The SunOur star, 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 amounts 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.
Read about eye safety during solar eclipses on the NASA website.


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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.

Find out more about the other planets in the Solar System
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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 mainly composed 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.

Photo: A false-colour view of Venus taken by the Galileo probe. This photo was coloured blue to show details in Venus's clouds. (NASA/JPL)
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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 scientists sometimes call the Goldilocks zone. Its distance from our star means it is neither too hot, nor too cold to support liquid water - thought to be a key ingredient for life. Astronomers are searching for rocky planets like ours in the Goldilocks zones of other stars.

BBC Earth has exciting videos about volcanoes, earthquakes and more.

Photo: The Earth rising behind the Moon taken by the Apollo 16 crew (NASA
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Mars


Mars was among the first bodies in the Solar System to be viewed through a telescope. Early astronomers saw faint surface features along with evidence of changing seasons and speculated about an advanced Martian civilisation. Though these ideas are comical today, the search for more primitive life continues.

NASA's Mariner and Viking probes in the 1960s and 1970s found a cold, apparently lifeless planet with huge volcanoes and canyons and evidence of past surface floods.

More recently, six-wheeled rovers have confirmed that water ice exists below the surface.
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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 liquid metallic hydrogen in its interior 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.

Photo: A true colour mosaic of Jupiter taken by the Cassini probe (NASA/JPL/Space Science Institute)

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Saturn


Saturn, the sixth planet from the Sun, has beautiful rings composed of ice particles. It is the second largest planet 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.

Saturn is mainly composed of hydrogen and helium and does not have a solid surface. It has 25 satellites that measure at least 10km in diameter - the largest, Titan, is the only moon in the Solar System with a substantial atmosphere.

Saturn's interior is thought to contain fluid metallic hydrogen - a substance that cannot be studied directly because it is not possible to recreate the very high temperatures and pressures at which it is predicted to form.

Photo: Saturn taken by the Cassini probe (NASA/JPL/Space Science Institute
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