The Solar System
We live in a solar system--a place where planets move in invisible paths, called orbits, around a star in the middle.
Our star is the Sun. It is the biggest and strongest object in our solar system . Its giant size gives it more gravity, or pull, than anything else.
Gravity keeps evething around the Sun from floating away. This powerful force holds planets, moons, asteroids, comets, meteors, and more in place. Each has its own special orbit around the Sun.
The Sun is the only star in our solar system. It is a giant ball of hot, glowing gas. Its huge size makes it so powerful that the Sun holds our solar system together.
The Sun is so bright and hot that it also makes all the light and heat for all the planets in our solar system.
Mercury is the closest planet to the Sun.
It orbits the Sun in only 88 days. That is faster than any other planet.
Mercury is hard to see because it is so far away.
The best times to look for Mercury are before the sun rises or sets.
As a rocky inner planet, Mercury has a solid surface.
During the day , it gets super hot. At night, it gets super cold. Mercury is too hot and too cold for us.
Venus is the second planet from the Sun. Venus spins slowly backwards compared to the other planets. This means that the sun rises in the west and sets in the east.
It is the hottest planet in our solar system. A layer of thick clouds covers Venus like a blanket, trapping super high heat.
Sunlight bounces off Venus' clouds. This makes it the brightest planet in our solar system.
Earth is the third planet from the Sun. It is the largest of all the rocky, or terrestrial, planets.
Earth is also the fifth biggest planet in the solar system.
Most of Earth is covered with water. There is so much water, Earth looks like a blue marble in outer space.
Many planets have atmospheres, but only Earth's is safe to breathe.
Moon--A satellite of the earth
The moon is smaller than Earth, which gives it less gravity. Gravity holds things down, which gives them weight. This means everything weighs less on the moon. One hundred pounds (45.4kg) on Earth is abount the same as 16 pounds (7.3kg) on the moon.
There is no air or water on the moon, so there is no weather like rain or snow or wind.
Mars is the fourth planet from the Sun. It is a rocky planet like Earth, but much colder because of its thinner atmosphere.
Mars is nicknamed "The Red Planet" because it is covered in red dust. There is a metal called iron in rocks on Mars. When the iron rusts, it turns red and dusty.
( Scientists think Mars is more like Earth than any other planet in our solar system. They believe Mars used to have rivers, and perhaps an ocean, a very long time ago. )
Jupiter is the fifth planet from the Sun. It is the biggest planet in the solar system.
Jupiter's surface is an ocean of many different gases and water.
Saturn is the sixth planet from the Sun. It is the second largest planet in our solar system.
Saturn is best known for its big , bright rings. These rings are made from billions of pieces of ice, dust, and rock that orbit Saturn. Some pieces are as tiny as a speck of dust. A few pieces are as big as mountains.
Uranus is the seventh planet from the Sun. It looks blue and green from methane gas covering its surface. It is the coldest of all eight planets in our solar system.
Like Saturn, Uranus has rings. But these rings are not as easy to see because they are much thinner. They are made from billions of pieces of dust.
Neptune is the eighth planet from the Sun. It has wild and windy weather .
Neptune is a very dark and very , very cold planet.
Neptune is bright blue because of methane gas in its atmosphere.
名称来源：木星（a.k.a. Jove; 希腊人称之为宙斯）是上帝之王，奥林匹斯山的统治者和罗马国的保护人，它是Cronus （土星）的儿子。
( 40年前，在学地理的时候，书中学到介绍太阳系中的九大行星是：水星（Mercury）, 金星（Venus）, 地球 ( Earth), 火星 ( Mars ), 木星 ( Jupiter ), 土星 ( Saturn ) , 天王星 ( Uranus ) , 海王星 ( Neptune ), 冥王星 ( Pluto ). 后来在一元店买了一本科普书，上面介绍的太阳系是八大行星。为什么呢？于是就去网上查了一下。原来冥王星于2006年时在布拉格举行的第26届国际天文学联会通过决议，冥王星被移出九大行星行列，降级成为矮行星。因为冥王星的质量和体积都在不断的“缩水”，即越变越小。还有冥王星做不到清除轨道附近的其他物体。所以冥王星就被排出了太阳系。自此太阳系只剩八大行星。觉得小科普知识介绍得很好，所以就转摘了下来。）
---知识介绍来自科普书《The Solar System》. 而名称的来源介绍来自网络。