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It is hard to comprehend the enormity of our Universe. Our Sun is only one of billions of stars in our galaxy, known as the Milky Way. But beyond the Milky Way, there are billions of other galaxies, too. Collectively, all these galaxies, along with the vast amount of space found in between them, are called the Universe. Solar System The Sun The star at the center of our solar system. It has a diameter of 1.39 million kilometres and the temperature of the visible surface is 5780 K. Planets 9 planets orbit the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto Moons There are now over 100 known moons in the orbit around the planets of the Solar System. Some, like Earth and Pluto, have just one companion while Jupiter has over 60. Comets Rocky-icy bodies in elliptical orbits travel through the Solar System developing a large tail of gas and dust in their orbit as they draw closer to the Sun. There are at least 150 perio...

Introduction to the Universe Solar System   The Solar System is a collection of planets, moons, asteroids and comets and other rocky objects orbiting the Sun. The Solar System is believed to extend out to at least 150 000 million km from the Sun, although the planets are all found within about 6000 million km. Our Solar System is thought to have formed 4.6 x 10 9 years ago from a vast, rotating cloud of gas and dust known as the solar nebula. As the solar nebula rotated, its gravity began to attract gas and dust towards the centre, eventually forming our Sun. The Sun The Sun is the powerhouse of the Solar System. Without it, life on Earth simply would not exist. Despite burning its hydrogen fuel for the best part of 5 billion years, the Sun is still only half way through its life cycle. The study of the Sun, its environment and how the material it discharges interacts with other worlds in the Solar System is of great interest to us all. ...