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The planet on which we live is called the Earth.
Our planet is constantly moving around the sun, and each year, the Earth travels all the way around the sun.
But there are many other planets that also travel around the sun.
Together with the sun, the planets, and various other bodies, the Earth is part of our “solar system.”
The planet that is closest to the sun is Mercury.
Mercury is extremely hot, and it is much smaller than the Earth. The second planet from the sun is Venus.
Venus is about the same size as the Earth.
Venus is also very hot.
The Earth is the third planet from the sun.
The Earth is unusual among the planets, because it has such a large moon.
The Earth is bigger than the moon, but the moon is still quite large.
It takes about one month for the moon to travel around the Earth.
The fourth planet from the sun is Mars.
Mars is known for its red colour. Mars is smaller and colder than the Earth.
Mars has two very small moons.
After the planet Mars, there are many small bodies called the asteroids.
These rocky objects are much smaller than planets.
The first four planets are all made of rock and metal.
The remaining planets, however, are mostly made of frozen gases.
The fifth planet is called Jupiter.
Jupiter is the largest planet.
It has many moons that travel around it, and it also has a large red spot.
The sixth planet is called Saturn.
Saturn is the second-largest planet, and it is famous for the wide “rings” that surround it.
These rings are made up of many smaller objects that are found in the same area.
The seventh planet is called Uranus.
The eighth planet is called Neptune.
These planets are also gas giants, but they are smaller than Jupiter and Saturn.
Both Uranus and Neptune are so far from the sun that scientists only discovered these planets during the past few hundred years, using telescopes.
The other planets had all been visible to curious people for many thousands of years.
The ninth planet is called Pluto.
Pluto is very small, and it is much more rocky than the gas giants.
Some scientists believe that Pluto is not really a planet at all.
They suggest that Pluto is the largest of many asteroids that are found at the edge of the solar system.
The solar system is a vast place.
So far, people have not travelled beyond the moon.
But perhaps someday, human astronauts will visit the other planets of our solar system!
我们居住的星球叫做地球。我们的星球不停地绕着太阳转动，每年，地球都会绕太阳一周。但还有许多其他的行星也在绕着太阳转动。地球与太阳、行星和各种其他天体一起，构成了我们的“太阳系”。离太阳最近的行星是水星。水星非常热，而且比地球小得多。离太阳第二近的行星是金星。金星的大小与地球差不多。金星也很热。地球是离太阳第三近的行星。地球在行星中很不寻常，因为它有一个如此大的月亮。地球比月亮大，但月亮仍然相当大。月亮绕地球一周大约需要一个月的时间。离太阳第四近的行星是火星。火星以其红色而闻名。火星比地球小，也更冷。火星有两颗非常小的卫星。在火星之后，有许多被称为小行星的小天体。这些岩石物体比行星小得多。前四个行星都是由岩石和金属构成的。然而，其余的行星主要由冻结的气体构成。第五颗行星叫做木星。木星是最大的行星。它有许多卫星绕着它转，而且它还有一个大红斑。第六颗行星叫做土星。土星是第二大行星，它以环绕它的宽阔“环”而闻名。这些环由许多在同一区域发现的较小物体组成。第七颗行星叫做天王星。第八颗行星叫做海王星。这些行星也是气体巨星，但它们比木星和土星小。天王星和海王星离太阳太远了，以至于科学家们在过去几百年里才用望远镜发现了这些行星。其他的行星在几千年来一直被好奇的人们所看到。第九颗行星叫做冥王星。冥王星非常小，而且比气体巨星更像岩石。一些科学家认为冥王星根本不是一颗行星。他们认为冥王星是太阳系边缘发现的许多小行星中最大的一颗。太阳系是一个广阔的地方。到目前为止，人类还没有到过月球以外的地方。但也许有一天，人类宇航员会访问我们太阳系的其他行星！