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Aardvark Communications:

A Practical Guide to Astronomy


The Wandering Planets


Comparison Table of the Planets

The Planets of our Solar System

The early Greeks described the planets as 'the wanderers' because in contrast with the stars that remained fixed relative to each other, the planets moved across the starfields at different speeds and not only that, but sometimes they seemed to stop and reverse their direction of movement. For many centuries different theories tried to explain these movements but they were all bound to fail because they still placed the Earth as the center of the solar system. Planets look like stars in the night sky, however there is one major difference; stars emit light & planets reflect light from the Sun.

Mercury

Merury is the closest planet to the sun. It is also a very hostile planet compared to Earth. During the day temperatures reach 700 deg F. During the night it will dip to a chilly 300 deg F. Mercury is made up of iron, which could come in handy if we can find a way to mine it. Mercury is also pockmarked much like the moon and scientists think Mercury is shrinking slightly every year. The average day lasts 56 Earth days and it takes 88 days to complete a year (go around the Sun).

Venus

Venus is the closest planet to Earth. When visible to us it is the brightest planet in the night sky. Venus, named after the Greek god of beauty is a very colourful planet. However its beauty is only skin deep. It is contantly covered by poisonous clouds (mostly carbon dioxide) and if we were to visit Venus, we would have to withstand a pressure equivalent to the bottom of our deepest ocean. Venus is also very hot, about 900 deg F.

Little Known Facts:Venus' day lasts longer than its year. It takes 243 Earth days to spin once, and only 225 Earth days to circle the Sun. Venus has a vlocano called Sapas Mons, 250 miles wide and almost 1 mile high.

Mars

Named after the Greek god of war, 'the Red Planet' has been the source of many theories of alien life form. These theories started when astronomers first started looking through telescopes. Observers noticed what looked like canals on the surface of Mars. These turned out to be naturally made. Mars has a barren dusty surface made up of soil and rocks. It also has the largest volcano in our Solar System. Olumpus Mons rises 25 km high and has more than one summit. Mars also has two small moons, called Phobos and Deimos.

If we had to evacuate the Earth for any reason, we could establish a 'camp' of bio-thermal domes on Mars. However, this would be very difficult to do without water, of which there is none on Mars.

Recently, scientists located a meteorite that landed in Antarctica several million years ago. Some scientists have speculated that the meteorite may contain microbes, and further, they are also "guessing" that the rock came from Mars. Confirmation remains to be seen.

Jupiter

Jupiter is the largest of all the planets in our Solar System. Its surface is not solid but rather a turbulent mixture of constant winds of gas and ice. There is a very faint ring that surrounds the planet that wasn't discovered until 1979 by the Voyager space probe. The atmosphere around Jupiter is made of hydrogen & helium. Inside Jupiter is 4 major layers:
  • A small rock core
  • Inner layer of hydrogen
  • A shell of helium & hydrogen
  • A swirling surface of icy clouds
When observing this planet, a Great Red Spot can be seen. This is a tornado that has been swirling for at least 100 yrs. It's about 40,000 km long and 100,000 km wide (talk about a twister!).
Jupiter has 4 major satellites: Castillo, Ganymede, Europa, Io.

Saturn

Saturn's greatest features are its 3 main rings. These rings are comprised of bands of ice and rock. These rings are huge but very thin. Saturn has a least 19 moons. Mimas is one of the innermost satellites and has a crater on its surface nearly two-thirds the size of its diameter. Titan is the largest satellite and is bigger than Mercury. Its atmosphere is made of nitrogen gas, and may have oceans made of liquid methane.

Uranus

Discovered in 1781 by amateur astronomer William Hershel using a home-made telescope. Made up of mostly hydrogen, helium & methane. The methane causes the planet to look green in colour from Earth. Uranus has 15 orbiting satellites. The five major ones are Miranda, Ariel, Umbriel, Titania and Oberon.

Neptune

Discovered in 1846 Neptune can not be seen with the naked eye. With a telescope it looks to have a faint green-blue tinge. It is very similar to Uranus in its size and it is surrounded by rings. Also similar, is the temperature -200 deg C. Neptune has 8 satellites that we know of. The two main ones are Triton and Nereid. Triton has a very unusual orbit. It travels in the opposite direction of the planet's own spin. It's cycle takes 680 years.

Pluto

The farthest and smallest of all the planets is Pluto. Discovered in 1930 it is very difficult to see even with a telescope. Due to its unusual orbit, Pluto sometimes is inside Neptune's orbit. This is happening now, so from 1979 to 1999 Neptune is the 'outermost planet'.

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