آزمون آنلاین انگلیسی 3 - انگلیسی 3 | آزمون شماره 10399

The solar system is the Sun and the objects that travel around it. The Earth is a part of the solar system because it also travels around the Sun. The Sun is a star similar to the other stars in the sky, but it is much closer to the Earth. The Sun is mostly a big ball of gases composed mainly of hydrogen and helium. There are seven other planets that travel around the Sun, too. These planets, in order, include Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. The Earth is located between Venus and Mars. The path a planet uses when traveling around the Sun is oval-shaped and is called an orbit. Each of the planets in the solar system takes a different amount of time to orbit or travel around the Sun. The four inner planets, Mercury, Venus, Earth and Mars are made of rock containing many different minerals. The four outer planets, Jupiter, Saturn, Uranus, and Neptune are mostly made up of different gases. Jupiter is mainly helium, hydrogen and water. The four outer planets also have rings that encircle them with Saturn having the most rings. 

Other objects in space include the moons of six planets. A moon is a celestial object (object in space) that orbits another body in space. There are approximately 173 moons throughout the solar system. The Earth has a single moon, Mercury and Venus have none, and the planet with the most moons is Jupiter with 63. Not far behind Jupiter, is Saturn with 62 moons. The asteroid belt is another object in the solar system. The asteroid belt contains irregularly shaped bodies called asteroids which are believed to be left over from the beginning of the solar system, 4.6 billion years ago. The objects are rocky and irregular in shape, and some may be hundreds of miles across, but most of the asteroids are very small.

What is the difference between the Sun and other stars of the universe?