Planets of the Solar System

Planets of the Solar System

There are eight planets in the solar system, including Earth, but only four besides our own are visible to the naked eye: Venus, Mars, Jupiter, and Saturn. Mercury: The smallest of the planets is Mercury. Its diameter is less than half the earth’s.

Named for the god of the winged messenger, it is the planet closes to the sun and has no satellites. It has been believed for longtime that Mercury always turned the same side toward the sun and that the sunlit part of Mercury had a temperature hotter than 600 degrees Fahrenheit. By contrast, the temperature on the side away from the sun is thought to be -460 degrees Fahrenheit. Venus: Named for the goddess of love and beauty, Venus is almost the same size as Earth and is often called Earth’s “sister planet”.

The brightest of all planets, Venus is shadowed only by the Sun and the moon. It is the first “star” to appear in the evening sky and the last to disappear in the morning. At its brightest, Venus may even be visible during the day. Many astronomers believe that the core of Venus is largely metallic, mostly made of iron and nickel. Because of the dense carbon dioxide clouds enveloping the planet, the surface of Venus can’t be seen. Earth: Ours is the third closest planet to the sun – they are only 93 million miles apart.

Seen from space, the planet appears as a blue ocean sphere with brown and green areas marking the location of its continents. Its diameter at the equator is 7,900 miles, and its atmosphere contains 78 percent nitrogen and 21 percent oxygen, in addition to traces of water in gaseous form, carbon dioxide and other gases. By measuring the radioactive decay of elements in the Earths’ crust, scientists estimate that the planet is about 4.5 billion years old. Mars: Like Earth, Mars has four seasons, but the diameter of Mars is just a little more than half that of Earth’s, and its mass is only about a tenth of ours. Named for the god of war, Mars takes 687 days to complete one revolution of the sun.

About 80 percent of the planet is carbon dioxide. The white caps that cover its poles increase in size during the Martian winter and shrink during the summer. Martian seasons are about twice as long as Earth’s. Jupiter: Next to the sun, Jupiter is the largest and most massive object in the solar system. Named for the leader of the gods, Jupiter has a mass more than twice that of all other planets combined. A body on the surface of Jupiter would weigh 2,64 times what it would weigh on Earth. Jupiter completes a revolution every 10 hours, giving it the shortest day in the solar system. It also has 12 satellites, the largest number of any planet in the solar system.

It is perhaps most famous for its Great Red Spot, which scientists believe is a storm that has been going on for more than 300 years. Saturn: The second largest planet in the solar system, Saturn is named for Titan, the father of Jupiter and the god of sowing. It is best known for its system of concentric rings, which are not visible to the naked eye. The rings are probably composed of debris from a shattered satellite. Saturn is the least dense of all the planets but one of the brightest. Uranus: Visible by the naked eye on a dark, clear night, Uranus is unique because its axis of rotation lies almost in the plane of its orbit. The planet was discovered by the German-English astronomer William Herschel in 1781. Herschel proposed to name the planet Georgium Sidus, in honor of England’s King George III. But in keeping with the tradition of naming planets after Greek gods, it was eventually named after the father of Titan and the grandfather of Jupiter

. Uranus has five known satellites and a mass over 14 times that of Earth’s. Its temperature is thought to be below -300 degrees Fahrenheit. Neptune: Named for the god of the sea, Neptune requires 165 years to complete one revolution of the sun. Its atmosphere is made of methane, hydrogen, ammonia, and helium, and its mass is about 17 times that of Earth. The planet was discovered as a result of a mathematical prediction. Two mathematicians, John Couch Adams and Urbain Le Verrier, calculated that there must be an unknown planet more distant from the sun than Uranus because they could detect the gravitational pull on Uranus.

Pluto : (this planet used to be the 9th planet, but it is now seen as a big asteroid). There is probably little or no atmosphere on Pluto because of its extreme temperature, which is nearly -400 degrees Fahrenheit. From Pluto the sun would only appear as a bright star. While it was named for the odd of the underworld, the planet’s first two letters are also the initials of Percival Lowell, whose research on gravitational forces led him to predict the planet’s existence around the beginning of 20th century. It wasn’t until after Lowell’s death, however that the planet was discovered.